Off Topic: Winter of Extremes Not Done Yet

Major Northeast US Snowstorm Likely Wednesday Night through Sunday Afternoon

A forecasting nightmare is unfolding in the Northeast as an extremely blocked pattern again develops thanks to the continuation of abnormally high upper level heights (ridging) over the northern polar latitudes that has dominated the winter season since mid December. Underneath a strong blocking ridge over Northeast Canada and the far Northern Atlantic Basin, a series of intense short wave troughs is expected to dive southwest from Central Canada, each one further deepening a new developing polar vortex over New England.

The first such disturbance is making its way into the region now, bringing rain and snow Pennsylvania and New York (as well as Southern New England), however, this first impulse is the least of our concerns. This complex situation begins with too much warm air from the Atlantic involved in the pattern to allow for significant accumulating snowfall in the big cities of the Northeast. It's the second piece of energy that is expected to entrain some moisture from the Gulf of Mexico and Western Atlantic and rapidly intensify. Numerical weather prediction models are helpless to accurately forecast the exact strength and position of this new surface low. No confidence may yet be provided to any specific snowfall forecast. However, here is what we do know.

1) The second impulse will begin bombing out off the North Carolina coastline Wednesday evening and make its way northward from there through the night.
2) The I-95 corridor from Baltimore southwestward is unlikely to get significant snow from this second storm system as conditions are not right for development until it is significantly further north.
3) Cold air from truly Arctic origins will begin feeding into this developing trough over New England as early as Wednesday Night, however the full effects of this resurgence of Arctic air will likely not be felt until the storm has cut off. The exact location of where the storm stalls will determine who gets the heavy snows and who gets too much Atlantic air intrusion and sees mostly rain.
4) The coldest air during the heart of this storm will *NOT* be to the north of the surface low. It will in fact be to the west and SOUTHWEST of the center. The storm is so blocked and wound up by Thursday afternoon that warm air form the Atlantic will wrap all the way around it and Cold air will be pulled underneath it into the Mid Atlantic states.
5) Folks in the higher elevations of the Northeast will be seeing a potentially devastating heavy wet snow, whether or not they are west of the surface storm. Because the storm is unlikely to move once it cuts off over the Northeast, snows will persist and only gradually diminish in intensity and areal coverage from Thursday morning right through the day Sunday. A four day blizzard could easily result in the Adirondacks, the Green and White Mountains, the Berkshires, and the Poconos seeing as much as 3-6 feet of snow.
6) Someone on the southwest side of the storm in the coastal plain will likely see a major mesoscale snow band and receive in excess of a foot of snow. The exact "slam zone" away from elevated terrain is not at all clear at the present time, but if you live anywhere from Worcester, MA to New York City, NY to Philadelphia, PA to Elmira, NY, you are under the gun for the possibility of such an event.
7) The storm will likely produce hurricane force wind gusts over the open waters of the Atlantic, and tropical storm force wind gusts over land, particularly along the east coast of New England and on Long Island. In fact, to the casual observer, the storm will probably take on the appearance of a hurricane on Satellite imagery. Though it is not tropical in origin, it will develop an eye-like feature and have spiral bands of rain and snow wrapping all the way around it at its' most intense. This dynamic situation also favors elevated convection and could produce thundersnow.
8) Flurries and squalls will persist through Sunday as the entire region is overwhelmed with arctic air and the storm dies.

You folks in DC and Baltimore are missing one of the great late-winter storms of our lifetime. But fear not...the season is far from over. Looking longer term, the end of next week hold promise for the entire I-95 corridor.

EDIT to add: Model consensus is finally beginning to emerge with this storm...it looks like the further west, more amplified solution is favored, meaning areas east of a line from Brooklyn, NY to Springfield, MA to Eastport, ME are more likely to see rain than snow with the heaviest precipitation on Thursday and areas from Philadelphia and perhaps even Baltimore across much of Central PA and NY are most likely to see the heaviest snow.