Wednesday, February 29, 2012

**No Updates Posted 2/29**


Due to a very busy schedule, I will unfortunately not be able to post updates on the blog today.

Thursday, 3/1 Update: I will be able to post an update today. I am currently working on an updated 5-day forecast and a March Outlook, which has been delayed until 10 PM EST (Eastern Standard Time), and a discussion which will be posted shortly afterwards.

Feb 28, 2012 Brief Update


Tonight - Tomorrow: Rain Near Coast, Mix To Rain Inland


There have been some changes with the outlook for tomorrow, as the storm continued to trend north on the models today, with some not showing much, if any accumulations for the entire area. Although some frozen precipitation is expected from NYC and further north/west for a brief time in the late morning, perhaps as brief as only a couple of minutes or lasting up to an hour or two, but the only places in the area to see snow last longer with more accumulations will be in interior southern CT away from the coast and interior SE NY, where 1 to 2, locally 3 inches of snow are expected, with snow/sleet changing over to rain by the afternoon in SE NY and the evening in CT. In the immediate NYC area, mostly rain is expected other than a brief period of non-accumulating light snow in the late morning, especially north/west of the city. Long Island will mostly see rain, but it is not out of the question that northeastern parts of Long Island see a little snow at first. Light rain will continue to fall through Wednesday night and Thursday at times, with highs reaching the lower to mid 40s for most places on Thursday. Stay tuned for storm updates tomorrow afternoon and evening.

Taking a quick look at the longer range, the next storm will move through on Saturday. Temperatures returning into the 50s along with rain are expected, with colder and drier conditions returning for the weekend and late week. There appears to be a potential for a more significant warm surge going into next week, which will be discussed in more details with tomorrow's update.

Tuesday, February 28, 2012

Feb 27, 2012: Rain NYC, Mix Inland Wednesday


Forecast Highlights:


- Stormy Wednesday: Rain in NYC, Snow/Mix to Rain Inland
- Up to 3 inches are possible in SE NY/southern CT
- Storm followed by another one for Saturday, warmth and rain return
- Drier, colder by end of weekend into early week


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With a weak low pressure staying well to the north of the area, today brought partly sunny skies and warmer temperatures, with highs peaking in the lower to mid 50s in SE NY/NW NJ and the upper 50s to near 60 degrees in NE NJ and most of NYC, although colder temperatures were observed near the coast, where JFK up to Long Island and southern CT had highs in the upper 40s to lower 50s.

The latest radar to the left shows that precipitation associated with the weak storm is starting to move out of the region, with skies expected to clear tonight into tomorrow morning. The next storm will quickly follow, however, with rain returning to NYC by Wednesday. This storm will contain an element that not many storms this season have had: snow, with accumulations in the interior parts of the area and the possibility of some flakes in NYC itself.


Tomorrow's Outlook:


Tuesday will bring mostly sunny skies to the area with colder temperatures, reaching the mid 40s across the area. Parts of the immediate NYC area may reach the upper 40s but staying below 50 degrees.


Wednesday - Thursday: Snow Inland, Rain Near Coast


The previous discussion mentioned how a storm was expected for this time frame, and although it appeared colder, there was still uncertainty. With the energy for the storm moving onshore today, it was better sampled, and the models corrected several features that yesterday's models had which caused them to change their outlook from a colder/snowier one to a warmer outlook. Yesterday's models took the primary low pressure through Michigan with a secondary low pressure forming near the Delmarva Peninsula, which seemed to be a less likely solution given the very large distance between the two areas. With stronger confluence and a stronger high pressure, the storm started out with more snow in NYC and a significant snow event north of NYC. Today's models, however, are already stronger, further north and more amplified with the storm for the short range, and with slightly weaker confluence, the whole storm is further north and warmer than yesterday's models, with a primary low track through northern Michigan and a secondary low forming not too far south of Long Island. Although this supports a warmer solution than yesterday's models, the amount of cold air damming in place as a result of the high pressure in place is still not certain, leading to some uncertainty with the exact rain/snow boundary lines.

With tonight's update, I sided in between the warmer and colder models; the GFS is likely too warm and underestimating the cold air in place. The latest models offer conflicting signals, with the CMC showing plain rain for southern CT and the NYC area, while the NAM, GFS and from early indications the UKMET as well trending colder with at least a 2-4 hour period of snow possible in NYC. Perhaps the 0z NAM may have been overdone with the cold air, but given this year's history of the models failing to settle on a solution even 36 hours away from a storm, it's still uncertain whether the northern or southern scenarios verify. For now, I went in between, but this forecast is not a final one and is subject to slight north/south shifts with tomorrow's update.

At this time, the latest expectation is for precipitation to develop in the late morning hours. With temperatures cold enough, most of the area should start out with a brief period of snow, possibly in the form of a moderate burst of snow near and north/west of NYC. Surface temperatures, however, will limit accumulations, if any, for NYC and its immediate north/west suburbs. Further inland, a longer period of snow is expected, but with the storm aligned in a NW-SE type snow line, interior southern Connecticut is likely at this time to see the most snow in the area, with over 3 inches possible. By the evening, the area should change over to rain except for higher elevations inland, which may see some freezing rain but with no significant ice amounts, and as the secondary low moves offshore, occasional showers will continue through Thursday with highs reaching the lower to upper 40s across the area.

As previously mentioned, this is still a preliminary forecast, and is subject to some changes with tomorrow's final forecast. Uncertainty focuses on the boundary of the rain/snow line and the more significant snow accumulations. It is possible that a north trend is correct and most of the area will see very little snow. However, should a trend to a colder storm start, with some of the 0z model runs coming in colder, the forecast may be adjusted to a colder one with some more snow in NYC prior to the changeover and more accumulations inland. Stay tuned for an update on the storm on Tuesday afternoon.


Longer Range Overview:


The latest models bring in another storm on Saturday, with the latest models bringing a strong storm through the Great Lakes with heavy rain for the area, temperatures getting close to 60 degrees, and even thunderstorms. This scenario, however, seems odd given this pattern, as not a single storm this winter took a track straight through Quebec while bringing in temporary blocking near Greenland in the way that most models depict this storm. In addition, the storm on Thursday night which brought snow to southern Connecticut at one point was also modeled to cross the Great Lakes with warm temperatures and heavy rain, just as Wednesday's storm was before it became apparent it would bring snow to New England. This storm will still bring rain due to the lack of any feature to keep it suppressed, but at this time I am going with a cooler, weaker and not so wet storm on Saturday, although there will still be a storm in the region on that day. Colder and drier conditions will return by the second half of the weekend into the early week. Stay tuned for more details on the longer range outlook.

Monday, February 27, 2012

Feb 27, 2012 Noon Update


4:50 PM: Yesterday's updated 5-Day Forecast added an increased risk of accumulating snow for most of the area; the latest model guidance, however, is quickly catching onto a trend with the storm in the Midwest before it reaches the region that was not seen before, with a stronger and further north storm in the Midwest tomorrow, along with less confluence than originally expected, which strongly favors a trend which, as with countless other cases during this non-winter, once again significantly reduces the chance for snow in New York City.

The latest 5-Day Forecast, updated this afternoon, removed the mention of snow in NYC other than a brief 1-2 hour period in the late morning when light snow could mix with the rain. Light snow accumulations are expected to be limited to interior southern CT, interior SE NY and parts of NW NJ. For now, 1-3 inches is a likely accumulation range, but is still subject to change, and should the latest trends continue, the potential 1-3 inch range may be too high. Tonight's update will discuss why the models changed with the storm in more details and why there will not be much, if any snow for NYC and its immediate north/west suburbs with this storm.

Sunday, February 26, 2012

Feb 25, 2012: Rain, Wintry Mix Return Wednesday


Forecast Highlights:


- Warmth returns Monday, 55-60 degrees in NYC
- Storms return Wednesday-Thursday, Saturday
- Wintry mix again Wednesday? Colder scenario is possible


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Behind the surprise snowstorm for Thursday night which brought accumulations as high as 5 inches in parts of southern Connecticut, locally heavy showers moved through yesterday evening associated with a developing coastal low pressure, with today bringing widespread windy conditions across the area, with winds gusting up to 40-50 mph across parts of the area, especially in Long Island where gusts in the 50-60 mph range were more frequent. Snow squalls were observed this evening as well with an area of moderate snow squalls moving through northern NJ, NYC and Long Island.

The latest radar posted above shows that the storm has cleared the region, with clearing skies expected for tonight into tomorrow. Warmth will briefly return for Monday with temperatures getting close to 60 degrees near NYC, but temperatures will quickly cool down afterwards, with the next storm returning on Wednesday. The Wednesday storm is still uncertain, but there is a possibility that a wintry mix may once affect parts of the area.


Tomorrow's Outlook:


A drier and sunnier day is expected for the area tomorrow with a high pressure moving in, resulting in mostly sunny skies for the area. Temperatures will be slightly cooler, in the upper 30s to lower 40s across the area, with a NW wind expected.


Next Week: Watching Mid Week Storm


Monday will be the warmest day of the week as a weak storm stays well to the north of the area with no precipitation, instead bringing partly sunny skies and a warmer air mass. Temperatures will reach the mid to upper 50s across the area, and in the warmer case scenario it is not out of the question that NYC gets close to 60 degrees. Tuesday will slightly cool down but with temperatures still reaching the mid to upper 40s, along with mostly sunny skies.

With a more active pattern starting to develop compared to the unusually dry and quiet pattern the area observed in February, with parts of the area still not having reached 1 inch of precipitation for the entire month so far, the next storm to affect the area will be on Wednesday and Thursday. The models yesterday and 2 days ago showed a heavy rain event with warm temperatures for the region, but as with the storm late last week when the models also had a similar solution in the medium range, today's models backed further south and weaker towards a potential significant snowstorm in parts of the Northeast, setting up for what is likely to be yet again a complicated and difficult forecast for the mid week storm. Given the trends with this pattern and the confluence in the Northeast preventing the storm from moving northeast, the current suppressed storm solutions are more likely to verify than the original warm storm idea, and for tonight's update I am siding with the southern solutions, but how far south the storm comes is still uncertain.

The storm is expected to come in two parts; the first part will be front end precipitation moving into the cold air in place on Wednesday afternoon, resulting in widespread frozen precipitation in parts of the Northeast. Less precipitation is expected for Wednesday night, with an inverted trough-like feature to move through the region on Thursday. Should the storm bring frozen precipitation to the area, the best chance for that will be with the front end precipitation on Wednesday. The southernmost model run today was the 12z ECM, which even had accumulating snow in NYC, and a significant snowstorm for southern/central New England. The other models today also gradually trended south and colder, with the latest GFS run showing a wintry mix for the interior parts of the area, and the latest 0z CMC run showing moderate to even significant snow accumulations in Orange County, NY and in interior southern/central Connecticut.

Given the set up in place, I am leaning with the colder scenarios at this time, while adding snow and sleet in the 5-Day Forecast north and west of NYC. There is still uncertainty, however, as it is possible that the storm could still end up further north, with mostly rain for the area. Another possible scenario is that the storm continues to trend colder and more suppressed, in which case accumulating snow would affect the rest of northern NJ and NYC, with a heavier snow potential for the interior parts of the area, although this is the snowiest outcome possible with this set up. This colder solution is not guaranteed, and it is possible that a warmer and rainy scenario verifies, but based on the latest trends, the potential is there for frozen precipitation, potentially accumulating, in the interior parts of the area, and I will continue to monitor this potential over the next couple of days. Stay tuned for more information on this storm.


Late Week - Weekend Overview: Cooler temperatures will briefly return, although the next storm will approach the region during the weekend. The latest models show a rain event for Saturday and possibly for Sunday with warm temperatures, but while a snowstorm is unlikely, considering how the long range models were considerably off with their solutions for the last couple of storms, changes are expected for this time frame, and a less rainy and colder outcome is a possibility. More information will be posted as details become clearer.

Saturday, February 25, 2012

Feb 25, 2012 Evening Update


6:05 PM: Snow Squalls Moving Through

Light to moderate snow squalls are currently moving through parts of the area, specifically in northern NJ, NYC and Long Island. Although a dusting of snow at most is expected, the snow will be moderate at times, resulting in lowered visibility, accompanied by moderate wind gusts.

The next update will be posted tonight focusing on the storm for late next week and another possible storm around next weekend.

Friday, February 24, 2012

Feb 24, 2012 Storm Updates


11:40 AM: Reviewing Last Night; Strong Winds Tonight


Following what was perhaps the most difficult forecast of the year due to a lack of consistency in the short range, the storm last night did end up producing a last minute snow/sleet accumulation for parts of the area as expected last night; the original expectation from most of the models as of Wednesday night for last night was still for rain with perhaps light snow/sleet mixing inland. The changes made yesterday did end up generally accurate in terms of the accumulation amounts, as a narrow zone did report 1-3 to locally 4 inch accumulations, but that band ended up not too far south of last night's map; Sussex county to SE New York, into coastal southern Connecticut and further inland observed widespread 2-4 inch amounts last night, with light snow/sleet making it towards the I-80 corridor in NJ and parts of NYC and Long Island; one town in Suffolk county even reported half of an inch of snow/sleet. My forecast from last night was not completely accurate, and it would've also been very difficult to make a spot on forecast given all of the lack of agreement from the models in the short range and the dependence on the radar and other short range forecasting tools, but considering all of the uncertainty, the forecast was not completely off, as the zones ended up approximately 30 miles or so south of where I had them in my map last night.

Either late this weekend or sometime next week, I plan to post a review of the forecasting for this storm, along with its impacts in the area. The model guidance did not have a good handle on the storm, even in the short range, and only 12-24 hours before the storm places that were modeled to have the most amount of snow, from east central New York into Massachusetts, barely had any snow as most of it stayed to their south. In fact, just 3 days before the storm the potential was there for temperatures to reach 55-60 degrees in parts of the area. That boundary of temperatures is now well to the south of the area, and temperatures are expected to struggle reaching 40 degrees today, failing to pass that mark in parts of the area.


Forecast For Tonight: The southern Mid Atlantic is currently under a Moderate Risk of severe weather by the SPC (Storm Prediction Center), an appearance that is not common during the winter months, especially in this part of the United States. With the temperature boundary well to the south of the area, temperatures will surge into the upper 70s and even 80 degrees in parts of Virginia today as severe thunderstorms begin to form and intensify later this afternoon. Severe weather parameters are favorable for severe activity and perhaps some tornadoes, with LI down to -5/-6, CAPE up to 1250, and bulk shear up to 60-70 knots. A secondary low pressure should form along the warm front later today when the severe thunderstorms form in the Mid Atlantic, and begin to move up the coast as it intensifies and becomes the main low pressure. As the low moves up the coast, the storms from the Mid Atlantic will become more widespread, forming a larger area of rain along with the coastal low. Some of the storms in the Mid Atlantic, although non severe, should reach New Jersey later today, and parts of the area may see briefly heavy rain this evening. The rain will then move to the north/east of the area by tonight with clearing skies expected.

The biggest concern for the area, however, is the winds from the storm. Although the warm front will not cross the area, there is a tight pressure gradient setting up just behind the storm, and the models are showing a strong signal for strong wind gusts today, stronger than the rest of the wind events of the season so far. While it will not be very windy all the time, the potential is there for widespread gusts in the 45-55 mph range across the area tonight as the coastal low exits, with gusts perhaps up to 60 mph, locally above 60 mph, in parts of Long Island and southern Connecticut. In an update I will make to the Weather Alerts page shortly, I will also issue a High Wind Watch for the eastern half of the area, which may be upgraded to a warning later today depending on any changes in the storm. Windy conditions will continue tonight with gusts still reaching the 40 mph range at times, with windy conditions returning again tomorrow with winds gusting again up to 45-50 mph, locally up to 55-60 mph especially towards Long Island.

The next update will be posted on Saturday, 2/25, with an update on the rain storm and possible warmth for late next week.

Feb 23, 2012: Unexpected Snow/Sleet Tonight


Forecast Highlights:


- Snow Finally Returns; 1-3 inches possible in northern areas tonight
- Temperatures struggle to get above 40 degrees on Friday
- Briefly windy Friday night; chilly, dry and mostly sunny for the weekend
- Next larger storm possible late next week


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With a warmer air mass still covering the region, today brought mild temperatures once again, with most of the area seeing highs in the lower to mid 50s inland and the upper 50s to lower 60s across the rest of the area. In a typical winter, these temperatures would be considered unusually warm, but these much warmer than average temperatures have been so frequent this winter that they are barely as notable as they typically would be.

Despite the current warmth, much cooler temperatures will return tomorrow. The model guidance struggled once again today with handling the storm for tonight, and unexpectedly changed the outlook to shift the snow zone tonight much further south, with accumulating snow and sleet expected in the northern half of the area tonight.


Tonight - Friday Night: Sudden Change In Forecast


Forecasting storms in the short range is typically supposed to be an easy task; the models are supposed to have converged on a single solution with minor differences, the radar and observations are generally close to the models, and a single forecast can be made with high confidence. The models, however, have had a terrible handle on this storm, and even now, literally hours before the storm is about to begin, are still not sure how to handle the storm. Two days ago, the potential was there for parts of the area to exceed 60 degrees; with the latest changes, not only will temperatures struggle to even pass 40 degrees, but apparently an accumulating snow/sleet event is hours away for the northern parts of the area.


Storm Analysis: The original question yesterday was regarding the location of the warm front and how far north/south it would end up. With the storm currently south of what yesterday's models showed, it is evident that the warm front will stay to the south of the area, with the tight gradient from 45 to 70 degrees in a short distance instead taking place towards southern New Jersey and Delaware. With the warm front staying to the south of the area, temperatures will stay in the 30s to mid 40s across the area tomorrow. The biggest change has been with the location of tonight's precipitation, however; the models earlier today had the moderate snow focused from about east central New York towards Massachusetts and southern New Hampshire/Vermont, while bringing a 40 degree rain for the area. In a matter of just 2 runs, less than a day before the storm will start, a significant south trend took place on most of the models, most notably the NAM and CMC, which with their latest runs show a brief period of heavy snow/sleet for most of northern New Jersey, southeastern New York, and southern Connecticut. With the short range models, the HRRR and RR also keep the storm south with the heaviest accumulations in southern Connecticut, with 2 to 4 inches, while the RUC is sticking with a northern scenario which appears to be too far north, as NYC barely even sees any rain on that model. The GFS is currently the northernmost model, but it was the slowest to catch up to the south trend with the storm, and also does not have a pronounced transition to a secondary low as the NAM has, which appears to have a better handle on the overall formation of the secondary low as will be discussed in more details below.

The second part of the forecast is regarding the formation of the secondary low. The GFS currently has the least emphasis on this development, although it continues to slowly trend towards a stronger signal of a secondary low developing earlier. The 18z NAM was the most bullish with this development, showing moderate to heavy rain for the area late on Friday evening, quickly intensifying into a major northern New England snowstorm by Saturday. The 0z NAM run slightly backed down, although it still develops the secondary low earlier than the GFS, with the CMC somewhat similar to the NAM as well. At this time, it does not appear that a strong storm should quickly develop in time to bring significant impacts for the area, although locally heavy rain is possible on Friday evening. This aspect of the storm though is still slightly uncertain as the models once again do not have a good handle on this, despite this development barely 24 hours from now, although huge changes are not expected with the Friday evening outlook.


Forecast For NYC Area: This is probably the most difficult forecast I've made this winter, especially due to the conflicting signals from the models for the storm despite it being only hours away. As a result, this is not a high confidence forecast, although after reviewing the set up, I have at least some level of confidence in the changes in the forecast.

Precipitation should start to fall across the area towards at least 2 AM west of NYC and 2-3 AM east of NYC. When the storm starts, temperatures will still be slowly dropping, ending up in the upper 30s to lower 40s across most of the area, starting out as light rain as a result. Moderate to locally heavy precipitation is expected with the front end of the storm around 3-6 AM, and temperatures should quickly cool down at the surface while slightly cooling down at 850mb as a result of the heavier precipitation, allowing for frozen precipitation to fall in the northern half of the area. Although the 925mb and 850mb layers are below freezing, there is a small warm layer above 850mb, meaning that sleet will also be involved in the forecast for most places that see frozen precipitation as the snow partially melts while moving through the warm layer and refreezes as sleet closer to the surface. At this time, I am thinking that the northwestern parts of the area towards extreme NW NJ to interior SE NY, and interior southern Connecticut will have at least a brief period of a moderate-heavy burst of snow and sleet tonight, with the heaviest precipitation likely towards northern Orange county into interior Connecticut, where the heavier precipitation may fall as mostly, if not plain snow. Should the heavier precipitation fall as snow, the snow totals will be enhanced in those areas compared to other places further south where sleet will limit the total accumulations. Some sleet may mix in south of the areas mentioned above, although any sleet should be brief with no accumulations. Towards the morning hours, temperatures aloft will begin to warm while remaining steady in the mid to upper 30s across most of the area, with a changeover to rain for most places except for Orange county, which may see sleet and/or freezing rain last into the morning hours.

Snow/sleet amounts also cannot be predicted with high confidence, as the accumulations will depend on how much snow and sleet each area sees along with how far south/north the main band of precipitation ends up. Based on the scenario mentioned above, I am expecting a swath of 1 to 3 inches of snow and sleet to extend from extreme NW NJ and Orange County, NY to interior SE NY and interior Connecticut. Amounts may end up locally higher in interior southern/central Connecticut and parts of Orange County. There is still some uncertainty with the accumulations, and if this forecast does bust, this map would likely be too far south, with the actual result a bit north of the map with a less snowy outcome.

Going into tomorrow afternoon, most of the rain will end, with temperatures remaining steady or slightly rising into the upper 30s inland and the upper 30s to lower 40s across the rest of the area. As the cold front approaches, the secondary low will begin to develop to the south of the area, helping to enhance the precipitation as it approaches the area. Light to moderate showers, locally heavy, are expected to redevelop around 5-6 PM while reaching the area, with the light to moderate rain lasting through about 10-11 PM. By 12 AM, the rain should end across most of, if not all of the area, with dropping temperatures and clearing skies. Windy conditions are expected to develop behind the cold front; while the exact intensity of the wind is uncertain and depends on the development of the secondary low, with a tight pressure gradient setting up, it is possible that winds may gust near to above 40 mph across parts of, if not most of the area for a brief time late Friday evening. Occasional breezy conditions should last overnight, with winds gusting again up to 40 mph on Saturday.

With all of the uncertainty, this forecast is still not a high confidence one. As the northern half of the area is near the southern border of the rain/snow line, slight changes with the north/south location of the band will also change the forecast precipitation types and the snow/sleet amounts expected. It is possible that a slightly further north scenario verifies, in which case amounts would be slightly lowered and temperatures would be slightly raised. An update reviewing what happened with the storm overnight as well as the latest forecast for the evening showers and the wind intensity will be posted on Friday morning.


Longer Range Brief Overview:


Chilly temperatures will continue through Monday, with highs generally in the lower to mid 40s. A weak low pressure will move through the Northeast on Tuesday, but this low pressure has trended weak enough to the point where it barely brings in any cold air, and the next storm develops further north and moves east, bringing more rain and warmth for the area. As should be expected, there is still uncertainty, but at this time a rain event still appears more likely than a snowstorm for the late week.

Thursday, February 23, 2012

Feb 23, 2012 Noon Updates



11:00 PM: After analyzing the latest set up, there are even more changes to the forecast tonight... tonight's update should be posted by 11:40 PM to 12 AM, and depending on the latest data it is possible that I may need to issue a Snow Watch (3+ inches of snow) for southern Connecticut.


4:55 PM: Despite the storm only starting tonight, the models still have yet to agree on a single solution for the storm, with the latest NAM run complicating the forecast even more by forming a stronger nor'easter on Friday night, with moderate to locally heavy rain for the area and a major snowstorm for interior New England. Later this evening I will post a detailed analysis on the differences with the models along with the latest expectation, although for now there will be two updates, both posted by 5:45 PM:


5-Day Forecast: Forecast temperatures for Friday will be significantly lowered.
Weather Alerts: Wind Alert for the entire area, Light Snow Alert inland.

Feb 22, 2012: Warmth Continues Tomorrow


Forecast Highlights:


- Temperatures remain above 55 degrees tomorrow for most places
- Colder storm expected Friday; brief period of sleet inland?
- Gusty winds Friday night, gusts above 40 mph likely
- Chilly and dry weekend, warming up early next week


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With a warmer air mass moving into the region, today ended up with warmer temperatures than those of yesterday, with partly to mostly cloudy skies and highs peaking in the mid 50s for most of the area along with some places reaching 57-58 degrees in the immediate NYC area.The latest radar to the left shows widespread showers to the southwest and northwest of the area. Most of the precipitation tonight will stay to the north and south of the area, with moderate rain towards central New Jersey and moderate snow in places such as Vermont, although isolated showers are still expected.

Temperatures will stay mild through tomorrow, although the storm for Friday is trending colder, and is expected to start as a cold rain for most of the area, maybe even mixing with sleet in the northern parts of the area. Temperatures will cool down behind the cold front with strong winds likely, although temperatures will warm back up again by next week.


Thursday and Friday: Stormy, But Differences With Temperatures


Tomorrow will be another mostly cloudy day for the area; although isolated showers are possible, most of the area will be dry. Temperatures are expected to be similar to those of today along with a west/WNW wind expected, with temperatures reaching the mid 50s for most places and upper 50s near NYC. Despite the Friday storm only 2 days away, there is still some slight uncertainty due to minor differences with the models regarding the storm.


Storm Precipitation: Today's model guidance trended south, colder and slower with the storm, with the ECMWF solution, yesterday's bold outlier, significantly backing out of its strong, amplified solution, although the latest ECM run is still likely catching up to the rest of the model guidance and therefore was not used for tonight's forecast. Overall, the UKMET and CMC appear to best represent the latest trends with the expected set up with the NAM and GFS gradually trending colder, and for tonight's discussion I used a NAM/CMC combination as guidance for the forecast.

The precipitation is expected to move into the area around 1-2 AM on Thursday night, at which time temperatures are expected to be in the lower to mid 30s in the interior areas (NW NJ/Orange county in NY), upper 30s to lower 40s in the immediate NYC area and Long Island, and mid 30s in southern CT. The 925mb and 850mb layers are expected to be cold enough at the start of the storm to allow for widespread snow and sleet in the southern Northeast and southern New England, although the southernmost extent of frozen precipitation is slightly uncertain; the GFS keeps the entire area with rain, while the NAM and the earlier CMC run today showing light snow/sleet accumulations in NW NJ, SE NY and southern Connecticut. The latest NAM run may have been a little too far south with the snow, and due to a warm layer aloft, I added a mention of sleet in the 5-day forecast for interior NW NJ, SE NY and southern Connecticut at the onset of the storm. Any frozen precipitation is expected to be brief before changing over to rain by Friday morning, with little to no accumulations expected. Otherwise, rain will fall across the rest of the area, with the steadier light rain ending by at least 7-9 AM with isolated showers lasting through the evening hours.


Temperatures / Wind Outlook: The temperature forecast for Friday is currently the most uncertain aspect of the forecast. Temperatures are expected to be in the 30s to lower 40s for Thursday night with the onset of the storm, rising towards the afternoon. There are minor differences with the location of the low pressure on the models, but the area will end up near the boundary of the warm front, meaning that these minor differences have a larger impact on the forecast for the area. Should the warm front end up north of NYC, which the 18z GFS and NAM runs supported, temperatures would surge into the 60-65 degree range by Friday afternoon/evening, and with a tight pressure gradient developing, strong wind gusts in the 40-55 mph range would be possible in the late afternoon and evening hours, locally exceeding 50-55 mph at most. In this case, a wind alert would be issued for the entire area, with a possible High Wind Watch. Should the warm front end up south of NYC, however, as the CMC, UKMET and 0z NAM are showing, temperatures would remain in the 40s throughout most of the day, briefly rising into the mid 40s to lower 50s late Friday afternoon ahead of the cold front, with winds gusting up to 40 mph, locally 45-50 mph, by the evening hours.

Friday's temperature forecast is currently not a high confidence one, as minor changes in the position of the warm front and low pressure will mean either 60-65 degrees in NYC and strong wind gusts, or 50 degrees and moderate wind gusts. For tonight's forecast, I am expecting the warm front to reach NYC, resulting in temperatures reaching the upper 40s for most of the area, along with lower to mid 50s near NYC/western Long Island and upper 50s southwest of NYC. Gusty winds up to 40 mph, locally 45-50 mph, are expected to develop across the area as well on Friday evening. The temperature forecast is subject to minor changes, however. Tomorrow night's update will include more information on the temperatures for Friday along with potential wind alerts for the area.


***2/23 Morning Update: The models last night, instead of solving the differences with the temperature gradient, have made it even more pronounced; with temperatures trending warmer on the models, there is expected to be a very tight gradient setting up somewhere near or just south of the area where temperatures in a short distance jump from the 40s to the 60s, perhaps even nearly 70 degrees. At this time, I am thinking that the gradient sets up over NYC, with temperatures in the upper 40s to low 50s north of NYC, mid to upper 50s near NYC and Long Island, possibly near 60 degrees, with temperatures reaching the 60s to 70 degrees in central New Jersey. This gradient is still subject to minor changes, however, and tonight's update may either increase or decrease the expected high temperature for Friday. Regardless of the temperatures, at least a brief period of strong winds is expected on Friday evening, with winds likely gusting up to 40-50 mph across most of the area, perhaps gusting locally above 50 mph in isolated locations. Stay tuned for more information with tonight's update.***


Weekend - Next Week: Chilly, Briefly Warmer Early Week, Then Colder


Temperatures are expected to cool down during the weekend behind the cold front, with dry and mostly sunny conditions expected. Saturday will be slightly cooler with highs in the lower 40s, with breezy winds still possible, with Sunday slightly warming up into the mid 40s for most places. A low pressure will move into the Northeast by Monday night into Tuesday, but is not expected to be strong, with the result increased cloud cover for the area, a risk of isolated showers, and temperatures warming up well into the 40s and possibly the lower 50s. Temperatures will slightly cool down into the 40s again by Wednesday with dry conditions.

The attention then turns towards late next week, when the next storm potential exists. The models are each showing a different outcome, as should be expected nearly a week away; today's GFS runs have generally showed a strong storm moving through the region, with warm temperatures and heavy rain for the area and a significant snowstorm for parts of New England. The 12z ECM went extreme with a major snowstorm for the area, the CMC had nothing, and the NOGAPS had a suppressed coastal low. This is too far out to make any solid forecast for the storm, but the set up is still unfavorable for a snow event, with a transient weak western ridge and no blocking in the Atlantic. With these variables missing, a near ideal set up would be required for the area to see snow; one small factor goes wrong and the storm will easily end up as either rain or nothing, and at this time both of these scenarios are more likely than a snowstorm. Stay tuned for more information on this time frame as details become clearer.

Wednesday, February 22, 2012

Feb 21, 2012: Rain, Warmer Ending To Week


Forecast Highlights:


- Warmer temperatures return; 50-60 degrees Wed-Fri
- Mostly cloudy, occasional showers tonight through Friday
- Dry, chilly next weekend again
- Temperatures gradually warm up next week


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After the southern Mid Atlantic snowstorm on Saturday, temperatures over the last two days have been chilly, although still warmer than average, peaking in the mid to upper 40s across the area today along with increasing cloud cover. The latest radar, posted to the left, shows scattered showers covering parts of the region; these showers are the start of a period of mainly cloudy skies, mild temperatures and occasional showers that will last through Friday night when a cold front moves through, with temperatures exceeding 50 degrees over the next 3 days. Colder and dry conditions will return by the weekend, although a gradual warming trend is likely around the start of next week.


Tomorrow's Outlook:


Mostly cloudy skies are expected tomorrow across the area. An isolated shower may be possible, although the best risk of rain is during the overnight hours. Temperatures will be noticeably warmer along with a southwest wind, peaking in the mid 50s across most of the area and the upper 50s in parts of the immediate NYC area.


Thursday - Friday: Still Mild, Wet


Storm Set-Up: The models have been showing many different solutions for the Friday storm despite it only being 3 days away, and the models today have only increased their differences. The ECMWF is the most extreme solution as a result of full phasing between the northern and southern streams, supporting a strong storm with heavy rain, possibly over an inch, temperatures surging into the lower 60s, and very strong wind gusts for Saturday. Meanwhile, the GFS does not have any interaction between the southern shortwave and the northern stream, resulting in a relatively weak storm moving through the Northeast with little rain for the area and no strong wind gusts. The latest NAM and GFS runs, however, trended slightly more amplified, and although the UKMET backed down today from its earlier runs supporting the ECM, the ECM remains consistent with a strong storm scenario.

Forecast for area: The ECMWF right now appears to be too amplified given the progressive pattern which doesn't favor full phasing and much more amplified solutions, although at the same time the GFS and NAM could be a bit too flat with the storm, as there is still some uncertainty with how far south the northern stream digs along with the timing of the southern shortwave. As a result, I am leaning towards a scenario where the cold front comes through on Friday night, with occasional light to moderate rain at times on Friday, mild temperatures, and gusts up to 30 mph, maybe 35-40 mph at most.

Temperatures on Thursday will be slightly cooler as the warmth is pushed south behind Wednesday night's weak rain event, with highs reaching the lower to mid 50s north/west of NYC, and the mid to upper 50s for NYC and further south. Friday's temperatures are a little uncertain due to some uncertainty with the timing and intensity of the storm, although there is enough confidence for temperatures to at least reach the mid to upper 50s, possibly the lower 60s near NYC in the warmer case scenario. Stay tuned for another update on this storm tomorrow.


Weekend And Beyond: Chilly, Dry


Colder temperatures will return behind the front for the weekend, with temperatures expected to peak in the mid to upper 40s on Saturday along with partly sunny skies and breezy winds. Sunday will be slightly cooler with mostly sunny skies and highs in the upper 30s to lower 40s, and Monday is expected to begin trending slightly warmer. The next low pressure will move towards the northern Northeast, bringing warmer temperatures for Monday night into Tuesday along with some rain, although no significant rain is expected, and cooler temperatures will return again by the middle of next week. The latest GFS runs have consistently attempted to show a snowstorm by the end of next week; the pattern, however, is still unfavorable, as I will discuss in my March outlook which will be posted on Friday, and either some rain or no storm is favored over a snow solution. Stay tuned for more information on the longer range.

Tuesday, February 21, 2012

Feb 20, 2012 Brief Update


Through Wednesday, the forecast has not changed for the area, with temperatures still expected to reach the mid 40s to lower 50s tomorrow and the mid 50s on Wednesday, locally in the upper 50s near NYC. The latest models, however, are showing noticeably different solutions for the late week and early weekend time frame, which are trending away from the very warm scenario and towards a not-so-warm and mostly dry ending to the week. As this is a new trend, there is some uncertainty, and I will post an updated forecast on Tuesday in the late morning, although for now I slightly lowered temperatures in the 5-Day Forecast page to accompany the potential trend towards colder temperatures.

Monday, February 20, 2012

Feb 19, 2012: 60+ Degrees Late Next Week?


Forecast Highlights:


- Chilly, dry start to week
- Warmer later next week, 60+ degrees possible
- Rain returns for Tuesday through early Saturday


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A suppressed storm affected the Mid Atlantic today, bringing widespread accumulating snow as far south as southern Virginia and northern North Carolina, with reports as high as 8-10 inches in the higher elevations. With the storm staying well to the south of the area, mostly to partly sunny skies were observed today with high temperatures reaching the mid 40s across the area.

Briefly cooler temperatures will stick around through Monday, although a ridge will build into the region again by the middle of next week. As a few storms move through the region, more clouds and rain are expected for the second half of the week, and at least one day may reach 60 degrees.


Week Overview:


Monday will be the coolest day of the week. With a high pressure in place, mostly sunny skies are expected along with highs in the lower to mid 40s across the area. Temperatures will slightly warm up on Tuesday as the cold moves out, with highs reaching the mid to upper 40s inland and the upper 40s to lower 50s across the rest of the area.

The forecast becomes more complicated for the second half of next week as several low pressures move to the northwest of the area, but the overall theme for this time frame is mild, mostly cloudy and rainy. Wednesday will likely feature mostly cloudy skies with a risk of showers in the morning, with temperatures peaking in the lower to mid 50s inland and the mid to upper 50s across the rest of the area. Thursday's temperatures are uncertain depending on the location of the next low pressure; although for now, I went with temperatures similar to those of Wednesday, should the storm end up further north, temperatures on Thursday may get close to 60 degrees.

The biggest uncertainty right now is with Friday's forecast, as the models develop a strong storm well to the northwest of the area, which makes more sense than a suppressed storm due to a large ridge likely in place prior to the storm. With the trough axis near the central US, the possibility is there for a medium or strong intensity storm to form to the west of the area on Friday into Friday night, which would result in rain and warm temperatures. How warm temperatures get will depend on the location of the storm and the warm front, but temperatures in the 50s are expected again, and should the area be in the warm sector of the storm, temperatures could easily reach and pass 60 degrees. The cold front is likely to move through overnight, with a dry weekend likely to set up. Stay tuned for more information on the outlook for late next week.

Saturday, February 18, 2012

Feb 18, 2012: Mild Week Coming Up


Forecast Highlights:


- Chilly weekend, snow stays south tomorrow
- Warmth returns, 50+ degrees by middle of next week
- Second half of week to become mainly cloudy, rainy


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After a partly sunny start to the day, cloud cover increased with cloudy skies by the afternoon hours. Light rain associated with a weak low pressure moved through the area over the last few hours, with the cloud cover expected to clear tonight into tomorrow. This light rain event, as explained in more detail in the next section, is the main reason why tomorrow's storm will stay south of the area, bringing some snow to Virginia while the area sees partly sunny skies with highs in the 40s. Temperatures will stay chilly through Monday before warming up by the middle of next week again, with widespread 50s likely especially on Wednesday, along with the next chance of rain.


Tomorrow's Outlook: No Storm For Most Of Region


Tomorrow's Mid Atlantic storm was difficult to forecast from the medium range; the models did not handle the northern stream and the southern US shortwave well, resulting in a variety of different solutions ranging from a strong storm on the GFS with a heavy snowstorm for the area, to the suppressed CMC which at one point did not bring precipitation north of North Carolina. The pattern, however, is still progressive, which supported evidence that the strong storm on the GFS was an outlier solution and that a suppressed storm was more likely. The models seemingly settled on a close to final solution yesterday which would bring moderate snow to Virginia and light snow to Washington DC, although a last minute trend is unfolding as the low pressure near Louisiana is developing differently than modeled earlier today. The latest models show a double low pressure in the northern Gulf of Mexico instead of a consolidated, slightly stronger low pressure near western Louisiana, as a second low pressure also developed near an area of stronger convection in western Florida which is supported by the latest observations. As a result, it is becoming apparent that at this rate, the northern forecasts for the storm may fail, with very little precipitation in Washington DC, if any even falls there, and less snow than expected in Virginia.

For the NYC area, with the storm staying to the south, mostly to partly sunny skies are expected tomorrow, with temperatures in the lower to mid 40s across the area. A light north wind is expected.


Next Week Overview: Warmer, Becoming Cloudy/Rainy


Monday will be a chilly day again, with high temperatures expected to peak in the lower to mid 40s along with mostly sunny skies. Tuesday will be slightly warmer with a little more cloud cover as the cold air mass retreats, with temperatures warming up, reaching the mid to upper 40s inland (NW NJ and interior SE NY) and the upper 40s to lower 50s across the rest of the area. While these temperatures are still warmer than average, the temperature departures are not as high as they were earlier in the season when average temperatures were lower than they are now.

Between Tuesday night and Friday, several weak storms will move through the region, bringing occasional periods of light rain to the region while making for a more complicated forecast. The first wave of rain will move through around Tuesday night into Wednesday, with scattered showers likely at this time. Wednesday is currently likely to be the warmest day as long as there is little rain during the day along with breaks in the cloud cover, with temperatures likely to reach the upper 40s to lower 50s, even getting close to 55 degrees near NYC. This assumes that partly to mostly cloudy skies will take place; should cloudy skies and/or more showers than expected take place, high temperatures will be lower. Most of the models are showing another storm potential around Thursday, and while the development of this storm is still uncertain, ranging from a moderate rain storm on the GFS to almost nothing on the ECMWF model, at least some rain is likely to fall, with moderate rain amounts a possibility. Temperatures are likely to end up near the upper 40s, although should the wetter scenario verify, temperatures will be slightly cooler than currently expected. Some models attempt to pop up another storm after Thursday, although at this time, indications are that should another storm develop, it would likely do so around Friday and/or parts of Saturday, with a drier second half of the weekend possible, or an entirely dry weekend should the second storm fail to develop. Stay tuned for more information on the outlook for late next week.

Friday, February 17, 2012

Feb 17, 2012 Evening Note

Due to technical difficulties with my computer, tonight's update has been delayed to Saturday morning. There are no changes in the forecast through Tuesday, with the weekend storm still expected to stay well to the south of the area, with the only chance of precipitation on Saturday night in the form of flurries to the north of NYC and perhaps a brief drizzle in NYC.

Thursday, February 16, 2012

Feb 16, 2012 Brief Update


Forecast Overview:


- Tomorrow and Saturday will both be warmer than average. Mostly sunny skies are expected with highs in the mid 40s to lower 50s.

- By Saturday night, the northern stream will end up too fast to phase with the southern shortwave, completely ruling out a strong storm scenario like yesterday's GFS runs. With this difference, light snow will move through the Northeast on Saturday night, and while most of the light snow will stay to the north of the area, I added a risk of flurries in the forecast for Saturday night.

- The trend away from a phase is leaving the suppressed solution, mentioned last night as the likely solution, as the main scenario for the storm, with most of the moderate snow staying south of Maryland to southern NJ. The models will still continue to shift slightly south or north, and at this time I am still expecting most of, if not all of the snow to stay south of NYC. Despite this, a few snow showers could reach the area should the storm trend north. Stay tuned for a detailed discussion on the storm on Friday night.

- Behind the storm, windy conditions will develop for Sunday night into Monday, with lows in the upper 10s to upper 20s and highs in the mid 30s to lower 40s. Temperatures will gradually warm up well into the 40s and possibly the lower 50s by the middle of next week, with rain possible for that time frame as well.

Wednesday, February 15, 2012

Feb 15, 2012: Watching This Upcoming Weekend


Forecast Highlights:


- Light rain returns again tomorrow
- Warmer again, near 50 degrees Friday/Saturday
- Weekend uncertainty - big storm potential exists


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Cloudy skies were observed across most of the area yesterday and today as a weak storm moved through the region, which produced more widespread rain showers than originally expected, covering the majority of the area. Temperatures were in the mid to upper 40s across the area today, still slightly warmer than average. Temperatures will generally stay in the mid 40s to lower 50s through Saturday, although uncertainty significantly increases by the weekend, when a storm potential exists for parts of the region, possibly including the area.


Thursday - Saturday Outlook: Mild, Rainy Tomorrow


Another weak but slightly more organized low pressure will move into the region tomorrow, bringing widespread rain with temperatures peaking in the lower to mid 40s across the area. Isolated flurries may be possible inland by the end of the storm, but no snow accumulation is expected. Friday and Saturday will both bring mostly to partly sunny skies with high temperatures reaching the mid to upper 40s inland and the upper 40s to lower 50s across the rest of the area.


Sunday Uncertainty: Big Storm Or Nothing?


It has been apparent that a storm would be likely to affect parts of the East Coast this weekend since the last update two days ago. Since then, however, uncertainty has significantly increased, with some models showing a big rainstorm for the area and heavy snow in the interior Northeast, and others keeping the storm even south of North Carolina. While there is too much uncertainty to make any high confidence forecast, there are some hints on the model guidance regarding the potential scenarios for this storm.


Set-Up For Storm: Up until this point, most of the storm potentials for the area were either expected to produce rain or stay offshore, with the storms containing the snow potentials likely to be weak. This time, however, there are several key parts to the set up that make it more supportive of an East Coast storm than the previous potentials. The most significant difference is a low pressure near Newfoundland with weak ridging near the Davis Strait. This low pressure position, known as a 50/50 low for its position at 50N, 50W, is often found during winter storms in the Mid Atlantic and Northeast. In addition, the southern shortwave in the southern US is much stronger and more moist than most of the others so far this winter, meaning that should phasing take place, the potential would be there for a big storm to develop containing heavy precipitation.

The main issue with this set up is the lack of a strong, established western ridge to result in more amplification, and the generally progressive flow. In addition, storms this winter have had trouble phasing at the right location for the I-95 corridor to see a big snowstorm, and as will be discussed below in more details, the GFS shows a nearly ideal scenario for parts of the area to see a snowstorm. The main question right now is regarding the location and timing of the northern and southern streams, and where phasing takes place, if any and if so then how much. Should less phasing take place, the progressive flow would prevent the storm from moving up the coast, with the result a wet yet mild storm moving ENE in the southern, possibly central Mid Atlantic producing rain and some snow but no big snowstorm. If phasing does take place, however, then a stronger storm would be able to move up the coast and produce heavy snow and rain for the region.


Model Overview: The model guidance over the last two days has been variable with the storm, especially with today's models. The southernmost models today were the ECMWF and the 12z CMC. The ECMWF, which 2 nights ago showed a big snowstorm for the Mid Atlantic and a moderate storm for parts of the area, has stayed far to the south of the area with the storm today, with precipitation barely making it north of North Carolina. Last night's 0z CMC run showed snow making it up to southern NJ, although the 12z run significantly shifted south, keeping the storm entirely in the Southeast. The northern models are currently the GFS and the UKMET; the UKMET shifted north with its 12z run to show a scenario close to a big snowstorm for parts of the area, with the GFS the most extreme with such a solution. Although the 6z GFS run was further south, the 0z and 12z runs had a significant snowstorm with over 10 inches north and west of NYC, while the 18z run was wetter and warmer, with heavy rain in the immediate NYC area and heavy snow in the interior Northeast. The NAM is slowly trending north, but for now remains in between the northern and the southern solutions.


To the left, I posted an image from the 12z GFS run from the NCEP model page (direct link to 12z GFS). This image shows a heavy wet snow further north/west of NYC, with heavy rain in NYC and further south/east. This is the result of a phasing solution where the storm phases at the ideal location for the area to see snow; with the uncertainty regarding the set up, the phase has to be nearly ideal for the area to see snow, as any slight shifts would either turn this into a big rainstorm or keep the storm to the south of the area. In contrast to this run, the 12z CMC keeps precipitation entirely to the south of the North Carolina/Virginia border. Timing differences are also clear with the models, as at the same time that the 12z GFS has the storm emerging off the Mid Atlantic coast, the CMC only has the storm near New Orleans. The latest 0z GFS run may serve as proof that the 12z and 18z GFS runs were outliers, as the run still phases the storm but has it further southeast.


Latest Thoughts On Storm: As shown with the models and the storm set up, there is too much uncertainty right now to make any high confidence forecast regarding this storm. However, while the GFS is likely too extreme with this storm, at least a slight north trend is possible with the southern models. For now, I am going with a slightly further north scenario than the southern models, with at least a 30-40 percent chance of light rain or snow for Sunday. The bigger risk with this set up is for the storm to miss the area to the south, instead producing rain and some snow in the southern and central Mid Atlantic, but the less likely but still possible scenario is where more phasing takes place, with a big storm producing either rain/snow or heavy snow for the area. The latter solution does not have as much support and for now the first solution of a more suppressed low is favored, but will be watched in case it becomes more likely. Stay tuned for more information on the weekend outlook with tomorrow's update.

Feb 15, 2012 Noon


6:00 PM: Over the last day, there have been noticeable developments with the storm potential over the weekend. A detailed discussion on this weekend's outlook, along with a quick overview of tomorrow's storm, will be posted with tonight's update. An updated 5-Day Forecast will also be posted later this evening.

Monday, February 13, 2012

Feb 13, 2012: Rain On Thursday; Still Mild


Forecast Highlights:


- Warmer week ahead; 50+ degrees Wednesday
- Rain returns for Thursday afternoon/evening
- Chilly and dry weekend; snowstorm likely to stay south


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With a high pressure moving into the region, today brought drier conditions along with mostly sunny skies. Temperatures were chilly today but still at least 2-4 degrees warmer than average, peaking in the mid 40s across the area. The radar posted to the left shows that isolated light precipitation is moving into West Virginia; this precipitation is associated with a widespread yet weak and dry system that will move into the area tomorrow, bringing mainly cloudy skies along with an isolated rain or snow shower at times, especially in the evening and overnight hours.

Temperatures once again will stay warmer than average through the week, reaching the 50s in most of the area on Wednesday and possibly in some places again on Friday. The next storm will move into the area on Thursday, and while there may be a bit of cold air initially to result in a brief period of snow/sleet inland, rain will be the primary precipitation type. Chilly temperatures will return again for the weekend, although the next snow potential once again appears likely to focus to the south of the area.


Tomorrow's Outlook:


With the weak storm moving into the region, clouds will increase tonight, and mostly cloudy skies are expected tomorrow transitioning to cloudy skies by the afternoon. Temperatures will be slightly warmer than those of today, reaching the lower to mid 40s inland and the mid 40s across the rest of the area, along with a SSW wind expected. Isolated rain/snow showers are possible, especially in the evening and overnight hours, but no snow accumulation is expected.


Wednesday - Friday: Mild, Rainy At Times


The storm will mostly move out by Wednesday, although isolated rain/snow showers are still possible in the morning. Partly cloudy skies are expected by the late afternoon with warmer temperatures, reaching the upper 40s to lower 50s across the area. In the warmer case scenario, temperatures may approach 53-55 degrees close to NYC.

By Thursday, the next storm will approach the region, although this storm will be stronger than tomorrow's weak event. The latest trend on the models has been towards more suppression of the storm, with the primary low staying in the Ohio Valley instead of moving way north into the Great Lakes. A transfer to a secondary low pressure further southeast will take place with this set up, and the transfer is becoming more likely to take place further south. The latest NAM run has most of the precipitation falling with temperatures at 850mb below freezing, although this does not signal a snow event in this case; 925mb temperatures closer to the surface are very marginal, only near freezing in NYC and slightly below freezing inland, and surface temperatures are still in the 40s in NYC and in the 30s inland. As a result, I kept the precipitation type as rain for the immediate NYC area (NYC and its north/west suburbs) and further east, while adding a risk of snow and sleet around noon on Thursday. In the colder case scenario, the storm may start out with a brief period of snow and/or sleet all the way down to the immediate north/west suburbs of NYC. The rain will otherwise intensify by the afternoon and evening hours, ending towards midnight with at least 1/4 to 1/2 inch of rain expected. Partly sunny skies will return by Friday with breezy conditions possible and temperatures peaking in the mid to upper 40s across the area.


Next Weekend: Chilly; Storm Likely To Stay South


As mentioned since late January, the recent western US ridge signaled that the pattern across North America has changed. The polar vortex has been displaced over southeastern Canada for the longest time so far this winter, and once it retreats back north over the next couple of days, it is expected to stay out of Greenland and Alaska, where it has been stuck over the last couple of months resulting in a mild pattern with very little snow for the region. Although the recent pattern change still favors warmer than average temperatures and not many snow chances, there are some minor changes that slightly increase the potential for a snow event for parts of the region around next weekend. The late week storm will move towards Newfoundland, but will be unable to move quickly into Greenland as weak ridging will develop west of Greenland, a factor that is often observed during snowstorms south of the Northeast. With the trough in place, there is also likely to be an initial cold air mass in place. The main issue at this time is the western US, as little ridging is expected, making the set up less amplified and any storm more likely to move offshore rather than straight up the coast. Most of today's models reflected this with a rain/snow event for North Carolina and the southern Mid Atlantic, although the 18z GFS run took the storm further north, with light rain/snow in parts of the Northeast. There is still a lot of uncertainty with this set up, but at least at this time it is likely that the weekend storm should stay to the south of the area, with otherwise chilly temperatures along with low temperatures in the 20s and highs in the 30s. Temperatures are expected to warm up again by early next week back into the 40s. Stay tuned for more information on the outlook for next weekend.




Sunday, February 12, 2012

Feb 12, 2012: Warmer Again This Week


Yesterday's storm, although having the potential to bring at least 1 inch of snow to most of the area, ended up busting on the low side as the coastal low formed too far offshore. As a result, the area saw anywhere from a coating of snow to close to an inch. The storm overperformed in terms of snow totals further south, towards the central Mid Atlantic, where an inverted trough brought moderate snow in the evening hours, increasing snow totals more than expected. Much colder temperatures were observed today, peaking in the lower 30s across most of the area, along with scattered snow squalls which brought a coating of snow to places such as Rockland county in NY, parts of NYC and western Long Island. Temperatures will warm back up this week, although no significant rain event is in the forecast within the 7 day range.


Week And Weekend Overview:


Tomorrow will bring mostly sunny skies to the area with temperatures returning back to where they have been during almost the entire winter, warmer than average, with high temperatures reaching the upper 30s to lower 40s across the area.

Temperatures will slightly warm up on Tuesday, with scattered rain/snow showers during the day and in the overnight hours, but will warm up more noticeably into the mid to upper 40s by Wednesday and Thursday. A storm will move into the region on Thursday, bringing widespread rain showers across the area into the overnight hours. Friday is likely to be drier with slightly warmer temperatures, once again reaching the mid to upper 40s, possibly getting close to 50 degrees in the immediate NYC area. A trough will move into the region behind Thursday's storm, bringing colder temperatures for next weekend, ending up closer to average with lows in the 20s and highs in the 30s. Temperatures are expected to warm up towards the start of next week again along with the next possibility of a storm.

Feb 12, 2012 Noon: Snow Showers


5:05 PM: Scattered Snow Squalls


Behind yesterday's light snow event, scattered snow showers are currently affecting parts of the area. A light to locally moderate snow squall is located near southeastern New York, focusing over Rockland county, spreading towards northeastern NJ and Westchester county. This squall will continue to move SE to ESE, moving towards central and western Long Island and northern areas of NYC within the next 1/2 to 1 hour. Gusty winds along with a possible dusting of snow are expected with these squalls.

The next forecast update will be posted this evening.

Saturday, February 11, 2012

Feb 11, 2012 Storm Updates


Below, updates will be posted on the light snow event currently affecting the area.

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9:50 AM: Light Snow Still Falling


The area is mostly seeing light snow falling, but with temperatures very marginal at the surface, the snow is having a very hard time accumulating, and is even melting in some places despite a steady light snow. A slightly heavier band of light snow is currently near the immediate NYC area, but this band will slowly shift east while slowly intensifying as the low pressure, currently east of the North Carolina/Virginia border and moving northeast/ENE, continues to intensify. The snow will likely end for most places north and west of NYC by 11 AM, with the snow sticking around in the eastern parts of the area through early this afternoon. Accumulations across almost the entire area will remain below 1 inch, with amounts locally slightly higher than 1 inch possible in isolated areas.

There is additional precipitation currently near western Pennsylvania, but this part of the storm will not reach the area. An inverted trough will move to our south later tonight, bringing light to moderate snow across central PA into south/central New Jersey and the rest of the Mid Atlantic, although only isolated snow showers are expected in the area. Temperatures tonight will drop into the mid 10s to lower 20s across most of the area with mid 20s in NYC along with gusty winds developing, gusting up to 30-40 mph late tonight across at least parts of the area. Windy conditions are expected again tomorrow, gusting up to 30-40 mph again, along with scattered snow showers especially in the afternoon hours.

Friday, February 10, 2012

Feb 10, 2012: Light Rain/Snow Tonight


Cloud cover gradually increased across the area today with temperatures peaking in the 40s. With an approaching storm, cloud cover has increased today with cloudy skies currently observed across the area. Although the expectation is for some light snow to fall out of this, the latest observations signal that despite yesterday's scaled down forecast, there could be even less snow than expected out of this storm.


Tonight - Tomorrow: Generally Up To 1", Locally 2-3"


Last night's update mentioned that one of the uncertainties with the storm was regarding whether it would develop closer to the coast or further offshore, with the offshore scenario the more likely solution. Today's model guidance settled on the offshore scenario, with the low pressure expected to develop well offshore. There is already light precipitation across the region, falling as snow away from the coast and light rain closer to the coast, although temperatures will gradually cool down tonight, allowing for a changeover to light snow in NYC by at least 1-2 AM and further southeast after 2 AM. By that time, widespread light snow will fall from NYC and north/west, but will have trouble sticking and accumulating due to the marginal surface temperatures, still in the lower 30s away from NYC and the mid 30s closer to NYC.

The development of the coastal low will take place too far offshore for the region to get any large precipitation amounts, and as a result, only light precipitation is expected to affect the area through tomorrow afternoon. Light snow, mixing with rain at times in Long Island, will continue to fall through at least 12 PM, with the snow in southern Connecticut and eastern Long Island sticking around a little longer. During the whole event, it will be difficult for the snow to accumulate due to marginal temperatures, and as a result, accumulations will likely be lower than the average 10:1 snow to liquid ratio.


Forecast For Area: Overall, the final storm forecast has been downgraded from yesterday's update, with up to 1 inch of snow expected north and west of NYC and in NYC itself, locally up to 2 inches especially north and NE of NYC. Long Island will likely see up to an inch, with northern parts of Long Island potentially getting closer to 1.5 or 2 inches, with southern Connecticut, especially further east, seeing at least 1 to 3 inches of snow. With the lowered accumulations, I removed the Light Snow Alert for the entire area except for southeastern CT, which has the best chance of seeing 2-3 inches of snow across the area.

To the left, I posted a snow map for this storm. Due to the uncertainty, this snow map only has medium confidence, and parts of the map are still uncertain. Although NYC is within the 1-2 inch range on the map, lower accumulations are expected, and I placed text to show accumulations near 1 inch in the NYC area, locally lower or higher, although accumulations in NYC itself at this time are more likely to end up below 1 inch. The biggest uncertainty with the map is regarding the accumulations in the immediate NYC area, as well as accumulations in Long Island, where uncertainty with the rain/snow line may make the difference between a coating of snow and accumulations near 2 inches. Stay tuned for storm updates tomorrow morning.


Longer Range: Cold temperatures will briefly return for this weekend, with high temperatures reaching the upper 20s to lower 30s across most of the area on Sunday along with windy conditions and partly sunny skies. Temperatures will warm back up into the 40s for next week, excluding Monday which will likely bring temperatures into the upper 30s, although a weak low pressure will move through the region on Tuesday into Tuesday night, bringing a risk of isolated snow showers across the area. Another storm may be possible towards the end of next week into next weekend, although at this time the probability of a significant storm appears low. Stay tuned for more information on the longer range.

Thursday, February 9, 2012

Feb 9, 2012: Light Snow For Saturday


With yesterday's storm clearing the region after producing up to 1/2 inch of snow, locally higher, across parts of the area, today brought mostly sunny skies with high temperatures rising back into the 40s, melting the leftover snow from last night. Temperatures will stay mild through tomorrow, reaching the mid to upper 40s across most of the area, but the biggest development in the forecast is for a light snow event on Saturday which will likely end up as one of the only snowstorms of the winter to produce over 1 inch of snow for the area.


Friday Night - Weekend: Light Snow, Then Cold


Yesterday's update mentioned how a storm will affect the area on Saturday with light snow, but since the last update, this afternoon's models trended further west and stronger, with the NAM and SREF showing the potential for nearly 5 inches of snow in NYC and more significant amounts northeast of NYC. The models backed away further southeast this evening, however, with the 18z GFS again showing a light snow event, although the NAM still showed at least 3-5 inches of snow north and northeast of NYC. The latest 0z GFS run complicated the situation even more, suddenly trending towards a solution close to what the NAM had earlier today with a stronger and snowier storm.


The models are still having issues with handling the storm even though it's less than 2 days away, which is resulting in lower than average confidence in the forecast. Although huge changes will not take place with the storm, minor changes are still causing uncertainty with the forecast, especially regarding where the main low pressure develops. To the left, I posted an image from the 00z NAM from the NCEP model website (direct link to 0z NAM), showing two low pressures; one is due east of the North Carolina and Virginia border, and the second low pressure is southeast of the first one, directly over the heavy precipitation marked with blue and purple colors. The question is which low pressure becomes the dominant one; the latest GFS run and the NAM runs which showed a bigger snowstorm focused on developing the western low pressure, which then moved up the coast to bring moderate snow accumulations to the I-95 corridor. The CMC and UKMET, along with the 0z NAM which is posted above, develop the further east low pressure, resulting in light rain/snow for the area with at least 1 to 4 inches of snow north and northeast of NYC, but the main storm stays offshore, preventing the entire region from seeing moderate to heavy snow accumulations.

Although there are still about 36 hours left until the strongest part of the storm affects the area, slight changes are still expected with the models. There are two main possibilities for the storm at this time; one is where light snow affect places north, NE and west of NYC, with light rain/snow in NYC and Long Island, with accumulations between 1 and 3 inches, locally higher in southern CT. The second scenario is where a stronger storm develops, bringing at least 2 to 5 inches of snow in the immediate NYC area with 3 to 6 inches towards southern Connecticut and northeast of there. For now, I am going in between, leaning a bit towards the less snowy solution due to lower than average confidence, but the potential is there for a snowier outcome than currently expected.

Despite the uncertainty with the overall set up, snow will still fall across the area. Light snow is expected to develop after at least 12 AM with the storm ending around noon Saturday. The intensity of the precipitation is the main uncertainty, and should the storm end up weaker, more rain would fall in Long Island and NYC, with lower snow accumulations and warmer temperatures, reaching the upper 30s to lower 40s, while a stronger storm would bring more snow than rain to these areas while keeping temperatures lower. The storm will end by the early afternoon hours, with isolated snow showers lasting overnight along with windy conditions developing, with gusts up to 40 mph possible resulting in wind chills dropping into the single digits by Sunday morning for parts of, if not most of the area. Stay tuned for more information on the storm, the weekend cold and any updates that may change the forecast.


Next Week Overview: Temperatures will stay chilly through Monday and Tuesday, although the latest models are signaling that another light snow event may be possible around Tuesday night into Wednesday. Should this potential verify, it will not be a big storm but rather a light snow event similar to yesterday's storm.

Wednesday, February 8, 2012

Feb 8, 2012: Winter Finally Arrives, For Now


Forecast Highlights:


- Storm potential for weekend increases; widespread light snow likely
- Cold temperatures this weekend, highs struggle to reach 30 on Sunday
- Warmer next week, but not very warm


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As this afternoon's update noted, a light snow event affected the Mid Atlantic including the area today, with widespread 1-2 inch amounts in parts of Pennsylvania. This evening, a weak area of light snow not detected very well by the radar affected the area, bringing a dusting to most places with totals up to 1/2 inch towards southern Long Island, NYC and towards central New Jersey. The radar to the left shows that most of the snow has moved out, but occasional flurries are still falling in Long Island.

Today's snow event marks the first snow event as a result of the temporary pattern change, which will finally bring a period of more winter-like conditions to the area through at least next week. The peak of this wintry-like time frame will be in the weekend, when a light snow event will affect the area followed by colder temperatures for the weekend. Although temperatures will warm up again next week, the pattern will fail to return exactly to where it has been until now.


Thursday - Friday: Warmer, Snow Quickly Melts


Temperatures will quickly warm back up tomorrow behind the snow event, with temperatures reaching the lower to mid 40s across the area along with mostly sunny skies and light winds, melting any leftover snow from today. Temperatures will slightly warm up again on Friday with partly sunny skies along with temperatures reaching the mid to upper 40s across the area.


Weekend: Colder, Light Snow Expected


With the temporary pattern change including stronger ridging in Alaska, there have been indications over the last 10 days that the best potential for a snow event could be around this time frame. This potential is now looking more likely, with the latest model guidance trending towards a coastal storm developing slightly closer to the coast. Regardless of the coastal low, a cold front will move through the region on Friday, bringing widespread snow showers to the region, including the area, along with highs in the mid to upper 30s for most of the area. The uncertainty comes in regarding any coastal low, as the GFS and NAM have been trending west and stronger with this feature, bringing light rain/snow changing over to snow for NYC for Friday night into Saturday morning. Surface temperatures are marginal for this event with the latest models as the storm is mostly offshore, resulting in light rain/snow with light accumulations at most. However, there is still some uncertainty with this time frame, and one of the possibilities is that the low pressure trends slightly further west and stronger, which may result in a scenario supporting light accumulations for the area above an inch. Regardless, the probability of at least some light snow affecting the area on Saturday appears to be moderate to high at this time. Stay tuned for more information on the light snowstorm potential for Friday night into Saturday.

Behind this storm, some of the coldest temperatures of the winter will move into the region. Sunday will be the coldest day with partly sunny skies and windy conditions, with gusts possibly up to 40 mph. Depending on later model runs, a Wind Alert may be needed for the weekend. Temperatures will be much colder, only peaking in the mid 20s to lower 30s across the area, with overnight lows in the upper 0s to mid 10s for most places except for NYC, which will be slightly warmer. Along with the wind, wind chills may end up in the single digits for parts of, if not most of the area.

Temperatures are expected to warm back up into the 40s by next week, although no significant warm spell appears to be in the picture yet. Stay tuned for more information on the weekend cold as well as the outlook for next week with tomorrow's update.

Feb 8, 2012 Noon Update


A more detailed update will be posted later tonight, although for now I posted a short discussion focusing on the two light snow events. The 5-Day Forecast will also be updated tonight.

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Today / Tonight: Light Snow, Mostly South of NYC


The latest radar posted to the left shows that widespread light to moderate snow is affecting Pennsylvania and southern New Jersey. Earlier today the radar had the appearance that the snow was aiming straight at NYC, but a coastal low is currently developing off the coast of the Mid Atlantic, which is causing the snow in Pennsylvania to collapse with more precipitation developing closer to the coastal low, towards the eastern Mid Atlantic.

Some snow showers are still expected for the area, but the best risk of something more than flurries is from NYC and further south/east, with a dusting of snow possible. The steadier light snow with accumulations in the 1/4 to 1 inch range is expected to end up from central New Jersey and further south, although light accumulations up to 1/4 inch in the case that heavier precipitation spreads in from the southwest may be possible up to NYC.


Friday Night - Saturday Night: Widespread Snow Showers Likely


The time frame around next weekend, which is in the time frame which I mentioned since my January 27 update could include at least one snow event, is looking more likely to bring widespread snow showers for the region. The pattern has already temporarily changed as the polar vortex in Alaska has been displaced for a longer period of time and instead is displaced near the Hudson Bay, is allowing for slightly more sustained cold air to affect the region. With this temporary pattern change, the recent snow events so far have stayed south of the area surprisingly, as observed last weekend and again today, and while the weekend event is also likely to mostly stay offshore, more widespread precipitation is expected.

A large trough will drop from the Great Lakes into the region during the weekend, with the cold front likely to bring widespread snow showers and snow squalls, especially in the interior Northeast but in parts of the area as well. Along with the snow shower potential, a coastal low is likely to develop further offshore. Exactly how far offshore it develops is still uncertain, with solutions ranging from light rain/snow on the CMC to a steadier light snow with light accumulations on the ECMWF. The set up is unfavorable for a coastal storm to rapidly intensify right along the coast to provide a significant snow event for the area, although the potential is there that should the coastal low develop close enough to the coast and end up slightly stronger, a period of light snow for the area, mixing with light rain near and southeast of the I-95 corridor, may be possible, along with more snow for eastern New England. Stay tuned for more information on the weekend outlook with tonight's discussion.