More Accumulating Snow in the Forecast

We are going from one accumulating snow event right into another as yet another strong piece of shortwave energy and associative low pressure is projected to dig southeast across the Great Lakes and track either right over CT or just south of Connecticut.  The exact track will be critical as to how much snow falls and where the cutoff is between accumulating snowfall and a mixture of precipitation.

As the shortwave energy tracks over the Great Lakes it will acquire moisture and the low pressure will begin to strengthen rapidly due to a very tight baroclinic zone (very tight temperature gradient in the lower levels of the atmosphere).  This tight baroclinic zone will contribute to a swath of very intense precipitation, whether it be snow or rain:

Both the NAM and GFS forecast models (as well as others) suggest we will see some pretty intense 700mb vertical velocities with the low pressure as it tracks across the area.  As these intense vertical velocities move overhead this will yield a several hour period of intense precipitation (rain or snow) associated with one or several bands of precipitation:

With the possibility for very strong lift associated with bands of precipitation this also means there will be subsequent areas of sinking or or subsidence.  This will actually prevent precipitation from falling to the ground across some areas.  We can actually see this by looking at bufkit.  Looking at this morning's run of the GFS at Windsor Locks, CT notice those blue contours?  These indicate areas of sinking motion.  What we can take from this is if we do indeed see some intense bands there will be areas of sinking motion and that would cut away at potential snowfall totals for several areas:

Keeping with bufkit we will also illustrate just how strong the lifting may be and how this is indicative of the potential for a several period of extremely heavy precipitation.  We will look at Windsor Locks, CT and Worcester, MA to show this.  The following parameters are overlayed; snowgrowth (the purple and yellow contours), omega (with red contours indicating upward motion - the more contours and more negative the value the stronger the lift and blue contours indicating sinking motion - the more contours and more positive the value the stronger the sinking motion), and temperature (the faint yellow/brown contour).  For snowgrowth you want this zone to be between 12,000ft and 18,000ft and want the -15C contour to cross this zone.  When these conditions are met you stand a great chance of generating a great deal of dendrites and near perfect snow growth.  In the case of this system that criteria will be met.  Now to maximize and realize this snow growth you want very intense lift to run through this zone.  Notice how the NAM is showing some very intense upward vertical motion in this zone while the GFS is a little less aggressive  (at least at Windsor Locks):

With this all said what can we expect?  For one, the AM commute tomorrow is going to be quite hazardous as we are looking at the timing of precipitation from around the pre-dawn hours lasting until late morning or even early afternoon (later start and end times the further east you go).  Expect a very slow commute with numerous delays.  Areas across southern CT through southern RI and into SE MA will begin as mostly rain, however, may see a transition over to snow towards the end of the event as temperature begin to quickly crash.  Across inland locations as much as 3-5'' of snow will be possible with higher amounts possible across the higher elevations.  Initially, snow will have trouble sticking to the pavement, however, with heavier intensities of snowfall allowing to further cool the surface, snow may begin to stick to paved surfaces.  At the height, snowfall rates could approach 1.5'' to even 2'' per hour.  Below is a map of what I expect: