Monday, December 05, 2011

Showery In Spots Later Tonight, Snowy for Some Wednesday Night?

The slow-moving cool front that is going to take its sweet time to cross the region -- it's going to be a part of our weather through Thursday -- is bringing its first shot of showers to parts of our region later on this evening. Odds favor this round of rain to pass generally to the north/west of Philadelphia -- with the Lehigh Valley, Poconos, and Central Pennsylvania the beneficiaries of showers from the interaction of warmth aloft, a disturbance riding the front, and the boundary itself.

Steadier rains will fall back to our west and northwest -- generally across Western Pennsylvania and into Upstate New York -- but showers will ride northeast to the east of the frontal boundary and impact the I-81 corridor and Lehigh Valley later on tonight -- generally after Midnight into the early morning hours on Tuesday.   We can't completely discount the presence of a couple of showers even into Philadelphia late tonight or in the early morning hours on Tuesday -- however, the majority of showers that looks to fall later on tonight should be to our north and west.

With the front slowly crossing the region Tuesday night into Wednesday, its position to the south of us will yield cooler temperatures working into the region for Wednesday night and Thursday.  Computer modeling still hints at the potential for rain and/or snow, depending on how far south the front slips, how intense the low pressure center is, and how heavy the precipitation is that traverses along the front.  Most of the heavier and steadier precipitation is modeled to fall south and east of the city but surface temperatures will probably be a bit too warm for all snow south/east of I-295 in Jersey.  The NAM, shown above, is arguably the most aggressive scenario at this point but given that the model is projecting out towards the end of its forecast cycle (60+ hours for a model that only predicts 84 hours out) it isn't at its most accurate or reliable.   If threading the needle were ever a meteorological phenomenon, this wave on early Thursday may provide a photo for the dictionary.

In terms of potential accumulations, some parts of the region could see a few inches of snow...mainly higher elevations, with generally anyone north/west of 295 in New Jersey getting a shot at seeing some snow stick on Wednesday night.   There's still a lot to look at in the coming runs and it's not a "lock" yet but there's definitely a wintry event to keep an eye on.