Small-Moderate Snowfall tomorrow

Temperatures have varied in 2013 so far for Southern New England.  We opened with a cold stretch that dropped temperatures close to 0 for many of us.  We rebounded with temperatures in the 60's yesterday.  Yesterday was a tease as snow is in the immediate forecast with cold to follow.  There is high confidence in a flip to below normal temperatures beginning tomorrow.

2013 Year to date Temp Anomalies (image wxbell)

So far we are approx 0.05 C above normal in North America.  The eastern warmth has been nearly offset by stubborn western cold.  The first step to changing this will be to breakdown the southeast ridge.  A nearly stationary cold front is working through the South.

Surface Map 4 AM EST

I've circled two areas of high pressure and a wave on the stationary front.  Today that wave will begin to deepen and work its way towards the northeast.

2 m Temps 5 am EST (image wxbell)

One can see the likely track of the system.  The ultimate track is important for where the rain snow line develops.  Right now I'm thinking it will set up in a similar location as the late December quick hitter.  This is not a storm with great upper level support but none the less a weak surface low should develop.  The Jet Stream tomorrow looks like

06/15 NAM 250 stream valid 1 am Wed

Notice the jet really digging into Texas before ejecting over the ridge in the SW Atlantic.  At 500 mb the flow remains strong but without any vort maxes.  Vort maxes are found with a shortwave at the 850 mb level

06z/15 NAM 850 vort valid 1 am EST Wed

A good area of low level upper motion should result in good snow zones tomorrow.  Here is the 850 temp for the same time

06z/15 NAM 850 mslp, T valid 1 AM Wed

The zero line is forecast to stay close to the coast by the NAM.  The EURO brings it further inland but the cold air will remain dense and in place with the high to the north in southern Ontario.  Here is the EURO ensemble temp forecast for tomorrow, usually one of the most reliable temperature models

00z/15 EPS 2 M T max valid 1 PM Wed (image wxbell)

So I buy the NAM totals.  Here is the model output for snowfall according to the NAM

06/15 NAM accumulated snowfall valid Wednesday night

The NAM has done pretty well in the short term with snowfall this season.  Sometimes the regional models can get a better handle on unique synoptic setups because they are not as complicated physically speaking as global models.  None the less agreement is good for at least 3 inches south of the Pike to parts of NW RI and NE CT.   I have to say I don't usually disagree with the HPC but I am today.  I think the 4 inch band is further south just to the west of the rain/snow line.

HPC Day 2 snowfall probs > 4 inches

Finally here are some city grams from the GFS around SNE

06z/15 Boston

1-2 inches in Boston

06z/15 Worcester

2-4 Worcester

06z/15 Chicopee

1-2 Chicopee

06z/15 Hartford

1-2 Hartford

06z/15 Providence

2-4 Providence

Those commuting south should stay mostly snow until mid day tomorrow at least.  Update tomorrow morning have a good day, thanks for reading.

City grams image credits- Dr. Ryan Maue and Wxbell.