Dec 25, 2011: Rain, Thunderstorms, Wind Return

Notes: A Wind Alert is in effect for the entire area for Tuesday night into Wednesday.

In addition, I opened a poll earlier today, found in the right side of the blog below the regional radar, for the most extreme weather event of the year. To find more information on each event, visit the "Storm Summary" page or this afternoon's post, which included a brief summary of each event. The poll will close on January 4th.

--------------------------------------------------------

With a weak low pressure approaching the region, today brought partly to mostly cloudy skies across the area while widespread snow showers affected the rest of the Northeast. High temperatures were above average, yet normal for the pattern we're currently in, peaking in the lower 40s inland and in the mid to upper 40s across the rest of the area.

Another brief trough will bring colder temperatures for tonight and tomorrow, although an approaching storm will bring more rain for Tuesday night, along with strong winds, temperatures back above 50 degrees and thunderstorms. The rain will end by late Tuesday night, although the wind will stick around through Wednesday, followed by some of the coldest temperatures so far this winter for Wednesday night into Thursday.


Tomorrow's Outlook:


As a colder air mass will move into the region, slightly cooler yet still slightly warmer than average temperatures are expected for tomorrow, peaking in the lower to mid 40s inland and the mid 40s across the rest of the area. Gusty winds are expected as well, with gusts up to 35 mph. Colder temperatures are expected for tomorrow night, dropping into the lower to mid 20s inland and the upper 20s to mid 30s across the rest of the area.


Tuesday - Wednesday: Rain, Thunderstorms, Strong Winds Return


The last storm to bring unseasonable conditions for December into the area was on last Wednesday, when temperatures passed 60 degrees and a squall line brought widespread thunderstorms and some severe weather for parts of the area. Although temperatures will not be as warm, the storm that will affect the region on Tuesday night will bring unseasonable conditions for December once again.

The low pressure will develop over the southern states, moving towards Virginia by Tuesday afternoon. As the storm will be in the process of phasing with the northern stream, it will become more amplified while intensifying and moving NNE, ending up near eastern New York on Tuesday night and west of Maine on Wednesday, although the northern half of the track may end up west of what I am currently expecting. There are currently two main model solutions, with the further east NAM taking the storm just inland, the CMC/GFS taking it over NJ/eastern PA and towards Maine, with the ECM and UKMET further west. Considering the scenario and the latest model trends, I am siding with the further west ECM/UKMET for this storm. When the storm first moves into the region, there will not be much cold air associated with it, but more cold air will enter the storm as it moves out of the region. As a result, the moderate snows will be focused from northern PA into parts of western and northern NY with several inches of wet snow possible. Further south, areas well north/west of I-95 will see a mix of rain and snow, ending up as rain to snow west of the storm track and a mix to rain east of the storm track. Rain is expected to fall across the area.

Forecast for NYC Area: The rain is expected to start affecting the area around Tuesday in the late afternoon, after 3-5 PM, as scattered showers move into the area from the southwest/west. The rain will intensify in the evening, with the heaviest rain expected to fall between 8 PM and 12 AM. At the same time that this happens, a strong low level jet is expected to move into the area. This will result in a scenario where a line of heavy rain moves into the area, with thunderstorms also likely in the immediate NYC area and Long Island/S CT. The low level jet will help to produce strong wind gusts, and while the exact intensity of the wind is still uncertain, for now I am expecting gusts between 40-50 mph in the immediate NYC area, Long Island and southern Connecticut. Wind gusts could exceed 50 mph in parts of the area especially with any thunderstorms, and may potentially end up close to 60 mph in parts of Long Island. For now, I issued a Wind Alert for the area, although an upgrade to a High Wind Watch may be needed. With the low pressure in eastern Pennsylvania, temperatures will steadily warm up as well, and are expected to peak towards 10 PM-12 AM in the mid to upper 40s inland, lower to mid 50s in the immediate NYC area, and the mid 50s across much of Long Island and southern Connecticut.

The storm will not last for a long time across the area, and is expected to end west of NYC between 11 PM and 2 AM and east of NYC between 1-4 AM, with scattered showers possible afterwards. Overall, by the time that the storm ends, at least 1/2 to 1 inch of rain is expected across the area, with amounts locally up to 1.5 inch. Behind the storm, moderate wind gusts are expected across the entire area, gusting up to 30-40 mph at times. Wednesday will bring temperatures steady in the upper 30s to lower 40s inland and the lower to mid 40s across the rest of the area with the winds lasting throughout the day, gusting up to 30-40 mph. Stay tuned for more information on this storm and its impact in the NYC area.


Thursday - Next Weekend: Cold Start, Warmer Weekend


Behind the storm, a stronger trough will move into the region, bringing some of the coldest temperatures so far this winter. With the winds lasing through Wednesday evening, cold wind chills are likely across the area. As a high pressure moves in, the winds will calm down with clearing skies overnight, which combined with the cold air mass in place, will bring temperatures down into the mid 10s inland, upper 10s to mid 20s in the north/west suburbs of NYC, southern CT, and Long Island, and upper 20s in NYC. Mostly sunny skies are expected for Thursday with highs in the lower to mid 30s inland and the mid 30s across the rest of the area, potentially reaching the upper 30s in parts of the immediate NYC area.

As a weak low pressure moves towards the Great Lakes, warmer temperatures will return, reaching the mid 40s across most of the area on Friday and the mid to upper 40s on Saturday with the risk of a few showers on Friday night. For New Year's Eve, partly cloudy skies are likely in Times Square with temperatures likely in the mid 30s. Slightly cooler temperatures will return for Sunday but still in the lower to mid 40s across most of the area.

Looking into the longer range, although the pattern is still overall unfavorable, there are more noticeable changes showing up in the long range models, most notably with more stratospheric warming taking place, which is a factor needed for a colder and snowier pattern to develop. Through the first week of January, above average temperatures are likely to continue with a few storm potentials, one of them possibly around January 2-3, and while the Northeast would still be favored over the NYC area to see snow, it is not out of the question that at least one of the storms in the first 10 days of January brings the second snow event of the winter to parts of the NYC area. There is still uncertainty with the changes showing up in the long range, and it is possible that the pattern stays unfavorable for sustained cold and snow through the rest of January, but if the latest signals are correct, the mid January time frame may be when cold as well as snow/mixed precipitation become more frequent across the region, including the NYC area. Stay tuned for more information on the longer range, especially with the updated winter outlook that will be issued on January 1st.