Extended Forecast

First off I hope everyone is enjoying there Thanksgiving weekend.  A very nice Saturday is shaping up across Southern New England.  High pressure is just off of the North Carolina coast and is responsible for the unseasonably warm November weather.  The run of above average weather will continue until the North Atlantic Oscillation reverts to its negative phase.  The University of Columbia has made some nice graphics illustrating the effects of the NAO.
NAO Positive Phase
When the NAO is positive, the pressure gradient between Greenland and the Azores Islands is greater so storms are stronger; the Pressure Gradient Force is on of the most important forces in Atmospheric Science.
NAO Negative Phase
In the Negative Phase Greenland warms up while the East Coast is prone to more snowy outbreaks.  These graphics are slightly outdated and slightly incorrect, but it captures the general idea of the NAO.

Check out Columbia's webpage here.

For virtually all of November the NAO has been positive and it looks like it will continue into early December.  The models are not great at pattern recognition; they often break down patterns too quickly.  They have been hinting at a flip to the negative phase, but this has yet to happen.  The longer the NAO is positive the warmer our weather will be.  Here is the Climate Prediction Center forecast through December 1 and beyond.  Given that the models wanted to change this pattern for several weeks now, I think winter is coming fast.

So with the big picture out of the way, time for the forecast.    Today's temperatures will soar into the lower 60's.  Tonight a backdoor cold front drops in from the Gulf of Maine and will increase the chances for fog in the area overnight.  The front will stall, then lift north as a warm front letting temperatures soar in the mid 60's tomorrow as well.  We may approach record values today and/or tomorrow.

Increasing cloud cover will allow for overnight lows to be in the upper 40's tomorrow evening.  Monday looks to be a decent day, there is a slight chance of a shower late in the day but it will be a mostly cloudy afternoon with highs near 60.  By Tuesday a system is going to lift out of the Southeast and head north.  It will pass to our west so there is no chance for snow but rain will approach by early evening.  The Northbridge-Nipmuc game looks to be ok, but the later playoff games may be impacted by rain.  A shift in the timing by 3 hours throws a wrench in this forecast so stay tuned.  Wednesday will start off as wet before drying and cooling down later in the afternoon.

The end of next week and the start of December looks to be average, with sunny skies and temperatures in the low 40's.  For the longer range here is my look for December...

These are from NOAA's Physical Science Division US Climate Division data maps.  While average temperatures across the analog years were in the 20-30 degree F range, that indicates to me a battle ground for rain and snow in the month.  Precipitation looks likely for December so it is going to be a battle to see if cold or warm wins out, especially in the Blackstone Valley.  Areas north of Worcester should be mainly snow.  


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