More finely tuned details for December 1-2 storm

No need to beat around the bush with a big storm bearing down the east coast. By now, I had hoped we would have reached some sort of decisiveness regarding this event but for now, it remains very much on the fence between a garden variety, easily forgotten weather system and a more memorable early December winter storm. The pieces are coming together as expected with the storm, as of Saturday, spinning its way through the upper Midwest. The emergence of a coastal low pressure center by Sunday evening will ultimately make this a big east coast precipitation producer but the track of this coastal system is expected to stay south of Long Island and south of Cape Cod, at least for the time being. This would keep the heaviest zone of snow south of the northern half of Vermont, especially since the well-established jet stream level support for this storm, otherwise referred to as an upper level low, is expected to move due east and take the east coast "escape hatch" out over the Delmarva. This feature is then expected to take a turn northeastward but it would be too late for the Mad River Valley to procure an epic snow event; instead, it would be a smaller event. It is very close however and between Friday afternoon and Saturday afternoon, models have been suggesting that the zone of best snow would be a little farther north. Southern Vermont is in fact in one of those "best zone" areas and if the storm would track another 50 miles farther north, it could really turn the outcome. So I can throw out some expectations as it stands now and simply throw it out there that things could certainly change for the better.

So with the big picture situation established the particulars are as follows. Snow should begin Sunday evening and fall moderately for a time before midnight. As the coastal low pressure center intensifies and assuming it tracks as predicted, the precipitation will consolidate over southern and central New England and the snow will dissipate somewhat over northern Vermont. By Monday morning, the zone of heaviest snow is expected to be situated over the Catskills, extreme NE Pennsylvania and eventually extending into southeast New Jersey. As both the surface and upper level features associated with this big east coast storm move northeast, the heavier snow will also push northeastward and again impact much of Vermont, especially the southern half of the state. Mad River Glen will get some of this as well with the heaviest snow falling Monday afternoon and evening. Total snowfall with this storm track is likely to be in the 8-16 inch territory. Snowfall totals could reach two feet over the high country of southern Vermont and certainly over the Catskills of New York state. The intensity of the storm will certainly allow for very blustery conditions through Tuesday.

Sub-freezing temperatures are expected to continue for the balance of the week but significant snow is unlikely. Flurries are expected to continue through Tuesday and weather disturbance passing to the region's south will spread some snow showers into the state Wednesday night and those will continue into Thursday. A more intense shot of arctic chill is expected to arrive Friday evening and with that could come some more light snow or snow showers through early Saturday.

The longer range outlook, beyond next weekend looks more mediocre as of now. The two most glaring things is the lack of high latitude blocking quantified by a rising AO index. The EPO, which for much of November remained largely negative and was defined by a loose Pacific Jet, will neutralize, allowing the Pacific jet to become more active. These two changes will limit the influence of arctic cold in mid-latitude North America. That said, there are no indications we are moving into full blown "el torchy" mode. I would expect 2-3 fairly mild days between December 8th and 18th which is not atypical in a Vermont December. The pattern also continues to look stormy and snowfall will thus remain a possibility in spite of a more zonal jet stream pattern.