Cold air, snow showers to close out the week

This holiday week has generally been characterized by the return of colder air (after quite a warm start from the tail end of the weekend) and chances for light snow. Much of the same will continue on Thursday, as temperatures in the 20’s to near 30 will be common during the afternoon and a weak disturbance passing through aloft will spark the development of snow showers throughout the area. The weak low pressure system forming offshore and the relative lack of moisture means that precipitation will be spotty at best — but nevertheless, some flakes should fly especially across New Jersey and much of the interior. Accumulations are expected to be extremely light.

Another cold night is expected from late Thursday into Friday, as the aforementioned developing low pressure system pulls down one more reinforcing shot of cold air. Low temperatures in the teens and 20’s should be rather common by early Friday morning. Despite the light snow over the past several days, the weather pattern has been generally quiet. But beginning with a storm system late this weekend, the activity looks to kick up once again as we make our way into January.

Northeast US surface analysis on December 26, 2013 showing a weak coastal low forming offshore.

Northeast US surface analysis on December 26, 2013 showing a weak coastal low forming offshore.

Forecast models have come into better agreement on the development of a low pressure system later this weekend, which will track up the East Coast on Sunday into early Monday. The system is forming as a result of a southern stream disturbance, a moderately strong shortwave, which ejects northeastward from the Southeast United States and is pulled up the East Coast. This system is, by definition, a Nor’easter — but currently doesn’t look to act like a winter-time one.

gfsNE_sfc_prec_090

GFS model forecasting the development of heavy precipitation near a low pressure system just off the NJ Coast on Sunday night.

Much of the reason for this is the lack of antecedent cold air throughout the Northeast. Despite the cold air currently in place, the evolution of the pattern suggests that this air will be scoured out rather quickly. An initial disturbance tracking over the Great Lakes (well to our north and west) will induce a southwesterly flow in the mid and low levels, and warm air advection will bring 850mb temperatures to near 5C. As the coastal system tracks up the coast, the next reinforcing shot of cold and arctic air will still be over the Northern Plains. So, despite the system taking a track which historically provides the area with wintry weather, it seems more likely that rain will be the dominant precipitation type. 

GFS model forecast temperatures at 850mb level during heavy precipitation, showing very warm air in much of the area -- precipitation falling as rain.

GFS model forecast temperatures at 850mb level during heavy precipitation, showing very warm air in much of the area — precipitation falling as rain.

There is still some potential for wintry weather across the elevated and far interior areas. But near the coastal plain and even much of the area suburbs, confidence is increasing in rain event from Sunday into Monday. Of course, we’ll be watching and analyzing carefully for any potential changes to the pattern and evolution of the storm system. Stay tuned both here and to our social networks for updates.

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