White Christmas Forecast Update

No need to really get too scientific with this post as that was done yesterday but this post will reflect some minor changes to my forecast from yesterday along with discussing the potential for some thundersnows which could occur with a rather intense band of snowfall which may push through portions of the state during the early morning hours tomorrow (between 6:00 AM and 9:00 AM). Several mesoscale computer forecast models develop a very intense band of snowfall on the backside which could drop a couple inches of snow (along with thunder, lightning, and strong wind gusts) in just a short amount of time. Due to the fast moving nature of this potential band this will reduce the likelihood for significant snowfall accumulations:

There are still some uncertainties with regards to how far into the state the warm air gets and this leads to some uncertainties with where the rain/snow line will setup. This will be very critical because locations near this line can be looking at as little as an inch or so of snow or as much as 4-5'' of snow. Unfortunately this is not something that will not be pinned down until the event is ongoing.

What could be a rather underrated aspect of this event is the potential for strong to damaging wind gusts as the system departs. Computer forecast models indicate the potential for wind gusts between 50-60 mph for a time tomorrow afternoon:

Given the potential for wet snow which would stick to limbs and power lines, this combined with strong wind gusts could yield a quite a bit of downed limbs and power outages beginning tomorrow morning and lasting through the afternoon. Areas which see any water refreeze on tree limbs and branches tonight could be especially vulnerable.

What should we expect with this storm?

• Snow flurries begin to work into the state between 10 AM and 1:00 AM. Any snow should be brief along the southeast coast as warmer air will be in place and continuing to work in. 
• Light to moderate snows work into the state after 1:00 AM. At this time much of southeastern CT should have changed over to rain. 
• Also after 1:00 AM, we will begin to see warmer air in the lowest 5000' of the atmosphere work into the state, this will transition snow to a mixture of sleet and even some freezing rain in spots from the southeast to the northwest. The rain/snow line is projected to come very close to the I-84 corridor. The further to the north and west of I-84, the more likely you are to remain all snow. 
• After 5:00-6:00 AM we will begin to see some areas further south and east along I-84 transition back over to snow as colder air works back in. At this time, mesoscale computer forecast models suggest a VERY intense band of extremely heavy snowfall will push through a good portion of the state. Within this band snowfall rates could approach or even exceed 3'' per hour!  This will make for white out conditions. Also, given the degree of upward vertical motion within this band and even some very weak instability, the possibility will exist for thunder, lightning, and strong wind gusts as well within this band. If these convective elements happen it could only enhance the snowfall rates. 
• Given the natural of the thermal profile, the snowfall ratios will not be great and the snow will be more wet in nature (the exception here could be the northwest hills). This will allow for snow to stick to power lines, utility poles, and tree limbs. This combined with strong to damaging wind gusts beginning late morning will yield numerous pockets of tree damage, downed power lines, and power outages. 
• The snow will begin to taper off after 9:00 AM to 10:00 AM and should be out of the state by noon with perhaps a few leftover flurries around.