URGENT UPDATE 9.28.12

Unfortunately, my computer has stopped working. Updates in the blog will be suspended for likely at least the next few days. Brief updates on the forecast and on the status of the blog will be posted on the NYC Area Twitter page for now.

9/30/12 - A preview of the October outlook has been posted in the Long Range page. The full outlook will be posted at some point this week.


**Tuesday, 10/2 Update: Blog updates will resume tomorrow (Wednesday, 10/3). The October outlook will be posted as well.**

Sept 28, 2012 Noon Update

Several mid-day observation and forecast updates:

1. Today's storm was faster moving than expected but also produced less rain than my outlook called for last night, which was on the conservative side of the model guidance, with most places north and west of NYC seeing up to or a little over 1/2 inch. The most significant impact from today's storm, however, came in NYC, northern Long Island and coastal Connecticut, where a severe thunderstorm developed producing strong wind gusts and flash flooding, with radar estimates showing 2-4 inches of rain in coastal areas. More information on today's observations will be posted with tonight's update.

2. A forecast change has taken place for next week's outlook, as latest indications point to a low pressure affecting the region on Tuesday with widespread rain. This is only a recent change, and more information on the outlook for next week will be posted tonight, including an update on the long range cool spell and some thoughts going forward into October.

Tonight's update will discuss the aforementioned topics in more detail.

Sept 27, 2012: Rainy, Then Warmer

Forecast Highlights:

- Rain, thunderstorms expected tomorrow; highs in upper 60s-low 70s
- Mostly cloudy, few showers for weekend, Monday
- Warm up towards middle of next week

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Tonight - Monday: Chilly, Rainy

The latest radar, posted to the left, shows the rain that will affect the region tonight into tomorrow located over Pennsylvania. The storm appears to be ahead of schedule, and is expected to clear most of the area by noon except for eastern areas, which will see some showers persisting beyond noon. The heaviest rain is expected to stay north of the area, with showers and thunderstorms expected to affect the area with the peak during the morning hours. Rain totals are expected to end up between 1/2 and 1 inch, locally up to 2 inches, north and west of NYC, with lower totals for Long Island. Temperatures will warm up into the upper 60s to low 70s across the area.

As the wave of low pressure moves out, mostly cloudy skies will continue for the weekend with a risk of scattered showers, especially east and NE of NYC, as an upper level low remains in place over the region. Temperatures are expected to reach the mid 60s to 70 degrees on Saturday and the upper 60s to low 70s on Sunday. Similar temperatures are expected again for Monday.


Tuesday - Beyond: Warming Up

The upper level low will gradually exit the region, with another wave of low pressure expected to stay south of the area on Tuesday. More sustained ridging will then build into the region for the first time since mid September, with temperatures quickly warming up across the region well into the 70s, likely peaking in the mid to upper 70s in the area during the peak of the warm spell. Uncertainty increases for the longer range as models differ with their handling of a dropping cold air mass in Canada; although there is expected to be ridging in the western Canada/NE Pacific region, it appears that the trough will extend towards the southwest US, which at least through the medium range should prevent an amplified trough from dropping into the region, rather favoring more of a gradual cool down with temperatures likely returning towards the 60s-low 70s range. With the pattern uncertainty there are model differences regarding the timing of the next cold front, although it appears that it may come through sometime late next week or next weekend with the possibility of rain. Stay tuned for more information on the longer range.

Sept 26, 2012: Rain, Chilly Temperatures Return

Forecast Highlights:

- Mostly cloudy skies to persist through Monday
- Chilly rain expected on Friday; sub-60 highs possible inland
- Showers possible Saturday through Monday
- Warm up expected by middle of next week

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Tonight - Thursday: Scattered Showers, Cooling Down

The latest radar shows scattered showers across parts of New York and Pennsylvania. Scattered showers are possible throughout tonight and Thursday at times with mostly cloudy skies persisting; originally, Thursday was expected to clear out, although the front will fail to progress as far south as originally expected, instead slowing down and stalling over the region rather than dropping south and then retreating north. Temperatures on Thursday will reach the upper 60s to low 70s inland and the low to mid 70s across the rest of the area.


Friday - Monday: Cloudy, Chilly, Rainy

A weak wave of low pressure is expected to move through the region, producing a round of rain on Thursday night into the first half of Friday. There is still some uncertainty regarding exactly where the heavier rain axis sets up and how much rain falls, which will also influence the temperatures, although at this time there is a high probability of at least a steady moderate to locally heavy rain to focus from NYC and further north/west especially in the first half of Friday. If the currently modeled scenario verifies, high would end up in the mid to upper 50s north/west of NYC and in the low to mid 60s from NYC and further east. Some of the latest models are further north, however, with the latest NAM run taking almost all of the rain north of the area with highs in the upper 60s to low 70s. For tonight's forecast, I am siding with a scenario north of the model consensus, with highs potentially in the mid 60s inland and the upper 60s across the rest of the area. With the aforementioned uncertainty, the forecast is still subject to some changes. Stay tuned for more information on Friday's forecast with updates on Thursday.

It does not appear that a stronger organized area of low pressure will develop, although showers and clouds will persist across the region throughout the weekend, mostly focusing over New England but with scattered showers across the area, mainly east of NYC but extending west of NYC occasionally as well. Temperatures will be slightly warmer, in the mid to upper 60s on Saturday with more widespread upper 60s on Sunday, perhaps getting into the low 70s in the immediate NYC area. Additional showers are expected for Monday with highs similar to those of Sunday. More information will be posted on this time frame as details become clearer.

With the additional chilly temperatures expected, the possibility may be there that parts of the area could end up slightly below average for the month of September; since early 2011, the majority of the area failed to have any cooler than average months. More on this possibility will be posted over the next few days.


Longer Range: Warming Up

The persistent trough pattern that has been in place since 9/15 is expected to break down early next week, with a less amplified pattern returning as ridging temporarily rebuilds into the East. A surge of warmth is expected to move into the region with temperatures reaching the 70s across parts of the region, including NYC on Tuesday, and a larger part of the region on Wednesday. Afterwards, model differences emerge again, with the GFS quickly bringing a cold front followed by a strong cold air mass, while the ECM and CMC keep a warm pattern in place through next weekend. At this time, I am considering the 18z GFS scenario a likely outlier, with a strong cold pattern unlikely to return in the medium range. Stay tuned for more information on the longer range outlook.

Sept 25, 2012: Rain Expected This Weekend

Forecast Highlights


- Some showers on Wednesday, brief warm up
- Chilly pattern continues through medium range
- Rain expected for this weekend

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Tonight - Thursday: Some rain, then cloudy

An area of showers is currently approaching the region, and will provide some rain across the area tonight. Mainly cloudy skies are expected to continue for Wednesday and Wednesday night with scattered showers but with generally light totals up to 1/4 inch for most places. Highs are expected to warm into the mid to upper 70s from NYC and further north/west and the mid 70s east of NYC. Temperatures may reach 80 degrees in parts of the immediate NYC area. Partly cloudy skies are expected on Thursday with the risk of isolated showers and highs cooling down into the upper 60s to low 70s inland and the low 70s across the rest of the area.


Friday - Beyond: Some Rain, Chilly Temperatures Expected

The briefly drier conditions will only be short lasting as another rain event sets up for Friday into the weekend. A closed 500mb low will drift towards the region as a surface low pressure develops off the coast. An initial round of rain is expected on Friday, with mainly cloudy skies, occasional showers and highs only in the 60s across the area; at this time, I am keeping highs in the mid 60s, although this may need to be adjusted lower should the rainier scenario verify. Uncertainty then increases for the weekend as there is still uncertainty regarding the exact development of the low pressure; the latest GFS run goes back to showing the old scenario of a stronger low pressure developing and tracking north through the region, producing widespread rain, while the ECM, CMC and NAM show little additional rain. Although at least some rain is expected during the weekend regardless of which scenario verifies, the scenario first mentioned is still uncertain, and at this time my forecast maintains a chance of some rain for the weekend, although the outlook is still subject to change. Temperatures will remain chilly, generally in the mid 60s to low 70s, although should the rainier outcome verify temperatures would be colder. Stay tuned for more information on the weekend outlook.

Sept 24, 2012: Some Rain, Then Chilly Again

Forecast Highlights:

- Some showers on Wednesday; cooler ending to week
- Chilly rain possible around weekend

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The 5-Day Forecast page has been updated tonight for the entire area.

Tuesday - Wednesday: Slightly warmer; some rain expected

Following the cool air mass that resulted in widespread highs in the mid to upper 60s across the area today, cooler lows are expected tonight with less cloud cover, dropping into the upper 30s inland, low to mid 40s in interior parts of NE NJ, SE NY and southern CT and typically cooler parts of eastern Long Island, mid to upper 40s in the closer suburbs of NYC, and low to mid 50s in NYC. Areas of frost may be possible for interior areas; should this verify, it would be the first frost of the fall for the area. Mostly sunny skies are expected for Tuesday with highs reaching the low to mid 70s across the area.

An approaching cold front will bring increased cloud cover overnight with some showers expected for Wednesday and Wednesday night. Highs are expected to reach the low to mid 70s across most of the area with mid to upper 70s in the immediate NYC area. Overnight lows will be in the 50s for most of the area with 60s in NYC and its surrounding suburbs as cloud cover and scattered showers persist.


Thursday - Next Weekend: Chilly; Dry Start, Potentially Wet Ending

Behind the cold front, another trough will enter the region, although in this case as a more progressive pattern returns with less western Canada and western Atlantic ridging, the trough will be flatter and less amplified than the previous troughs, failing to drop much into the region while the cold front stalls near the central Mid Atlantic, keeping at least partly sunny skies in the forecast for Thursday and Friday. Highs will reach the mid to upper 60s across most of the area with some low 70s on Thursday, slightly warming up on Friday, with overnight lows likely to drop into the low to mid 40s inland and the mid 40s to 50 degrees across the rest of the area with low to mid 50s in NYC.

Uncertainty increases for the weekends as a closed 500mb low moves towards the region but with each model showing a different outcome. Some of today's model runs initially showed a coastal low pressure developing offshore and moving north into the region, providing widespread rain, although have since backed down from that scenario. The general outlook for this time period has a somewhat higher confidence level, with at least some showers expected around Saturday and/or Sunday, with temperatures staying chilly, generally in the 60s to low 70s. The expected set up is more uncertain, however, and at this time there are too many differences to make a high confidence call. Stay tuned for more information on the weekend set up.

**No Update Posted 9/23/12**