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Posted at 9:30 AM ET, 11/10/2010

Long range look: Pre-Thanksgiving cold snap?

By Jason Samenow

* Sun & 60 again: Full Forecast | Polls: Global warming manmade? *

cpc-8-14-110910.jpg
8-14 day outlook for temperatures from NOAA's Climate Prediction Center. Below average temperatures probably invade the center part of the country and could then eventually head east.

Our friends at AccuWeather are advertising the season's first significant Arctic outbreak in the days leading up to Thanksgiving. They write:

It appears building cold air over Siberia will soon move eastward through the Arctic over the next week or so, then drive southward through North America during week three of the month.

The potential cold snap shows up in several weather forecasting models. Indeed NOAA's Climate Prediction Center writes in its 8-14 day outlook: "The temperature tools indicate good consensus for greater chances for below average temperatures across most of the continental U.S."

It looks to be an Arctic outbreak fairly characteristic of La Nina with the northern Plains feeling the brunt of it in about 8-10 days, with the cold air moderating somewhat by the time it reaches the East Coast perhaps around the weekend or Monday before Thanksgiving.

Before the cold air arrives, there's likely to be a warm surge followed by a period of rain. I imagine the storm will track to D.C.'s west with heavier rain/storms in the Ohio Valley and snow on the backside to the north and west.

How cold will it be in the D.C. metro region? It's very difficult to project the intensity of the cold air outbreak this far out. But if I had to guess, I'd say it might drop temperatures 10 degrees below average. That would mean blustery highs in the mid-40s or so in the days prior to Thanksgiving. Stay tuned...

[Post script: CWG's Steve Tracton wisely notes that forecast details outside the short-range (3-5 days or so) are not particularly reliable and have little skill beyond about a week (read about declining predictability with time here). So while there are signals that the pattern will trend cooler, take the detailed projections about the evolution of day-to-day weather features with a big grain of salt]

By Jason Samenow  | November 10, 2010; 9:30 AM ET
Categories:  Latest, U.S. Weather  
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Comments

Hey Jason, we are looking at a possible two-pronged push of Polar air. The first one would hit DC for the weekend prior to Thanksgiving (Nov 20ish) and the second one would arrive maybe right during the Thanksgiving holiday weekend. There are definitely certain pattern indicators lining up to suggest a colder North American pattern for the 2nd half of Nov.

Posted by: MattRogers1 | November 10, 2010 9:37 AM | Report abuse

Who has readied the winter insulation at home? I need to install more.. and check my caulking!

Posted by: Camden-CapitalWeatherGang | November 10, 2010 9:59 AM | Report abuse

Time to turn off and drain the water lines to the outside.

The weekend before Thanksgiving I'll be in the mountains near Front Royal. Guess I'll need the sub-freezing weather gear.

Posted by: wiredog | November 10, 2010 10:45 AM | Report abuse

How far south will these cold air masses reach? I'll be in Orlando the week of Thanksgiving- might be sweater weather that week? Or should I pack the bikinis?

Posted by: Snowlover2 | November 10, 2010 10:55 AM | Report abuse

Good! I bought a cord of wood three weeks ago and want to find an excuse to start using it.

Posted by: novatom | November 10, 2010 10:59 AM | Report abuse

No chance of a Snowvemberpocalypse?

Posted by: Langway4Eva | November 10, 2010 11:09 AM | Report abuse

Be aware that the forecasts cited are for the days (1 week average) leading up to, but not including Turkey day

The CPC prediction shown is probabilistic with the dark blue indicating a 45% chance of below normal temperatures ==> 55% chance of near or above normal.

I do not think it wise to extrapolate a forecast, which already is characterized with considerable uncertainty, through the period encompassing Thanksgiving. And this applies especially to the no skill "near normal" encompassing DC.

Even if the weekly average turns out to be cold, that does not necessarily mean that any given day during that week, including Turkey day, might be warm.

Posted by: SteveT-CapitalWeatherGang | November 10, 2010 11:10 AM | Report abuse

If we can stay dry, colder is fine with me. Some insects are daring to reappear in this week's sunshine and mild temps.

I'm already resigned to Allegheny Power ultimately bankrupting me, so no biggie....

Posted by: tinkerbelle | November 10, 2010 12:12 PM | Report abuse

AccuWeather's Jesse Ferrell has a good discussion about how cold the model output suggests it might get: http://www.accuweather.com/blogs/weathermatrix/story/41413/models-on-how-cold-late-november-will-be.asp

Posted by: Jason-CapitalWeatherGang | November 10, 2010 12:31 PM | Report abuse

@Snowlover2

It's too sign to speculate as to whether the cold air will penetrate into Florida.

Posted by: Jason-CapitalWeatherGang | November 10, 2010 12:32 PM | Report abuse

Leave it to accuweather to tout a prediction for snowcover in Alabama in November.

Posted by: ah___ | November 10, 2010 12:46 PM | Report abuse

whoops - Mississippi (and a little bit of Alabama).

Posted by: ah___ | November 10, 2010 12:47 PM | Report abuse

ANYONE who considers it meaningful to give even the very slightest bit of attention and credence to a 384 hour (16 day) forecast for a particular day from any model or ensemble is living irresponsibly in some far off fantasy land.

Posted by: SteveT-CapitalWeatherGang | November 10, 2010 12:58 PM | Report abuse

Interesting...the temperature maps don't give US the brunt of the cold weather.

What we do seem to get isn't shown here but is rather evident on precipitation maps for the same period. This explains my note to TominMichiganPark in my separate post...he will probably enjoy next week's cloudy raw rains, though I probably won't...more SAD, barring a drop in temperatures below 32 and a change to ice/snow.

Posted by: Bombo47jea | November 10, 2010 1:20 PM | Report abuse

Thanks for the response, Jason! I figured it is too early to tell- but interesting to watch!

Posted by: Snowlover2 | November 10, 2010 9:36 PM | Report abuse

The comments to this entry are closed.

 
 
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