Wednesday, December 14, 2016

Bitter Arctic Blast On The Way

The National Weather Service Boston office has issued a *High Wind Watch* and a *Wind Chill Watch* for Thursday night into Friday.  Winds will gust 40-50 mph Thursday night into early Friday AM.  These wind gusts will combine with the Arctic air mass to produce wind chills -10 to -20 below zero.  Friday AM will be dangerous for anyone who has to be outside for extended periods of time.  Snow will fall overnight Friday into Saturday AM before changing to rain. By Sunday temperatures briefly return to the 50's.  Buckle up we are on a weather roller coaster.
NWS Boston Headlines 
General Overview
One cold front will cross New England tonight.  This front will drop temperatures 15-20 degrees from where they are today.  This is not the main Arctic front that will deliver the extreme cold and strong winds.  It will not arrive in time to deliver bitter overnight lows.
WPC Surface Fronts/Precipitation Wednesday 7 PM
Lows tonight are cold but manageable.  Temps drop into the upper teens in Worcester County out towards Springfield and into the lower 20's for E MA, RI and CT.
NWS minimum temps Wednesday PM to Thursday AM (image Weatherbell)
Thursday AM is the time to get any outdoor work complete.  Winds will gust 10-20 mph out of the west until about 2-4 PM when the true Arctic boundary closes in on the Northeast.  Here is the projected surface map as of 1 PM tomorrow.
WPC Surface Fronts/Precipitation Thursday 1 PM 
High temps tomorrow don't climb much from the overnight minimums.  There is a strong chance the low for Thursday occurs at 1159 PM tomorrow night.  The max temp will go into the books as 20-25 tomorrow even if temperatures reach that value before noon time.  Here are the 1 PM temps, 10 PM temps, and 7 AM Friday temps.
18z NAM hires 3 KM temps Thursday 1 PM (Image Weatherbell)
18z NAM hires 3 KM temps Thursday 10 PM (image Weatherbell)
18z NAM hires 3 km temps Friday 7 AM (image Weatherbell)
Most importantly here are the wind chills for 7 AM Friday.  Schools might have to be delayed as kids standing at a bus stop in these temperatures is insane.  If you are one of the people who think we have gone soft then feel free to stand outside for 15 minutes tomorrow AM.  If you can congratulations you are stronger than a school aged child.
18z NAM hires 3 km wind chill temps Friday 7 AM (Image Weatherbell)
Temperatures will moderate slightly on Friday but max temps will only be between 10-20 degrees.  Then we will turn our attention to a snow threat on Saturday.  Snow will begin after midnight as the low seen below in Kansas cuts northeast.
WPC Surface Fronts/Precipitation Friday 7 PM 
The low is riding along the cold/warm boundary as it crosses the US.  One might think that because it is so cold tomorrow and Friday it has to be all snow on Saturday.  Well that is not how it works.  The cold will make the beginning of the storm all snow and it will probably snow harder and further south and east Sat AM then Monday AM's event.  Warmth will surge in later Saturday into Sunday.  In Southern New England we need storms to move south and east of Nantucket to get big snows.  When storms cut west they bring the warmth with them.  Think of the counter clockwise flow around a low.  If that low is to the west our wind is out of the south.


I am putting together some stats to put the December cold in perspective.  I will post that tomorrow.

-Zack Green

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