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Posted at 11:30 AM ET, 10/21/2010

NWS & AccuWeather: Low chance for big snows

Unlikely Snowmageddon repeat for D.C. this winter

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The National Weather Service (NWS) and AccuWeather released their winter outlooks this morning and both agree the odds are strongly stacked against a historically snowy winter in the D.C. metro region.

"I'm not a betting man, but I wouldn't be betting for a very snowy winter [in Washington]," said NWS's Mike Halpert, deputy director of the Climate Prediction Center (CPC).

Halpert and CPC expect the development of a strong La Nina - perhaps in the top five on record -- favoring storm tracks west of the mid-Atlantic across the Tennessee and Ohio Valleys. That kind of storm track often brings a wintry mix of precipitation to the metro region.

Indeed AccuWeather also forecasts La Nina to strengthen, favoring "harsh conditions across the northern tier of the United States and drier-than-normal conditions throughout the southern tier" leaving the metro region near or just south of the "wintry mess" battle zone.

Though AccuWeather expects less snow in the region overall, AccuWeather chief long-range forecaster Joe Bastardi anticipates winter may begin with a bang for much of the East.

"It wouldn't be surprising if at the end of the December much of the eastern U.S. was similar to what it was last December," said Bastardi.

Of course, last December the D.C. area experienced "Snowpocalypse", its greatest December snow event on record (16.4" fell at Reagan National Airport). But Bastardi - presumably recognizing that - then said "I don't think quite as much snowfall."

For the winter as a whole, AccuWeather predicts above average temperatures for the region and average precipitation. The NWS outlook for our region is pretty similar placing us in the transition zone between stormy weather to our northwest and warm/dry weather to our south and southwest.

Both the current and forecast strength of La Nina increases NWS's confidence about the likelihood of the overall set up and that it will persist through the winter. Although its seasonal outlooks demonstrate skill (better than a random guess) only about half the time, predictability and skill increase during strong La Nina and El Nino events.

Historically, the tell tale signature of strong La Ninas has been warm, dry conditions across the deep South, cold/stormy conditions in the Pacific Northwest, and cold weather in the Northern Plains. Not surprisingly, both AccuWeather and NWS are forecasting these features.

NWS's Halpert cautioned that the Mid-Atlantic and Northeast are "always tricky areas" to forecast because the North Atlantic Oscillation (NAO) - a weather pattern in which snow chances can be reduced or elevated when cold air either remains locked in the Arctic or spills southward - can unpredictably change numerous times during the winter. In 2009-2010, the NAO was in its negative phase, a favorable state for snow, most of the winter. Not to mention, El Nino pumped a steady supply of deep moisture over the region - unlikely to be present this winter.

Capital Weather Gang's detailed winter outlook for the region will be issued around November 1.

By  |  11:30 AM ET, 10/21/2010

Categories:  Winter Storms

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