Wednesday, December 8, 2021 Connecticut Snowfall Forecast

 Forecast models have been in general agreement for several days in the potential for accumulating snow Wednesday. While there continues to be uncertainties regarding overall strength and track there is a growing consensus and several signals which indicate an area of low pressure will not only track far enough north to overspread the state with snow, but for the low pressure to strength enough and in time to result in a band of moderate-to-heavy snow traversing at least a part of the state. 

A strong upper-level jet places the region in a very favorable position for enhanced upper-level divergence. This will work to strengthen the low pressure system and support large scale upward vertical motion (favorable for the generation of precipitation):

One of the key players here is the interaction between shortwave energy and the amplification (strengthening) of an upper-level trough as it moves across the Ohio Valley. Should this shortwave trough amplify (as the NAM continues to suggest ) earlier this would increase the degree of large-scale lift across the region along with aid in the faster development of the low pressure. This is a signal which appears to be strengthening:

Forecast models are also in general agreement an 850mb closed low pressure circulation will pop just south of Long Island. This indicates system strengthening and would also place a good portion of Connecticut, Rhode Island, and eastern Massachusetts in a potential path for a band of moderate-to-heavy snow to traverse. This is also highlighted by strong 850mb vertical velocities:

There is still plenty of room for this to trend in a direction which favors less snow, however, the signals are pointing towards we may end up in the direction of accumulating snow. In fact, it is very possible snowfall totals (map below) may have to be adjusted upwards by an inch or two. 

What can we expect Wednesday?

• Snow starts off around daybreak Wednesday (maybe a bit later) across much of the state with snow very light. 
• Snow intensity gradually begins to increase through the morning. 
• The heaviest snow rates occur under where the band of snow traverses and the timing of this is between about 11:00 AM - 3:00 PM Wednesday. Snowfall rates could approach 1'' per hour during this window.
• Snow begins to wind down moving into the late afternoon with some flurries and light snow continuing into the evening. 
• Travel will be slick so give yourself extra time traveling. Travel impacts should not be severe but plan accordingly. 
• Below is my first call snow map, however, keep in mind adjustments are likely Tuesday afternoon.