Looking Toward December: warm to start, but it won’t last

The rest of November looks warmer than ‘normal’ around Alabama and Tennessee.  We started this month very warm (+11ºF relative to ‘average’ for the first seven days), but temperatures cooled significantly after that.  In fact, the past seventeen days have been below average temperature-wise: -2.9ºF relative to the 30-year climatological ‘normal.’

That climatological normal drops quickly this time of year.  We go from a daily average temperature of 59ºF Sunday to an average of 57.8ºF by next Thursday; that’s a steep drop over a short time.

The weather pattern sets us up for more of the same kind of coolish/mildish weather we’ve had over the past few days going forward through next week: a few warmer days, a few cooler days, mostly dry, and nothing extreme.

So when does that normally-wild, one-extreme-to-the-other kind of November and December weather crank up?

From the looks of things, it could happen within the next two to three weeks.

November will end on a slightly warm note (relative to normal), and December begins with that same pattern: a zonal, west-to-east flow across the Lower 48 keeping the bitterly cold air locked up north for now.  That lasts through about December 5th; then things start changing.

A deeper trough (big ‘dip’ southward) in the jet stream over the eastern United States develops after the 5th; there’s a good chance it stays around through Christmas, and that should make this December a fairly cold one around this part of the country!

Could there be some snow?  The ECMWF EPS Weekly long-range guidance shows it getting close, but there’s really no way to be certain.

EPS ‘control’ 5-day snowfall through Dec. 22nd

Will there be severe weather?  A flip like this rarely comes without some rain and storms; however, just like snow potential, it’s a wait-and-see deal.

This European guidance has been pretty hard-nosed in projecting two substantial cold waves in December; it’s shown it as a possibility on almost every ‘weekly’ update this month: one around the 11th and another just before Christmas.

Are we talking 1989 kind of cold?  Probably not to that level, but it certainly could be one of the coldest Decembers this decade.  The last time we had a colder-than-average December was 2010; that December’s monthly average was 38.2ºF, and the long-term average is 43.9ºF.

We did have a white Christmas in 2010, so in the immortal meme from Dumb and Dumber

Need some specifics about the weekend or next week? They’re always online at WHNT.com/Weather and in the “Daily Forecast” section on Live Alert 19!

-Jason
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