Saturday, January 21, 2017

Strong Storm To Impact Region Monday-Tuesday

The best way to kill time before a big Pats playoff game is to track a big weather system that is forecast to track up the East Coast,  I imagine the readers of this blog are 60/40 in favor of snow for a variety of reasons.  Winter weather is a source of income for some, a headache for parents of school children, a burden to lesson planning for teachers (yeah right they love it), wonderful to a few and a pain in the ass to others.  This storm is a rain and wind maker with little in the way of frozen precipitation.  A general 1-3" of rain is expected in Southern New England.
WPC Forecast Precipitation through Wednesday 1 AM (image Weatherbell)
Meteorological Discussion/General Overview
I am going to get a bit technical here so feel free to skip to the next section if you are here for dinner and don't care about the recipe,   A piece of energy from the large storm battering the west coast has broken off and is currently tracking through the 4 Corner States.  At the same time, one upper low is tracking northeast from Iowa into Minnesota and Wisconsin.  A severe weather outbreak is occurring in the South as energy in the Gulf of Mexico is tracking across a stalled boundary that drapes from Texas to South Carolina.  Dew points south of this boundary are in the mid to upper 60's.  
NOAA/NWS/NCEP GOES water vapor satellite 
 Energy in Texas will combine with the 4 Corner energy to produce severe weather for all of the SEC conference states.  Large hail, damaging wind, and tornadoes are all possible today and tomorrow.  The Western Mountains are stretching the upper-level energy as it tracks east.  This shows up well on the 500 mb chart which is roughly 18,000 ft up in the atmosphere.
12z GFS 500 mb heights, anomaly Saturday 7 AM (image Weatherbell)
The western upper trough strengthens as another storm unloads on the West Coast.  At the same time, an upper-level ridge will build all the way to Hudson Bay.  This will prevent any Arctic or Canadian air from helping deliver a colossal snowstorm.  The energy emerging from the 4 Corners develops into a closed upper low as it crosses through Texas and Oklahoma.
12z GFS 500 mb height anomaly Sun 7 AM (image Weatherbell)
At the surface, the low is centered in Arkansas by 7 AM tomorrow.  There will be more heavy rain across the South.  The severe weather threat shifts east to the South Atlantic coastal states tomorrow.
WPC Surface Fronts/Precipitation Sunday 7 AM
By Monday AM the ULL will have parked itself in Virginia/North Carolina.  The surface low will not be that far behind.  The storm will be large with multiple competing centers fighting for energy as it arrives in Southern New England.

Short Term Forecast
Forget about the storm for a second.  GO OUTSIDE!  Winds have shifted to the west which is clearing the low-level moisture that kept the clouds around this morning.  Temperatures will rise into the mid 50's this afternoon.  Clouds will increase tonight as the Southern storm grows in size,   Temperatures will be in the 40's,  A cold front will sag south resulting in a northeast wind.  This will increase clouds even further and may produce a shower or two.  The record high for the date in Boston is 68 (set in 1906) which is safe for another year.   In that temperature record's lifetime, it has seen the Cubs win the World Series 3 times.

I will have a post on the Patriots and Championship Sunday tomorrow.

Overnight Sunday into Monday
The wind increases Sunday evening as the storm slowing trudges north and east.  Precipitation will be spotty with just isolated showers.  Some spots will be just below freezing so roads will need treatment Monday AM.  The initial precipitation shield will contain some mixed precipitation and ice.  Most of MA is over to rain by 7 PM but it will be slick for the commute in Franklin, Hampshire and Northern Worcester Counties.
12z NAM hires 3km sim radar Monday 3 PM (image Weatherbell)
Temperatures will be in the mid 30's while pouring Monday afternoon/evening.  Winds will ramp up as well with sustained winds 20-30 MPH with gusts to 40 after 1 PM.  Winds become much stronger at the shoreline and across the Cape and Islands.  The National Weather Service has already issued wind headlines.
NWS Boston Noon Headlines
These headlines are expected to expand later today or tomorrow.  The core of the wind moves over the region Monday night and moves to our north Tuesday AM.  The low departs Tuesday and the precipitation is largely gone by 7 AM.

In Summary
A large and powerful storm will impact the region Monday-Tuesday.  1-3" of beneficial rain will fall.  The main concerns are a messy Monday PM commute north of the Pike in the Western/Central parts of the state and damaging winds in Eastern MA Monday PM/evening.  If anything changes I will post about it in my Pats blog tomorrow.

-Zack Green

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