Winter Storm Watches Downgraded to Winter Weather Advisory

The storm that looked so promising (for snow lovers) early in the week has largely trended warmer and weaker.  I'm not a fan of changing a forecast because A) it means I was wrong and B) no one likes a flip flopper.  None the less when there is no support left for a 48 hour forecast I must blow it up and start over.

NWS Boston watches/warnings

The National Weather Service has downgraded its Winter Storm Watches to a Winter Storm Advisory.  The NWS likes this for snowfall totals

NWS Storm Forecast

Often times a more southerly storm track will lead to a colder solutions.  High pressure is not found in the ideal location; its too far east

HPC surface analysis (NOAA)

The high is over Hudson Bay and another high in Quebec near the Gulf of St. Lawrence.  That is not allowing for a true northerly flow.  Current Temps

2 m Temps Analysis 9 AM (image weatherbell)

As the weak low pressure lifts north it will warm the upper levels too.  It should be mostly wet from Springfield to Worcester to Boston overnight.  If any heavier bands of precipitation develop and make it onshore they could create enough cold air to push the rain/snow line back.  There is a lot of moisture to work with

East Coast Radar 

The precipitation will not begin until later this afternoon.  The majority of the snowfall will be Sunday.  It will not be from the storm but rather an interaction between low pressure in the Great Lakes and the departing storm.  The Southern Maine/NH seacoast/Northeastern MA may actually do quite well Sunday/Sunday night.  York, ME and surrounding area's may get over a foot!

12z NAM 1000-500 thickness, mslp. precip valid Sunday 7 PM

See how the low is departing? Check out the 500 mb level

12z NAM 500 mb vorticity valid Sunday 7 PM

A band of heavy snowfall will form along this boundary.  Exactly where this sets up will be a challenge and I can see a scenario in which Portland, ME receives 4 inches while Scarborough, ME gets a foot.  There will be large differences within a small area.  Here is what the NAM hires is printing out (I've heard the NAM compared to a closer by some meteorologists which is a great analogy.  Inside 24 hours the model is money)  

12z NAM hires total snowfall (image weatherbell)

The EURO control is in with the same type of idea for Sunday into Sunday night but has a bit more snow into Massachusetts.  So here is my updated snowfall map

Second Snowcast for 02/24/13- ISOLATED HIGHER AMOUNTS IN PINK/PURPLE

Finally stay tuned! There is more active weather expected next week.  I will update this weekends storm as needed and will post on next week tomorrow morning.