Confidence is growing that many across New England (especially interior New England) may see the first accumulating snowfall event of the cool season Sunday, November 28 into Monday, November 29. This is something which has been appearing within computer forecast model ensembles for several days and is gaining traction within the operational guidance. (Note: I will be using GFS forecast model outputs for illustrative purposes. This does not mean I am favoring the GFS model).
As we move through the Thanksgiving holiday and the upcoming weekend, a pattern change is set to occur across the country and this is hinted at by both the North Atlantic Oscillation (NAO) and the Pacific-North American (PNA). Both oscillations will be going through a phase change with the NAO becoming more negative through the weekend and then more positive and the PNA becoming more positive then becoming less positive. Not only do these changes indicate pattern change, but these changes are typically associated with storminess somewhere across the East Coast:
As a ride pumps up across the West a trough digs and amplifies across the Northeast. A potent piece of shortwave energy associated with the amplifying trough dives southeast across New England...perhaps as far south as Long Island. Due to the strong baroclinicity which exists between the still warmer waters off the coast and much colder air over land in the fall/winter/spring this can favor the rapid development and strengthening of a low pressure (cyclogenesis):
The warm sector of the system may be characterized by temperatures about 5,000 feet above the ground as warm as +2C to +5C while temperatures on the cold side of the storm as cold as -4C to -9C. This would result in a strong baroclinic environment across the region favoring rapid strengthening and very strong lift (upward vertical motion):
Given this is still several days away it is way too early to get into any specifics or details as many questions need to be resolved. Some of these questions include;
1) Where does cyclogenesis occur?
2) Where does the low pressure track?
3) How quickly does a low pressure develop and materialize?
4) Do any mid-level low pressure circulations form, and if so, where do they track?
These questions would determine who sees snow, how much snow may occur, and where the heaviest/highest snow totals occur. Obviously, given the time of year the most favorable areas for plowable snow (>3-4'') would be across the interior (moving away from the coastline).
This signal has been growing stronger over the past few days and now we work to resolve these (and additional questions) over the next few days.
