First Winter Storm of 2014-2015 Set to Impact Connecticut

The first winter storm of the 2014-2015 season is only several hours away from beginning across Connecticut and the timing couldn't be any more opportune as we approach the Thanksgiving holiday.  We are also looking at a timing in which the most substantial impacts will occur from mid-to-late morning through early evening.  While this will be a fairly quick hitting storm, lasting for maybe 12 hours or perhaps a little less, the timing will cause major travel problems.  When forecasting winter storms across the state, they can often times be challenging as we often deal with the possibility of mixed precipitation such as sleet, freezing rain, and rain.  This case will be no different.

Brief Technical Look

A strong piece of shortwave energy is moving through a fairly deep digging trough as it progresses eastward across the United States.  The shortwave will be responsible for a developing area of surface low pressure just off the southeast coast.  As the area of low pressure moves north/northeastward it will strengthen:

Discussion

Computer forecast guidance are all in very strong agreement that the surface area of low pressure will pass just to the southeast of southern New England.  This storm track favors heavier precipitation impacting the state of Connecticut.

Surface temperatures across the state will be confined to about the lower to mid 30's from southeastern CT to more lower 30's elsewhere, with the exception of the Litchfield Hills where temperatures will be into the upper 20's to near 30F.  This indicates the snowfall will be more wet in nature and heavy in nature.  However, across the Litchfield Hills the snow will have a bit more fluff factor to it.

The main questions we are presented with is what happens with the mid-level temperatures, particularly, between about 8,000ft and 12,000ft.  While the surface low pressure is going to track southeast of the state, the developing area of low pressure at 700mb (roughly 10,000 ft AGL) is expected to not only track over CT but intensify as it does so:

This feature presents some trouble as with warmer air now working in aloft, this will eventually lead to a transition from snow to sleet across portions of CT.  However, it's a little uncertain as to exactly where this snow/sleet line will setup.

If the 700mb low not only develops earlier and intensifies quicker, this will mean a further surge of warmer air across the mid-levels over more of the state, meaning more locations transition over to a mix of snow and sleet which would reduce snowfall totals a bit.  However, if the 700mb low develops a bit later and doesn't intensify as quickly, the warmer air won't move much further into CT than the eastern portion of the state,  This feature will also allow for a pretty big snowfall gradient across the state in terms of accumulations.  

One point of interest is the track of the 850mb low with respect to CT.  While the system will be a quick hitter, typically something that can preclude much higher snowfall totals, computer forecast guidance indicates the 850mb low will track just to the southeast of CT,  As this occurs, this will favor a period of extremely strong low-level lift moving through the state of Connecticut meaning there will be a period of very heavy precipitation rates across the state.  This is when the majority of the snowfall accumulations will occur.  

Forecast

• Precipitation breaks out statewide between 6:00 AM and 8:00 AM
• Precipitation may begin as all rain, especially southern CT with more of a mix across the rest of the state.  
• Precipitation will quickly changeover to all snow with the exception of southeastern CT
• The heaviest of the snowfall will occur between 11:00 AM and 6:00 PM.  This is when snowfall rates will approach 2'' per hour and perhaps may even briefly approach 3'' per hour.  
• The highest snowfall totals should be confined to areas along and west of I-84.  This is where precipitation will remain mostly snow, however, some mixing is possible towards the end.  
• The storm begins to wind down between about 6:00 and 8:00 PM.