A DISTINCTIVELY SOUTHERN PLACE MAY 2017

Irving Berlin’s hit song “White Christmas” has forever romanticized dreams of a pristine display of snow Dec. 25. In the high mountains and northernmost parts of the nation, the dream reliably becomes reality. But in the South, Christmas snow remains a dream most of the time.

But each year, a white Christmas surprise usually delights some areas unaccustomed to it. How much this happens and where depends on the availability of cold air and the exact arrangement of weather systems.

This year, we think we’ll have the necessary influx of cold to boost the chances of above-normal coverage of snow across the nation on Christmas Day. The challenge is figuring out where the cold will focus and  then where any storminess to supply snow may track.

We are intensely tracking a surge of Arctic air expected to spill into the Lower 48 in the days leading up to Christmas. Some models steer the cold west while others steer it more to the east. Wherever the cold goes, so too will the best potential for a white Christmas.

Models differ on how far east cold air will penetrate Christmas morning and where it might be stormy. Blue-green-purple shades indicate colder than normal air, while yellow-orange-red shades indicate warmer than normal air. (WeatherBell.com adapted by CWG)

Capital Weather Gang contributor Matt Rogers, who specializes in long-range forecasting, said the models are jumping all around with their projections. “It’s a real mess right now,” he said. “If you believe the American model, the chances are highest for more snow in the East. If you believe the European, it’s more the West. It’s really tricky.”

A group of simulations from the European model suggests much of the western Plains through the Rockies has better than a 50-50 chance of at least an inch of snow on the ground Christmas morning. Chances plunge below 10 percent south of a line from Missouri to Virginia where the model favors much warmer than normal conditions.

European model ensemble probability of at least one inch of snow on the ground Christmas morning. (WeatherBell.com)

The American model shows a little more promise for snow in places such as the Tennessee Valley and Mid-Atlantic, which normally have very low chances.

[Washington’s white Christmas odds are low as usual this year, but there’s a glimmer of hope]

Over the next week, the Christmas forecast will come into better focus.

Historically, according to data crunched by the National Oceanic and Atmospheric Administration (illustrated in the map below), these are the locations that are just about locks to see treetops glisten Christmas morning:

  • Northern Minnesota, northern Wisconsin and the Upper Peninsula of Michigan
  • Northern Maine
  • High elevations of the West
  • High elevations of the Northeast
Historic chances of a white Christmas across the Lower 48 states. (NOAA)

At least 50-50 odds for snow extend south to around central South Dakota, northern Iowa, southern Wisconsin, central Michigan and the interior low elevations of the Northeast.

The places that are most accustomed to having snow on the ground Dec. 25 already have a hefty blanket as of Dec. 14. Much of the Dakotas the western Montana are snow-free, but models suggest these places have a good chance to see snow in the next 10 days with the expected Arctic air invasion.

Snow cover as of Dec. 14. (NOAA)

 

Source : https://www.washingtonpost.com/news/capital-weather-gang/wp/2017/12/14/more-places-than-normal-may-have-a-white-christmas-this-year-across-lower-48/?tid=pm_local_pop_b

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