Clipper System to Bring Snow on Tuesday

One storm system has moved through and another is arriving as a strong clipper system is set to bring a period of light to moderate snowfall during the day on Tuesday to southern New England.  We aren't looking at a major snow event here, but we are looking at plowable snows.

  A trough will be working into the upper Mid-west region over the next few days and begin to amplify (sharpen) during the morning hours of Tuesday.  As this trough, with an associated Arctic cold front near the region, a piece of rather strong shortwave energy will rotate around the base of the trough.  With the trough amplifying, this will allow the shortwave energy to strengthen even further.  The trough amplifying will also allow for moisture to be drawn into the system from the Atlantic and this system will also have moisture associated with it.  Below is a 4-panel chart from today's 18z run of the GFS valid for 7:00 AM EST Tuesday morning.  The graphic on the top left displays the 500mb pattern (roughly 18,000ft AGL).  Circled is the piece of shortwave energy discussed above.  The graphic on the bottom left displays relative humidity values at 700mb (roughly 10,000ft AGL).  The darker the green shading, the more moist the airmass is at that level.  As you can see we are plenty moist.  The graphic on the bottom right displays 6-HR precipitation values and you can see the area of precipitation working towards the region.

  

Right now we are expecting light snows to break out very early Tuesday morning and lasting through late afternoon.  As stated above, we are not expecting a major snow producing event here given this is a clipper system which are typically very fast moving and they aren't usually associated with a great deal of moisture.
The airmass in place across the region will be cold enough to support snow for the entire region, with perhaps some mixing across the outer Cape.  Snowgrowth looks rather decent as well and snowfall ratios may be as high as 20:1!  This will help us in the snow accumulation department.  Mid-level lapse rates also look to steepen and this coupled with some strong lift which is suggested by stronger vertical velocities moving across the region suggest, there could be a very brief period of heavy snowfall somewhere across the region.  Given what we have presented to us now, this is what to expect right now.