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Posted at 02:30 PM ET, 02/21/2012

Is winter over for most of the U.S.?

For places like D.C., Philly, New York, and obviously points farther south, winter may well be about done (not that it really got started). With a mainly mild and wet close to February, and longer-range models predicting mostly warmer-than-average weather during March, I don’t think odds of adding to the meager snow totals along the I-95 corridor are good.


Temperature anomalies expected Thursday from the GFS ensemble mean (Penn State)
That’s not to say winter is over for everyone in the country. Far from it. There are some places that are staring down some nasty cold before the turn of the month.

The highlight this week for the Central Plains and East will be the warmth. Another round of exceptionally mild air will develop in the middle of the country tomorrow, pushing high temperatures in places near Kansas City, for example, well into the 60s. That air will rush toward the east, sending 60s and 70s all the way from New York to the Carolinas on Thursday. Simply amazing.

By Friday, enough moisture will be in place east of the Appalachians for a rainy, and potentially stormy, end to the work week.

As a polar branch of the jet stream begins to dive southward toward the Intermountain West over the weekend, in association with significant upper-level ridging near the West Coast, a really cold shot of Canadian air … with anomalies more than 20°F below climatology … will spill into the Northern Plains. It will be downright frigid in Montana and in the Dakotas for some of the last days of the month, with highs there only into the single numbers on Sunday.


Forecast of the jet stream (outlined by the black arrow) for Monday. (ECMWF)

As shown in the image above, the northerly dip in the jet stream over the West curves into a southwesterly flow across the eastern third of the Lower 48. This should largely protect the East Coast from the mid-continent cold spell.

Perhaps the most interesting weather associated with this jet stream will occur in the transition zone (hatched area in the image above) between the really cold air in the Northern Plains and the mild air in the Southeast. Over the weekend, a strong low pressure system will develop in this region and likely give some locations in the Northern Plains and western Great Lakes a fierce little snowstorm, with strong winds and a dose of Canadian chill.

But as the upper trough in the West slowly moves eastward later next week, it will weaken and allow the cold air underneath it to modify significantly before it reaches the East Coast. We’ve seen this scenario unfold earlier in the season, where only slightly below-average temperatures last just a couple of days in the East as the remnants of a once powerhouse trough finally get there.

So there it is. With signs pointing to a warm March, many of us will soon celebrate the fact that we endured the darkest months of the year one more time. Unfortunately, this also means some of us will need to deal with a severe weather season that is showing signs of being quite productive.

By  |  02:30 PM ET, 02/21/2012

Categories:  Latest, U.S. Weather

 
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