Sunday night/Monday Storm Update

Confidence continues to increase on another storm system hitting southern New England Sunday night and lasting through much of Monday.  However, latest trends indicate that the further southward you go in southern New England, the less in the way of snow you will see.  While we have a very cold airmass in place currently the storm tracking to our north and west will allow for a strong surge of warmer air to work into the region ahead of the storm.  With this many locations (especially south of the MA Pike) will see a quick transition to sleet, freezing rain, and even plain rain.  While I believe this is the more likely scenario, we can't completely rule out the possibility of more in the way of snow even further south in CT (away from the coast).  This will ultimately depend on the overall strength of the storm and there are some differences within the computer forecast models.

Both the NAM and GFS computer forecast models develop a fairly strong surface low just off to our north west and develops closed off circulations at 925mb, 850mb, and even at 700mb (to a degree).  This is a sign of a rather intense system.  With these lows also tracking to our north and west and with the system so strong it will yield a very strong southerly flow into the region which will bring a surge of much warmer air northward into our region both at the surface and lowest several thousand feet of the atmosphere:

The below images are from the GFS computer forecast model, however, the NAM model is similar

 
Unfortunately I am not able to post Euro graphics, however, the Euro model is far different than the GFS and NAM.  The Euro is not as intense with the system and doesn't really developed closed off circulations at 925mb and 850mb.  This would support less in the way of warm air advection meaning the colder airmass sticks around much longer and this would yield more snow.  This solution can't be ruled out, however, I don't think it is very likely.

There are also questions with regards to the exact timing of the precipitation.  While the front edge of the precipitation may be entering into CT by as early as 8-10 PM the air is still going to be be quite dry so initially the precipitation will evaporate before reaching the ground.  The air may not become saturated enough until close to midnight.  This evaporation and dry air will do a few things; 1) Produce cooling (the process of evaporation produces cooling) which will help keep the air cold enough to support snow 2) This will not offset the surge of warm air advection so if we are seeing strong warm air advection and precipitation is taking a while to reach the ground this leaves a short window for snowfall (especially south of the MA Pike).

Over the next day or so we should be able to fine tune the details on everything.  Based on things right now this is what I am expecting in terms of snowfall across southern New England.  While not likely a major issue, we may have to watch some areas for freezing rain which could yield a glazing.  Below is my map: