Thursday, February 21, 2013

Short Term Forecast/Weekend Update

For the third straight weekend there is a Nor'easter for meteorologists and weather enthusiasts to track (early heads up-something wild next weekend is lurking to make it 4/4).  For the first time this year a rain/snow line will try to work north and west.  I think it will struggle to get past 495 or north of the Pike but those areas will see a brief mix with rain or sleet.

Short Term Forecast
After a cold start temperatures will only rebound into the upper 20's/low 30's
NWS Tauton 7 am low temps
As I mentioned yesterday high pressure over Central Canada moved to its east so we will be under the influence of more direct Northwesterly winds
HPC Surface 0530 am EST
I've drawn the path of a major, potentially record breaking snowstorm in the plains and the wind flow around the high.  First of all the wind flow around the high will support temperatures like this
08z RAP 2m Temp valid 4 PM EST (image weatherbell)
Overnight lows will drop into the lower 20's/upper teens.  By Friday the track of the Central storm (aka "Q") will lift some warmer air into New England.
06 NAM 1000-500 thick, mslp, precip Fri 1 PM EST (image weatherbell)
Weekend
We will not be getting "Q" but the ultimate track of "Q" will play a role in the track of our storm.  Here is what should happen at the 500 mb level

Tonight 7 PM
00z GFS 24 hr 500 mb vort
Tomorrow 7 PM
00z GFS 48 hr 500 mb vort
Saturday 7 PM
00z GFS 72 hr 500 mb vort
Sunday 7 AM
00z GFS 84 hr 500 mb vort
So what will happen at the surface is the low will work its way into the Wisconsin/UP of Michigan and weaken.  Meanwhile energy will round the base of the trough through Texas and develop a new surface low in the Southeast which will move off the east coast and head up the coast.
00z GFS 850 T,, mslp, precip Sunday 4 am
The question is will the High pressure up by Hudson Bay be strong enough to keep most areas cold.  Given that the NAO is negative I tend to think the storm will not be able to come to far north as shown by the EURO ensemble control (I cannot show that even though I pay money to look at it).  HPC has the storm over the Cape by Sunday morning
HPC Sunday morning forecast
Here is what I am expecting (updated a tad)
General expectations (2)
No amounts yet, you'll have them tomorrow.  That blue and pink may feature plain rain for a time as the center makes its closest pass and wraps warm air in.  The Atlantic Ocean, though warmer than average, is still cold. If need be there will be an afternoon update, if not see you tomorrow morning!













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