Monday, December 21, 2015

Record Warmth for Christmas Eve?

 While some may be dreaming of a White Christmas it is not in the cards for much of the Eastern United States this year (see Heatmiser's revenge).   An active weather pattern will lead to showers at times and the potential for record high temperatures on Christmas Eve.  The rain showers are good as it is still very dry in Southern New England.  Christmas day looks to be mild and dry..

General Overview
The 4 PM surface analysis shows southwest flow in New England with tropical origins. 
WPC surface analysis 4 PM (image NOAA/NCEP)
 The upper air pattern is mostly zonal across the United States with several embedded disturbances
18z NAM 500 mb vort 4 PM (image NCEP)
The feature in the Great Lakes will move toward New England tonight and help to keep the warm front in North Central New England.  With this will come some rain showers tomorrow mainly after 7 AM.  The coverage will increase mid morning through mid afternoon.  Expect high temperatures in the mid 50's in Southeastern New England tomorrow.  It will be cooler in Western MA/CT.  By tomorrow evening the surface map shows the warm front well into Northern New England
WPC Surface forecast/weather type Tuesday 7 PM
Upper level flow goes more to the west Wednesday morning so we are looking at a chilly start.  Temperatures will likely be in the low 40's around 10 AM.  With the potential for some showers this may feel pretty miserable.
18z NAM hires 2 m temps 10 am Wed (image Weatherbell)
That said high temperatures on Wednesday are likely to occur closer to midnight as another upper level disturbance pushes to the west and advects a potentially record setting air mass into Southern New England
18z NAM 500 mb vort Wednesday 10 PM (image NCEP)
This pattern is highly amplified in the east with tropical connections.  The amount of moisture in the atmosphere is rare for December
18z NAM Hires precipitable water Thursday 1 AM (image Weatherbell)
In English this means temperatures in Southern New England on Christmas Eve will be in the mid to upper 60s and as NWS Boston points out with any sunshine somewhere could hit 70.  The limited daylight makes this a tall order but it could happen between 1-3 PM.  Total precipitation in the next 3 days is 1-3" across the region.
WPC Days 1-3 precipitation forecast through 7 PM Thursday
Based off the current National Weather Service forecast for Thursday nearly the entire region will set new record highs.  Via Dr. Ryan Maue who runs the weatherbell models records are based on long-period stations from the Threaded Extremes historical station time series Dataset . Forecasts are to nearest degree to account for rounding and ties.
NWS temperture forecast for Thursday.  White circle indicated new max high temp record (image Weatherbell)
I expect mid to upper 50's on Christmas Day.  That's all for now- Merry Christmas I will post some 2015 review items over the next 10 days.

-Zack Green



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