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    Extreme Cold Exits, but Still Plenty of Chill to Go Around

    3/27/2014, 8:43:47 AM

    Thursday, 11:59 a.m.

    The snow hurricane that brought 83-mph winds and at least 9 inches of snow to Nantucket Island Wednesday has roared through eastern Canada overnight and this morning. Arctic air drilled southward behind the storm deep into the South and Southeast, and as high pressure moved into the East overnight, temperatures plummeted to record levels. New York's LaGuardia and JFK airports each dropped to 23, while nearby Newark, N.J., slipped to 22. Where records were not set, it was still well below average, with temperatures over the past 24 hours 15 to 20 degrees below normal.

    That arctic air is now in retreat as the surface high slips off the East coast. Southerly winds have been freshening overnight and this morning ahead of a storm over northern Kansas and southeastern Nebraska. Here's the 11 a.m. surface pressure analysis:

    This will behave as a more typical early spring storm, with the potential for severe weather ahead of the storm and snow on its northwest flank. With the storm heading for the northern Lower Peninsula of Michigan later tonight, then into southern Quebec later tomorrow, the snow that does fall will largely be contained to areas where you would typically anticipate seeing snow at the end of March. Here's the latest projected snowfall amounts:

    It's plenty cold in the Dakotas and northern Minnesota right now, and some of that colder air will slide southeastward tonight and tomorrow, but look at the upper-level flow behind the departing upper-level trough tomorrow evening:

    West-southwest winds aloft will eventually cause this low-level chilly air to come to a grinding halt after clearing New England, so that areas south of the Mason-Dixon Line will pretty much stay mild into Saturday as the next wave of low pressure develops. And you can see why it will form from that image above, as the ensuing upper-level trough is already crossing the Plains.

    There have been some differences amongst the modeling as to how this second storm behaves. Some models, such as the European model, have been slowing it down quite a bit and closing off an upper-level low over North Carolina and Virginia Sunday. In contrast, the GFS and NAM models are much more progressive, driving the storm off the New England coast Sunday morning. This would bring a much more swift end to the precipitation. Given how they had a better handle on this most recent storm, I tend to lean in their direction with the next one.

    As this storm moves from west to east, it will pull a little more cold air in from the north and northwest, and the chilly rain is likely to either mix with or change to snow from parts of Ohio into western and northern Pennsylvania and upstate New York later Saturday into Saturday night, then across northern New England Saturday night and Sunday morning. Look at the extent of the cold on Sunday, as projected by the 6z March 27 GFS ensemble 2-meter temperature anomalies:

    This is NOT the same kind of cold we've seen in recent weeks, but it is no surprise to see it that chilly behind the departing storm and attendant cold front. Furthermore, look at the intense cold north of the border! If this was last week, that cold air would be charging across the border and making a beeline to the Gulf Coast and the East Coast.

    However, we're in a new flow pattern now, one that is much more zonal. Look at the 0z GFS 500mb forecast for Sunday evening:

    The next upstream trough will come into the West Saturday night, pushing rain ahead of it through the Northwest and down into northern California. Rain and mountain snow will then expand into the northern Rockies, and by Sunday afternoon, low pressure will be reorganizing and deepening over the eastern Rockies and western Plains in a very similar fashion to what we've seen overnight and this morning in virtually the same area.

    Moisture will be somewhat limited with this storm on Monday, though there will be enough of it in the cold air north of the track of the storm for accumulating snow from northwestern Nebraska and South Dakota into northern Minnesota, while showers move across the Midwest and middle Mississippi Valley toward the Great Lakes and Ohio Valley. Severe weather appears to be unlikely with this event.

    Once again, cold air will be pulled southward to some extent behind the departing storm into the central Plains and across the Midwest into the northern Great Lakes, but it will probably stay mild from the Ohio River Valley on South. That means Monday will be rather nice in the East, and probably milder on Tuesday from southern New England and the mid-Atlantic states on south.

    Then ANOTHER storm will come along, a much stronger one, with more chilly air pouring across the Plains to the Appalachians, and then spilling over the mountains into the East late next week into next weekend.

    The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com


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