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    Final Days of Fall Largely Cold

    12/09/2013, 6:52:08 AM

    Monday, 11:45 A.M.

    The calendar tells me it is still officially "fall" for 12 more days, but the weather is clearly proving otherwise! The storm that came through the East to end last week left behind a carpet of cold, dense air that was quickly overrun on Sunday by the approach of a weaker and somewhat disorganized storm. And even though we ended up with one low center up in Michigan, and a second one off the mid-Atlantic coast, there was enough warm advection taking place that it forced moisture up and over the cold air, resulting in a band of snow that came down very hard for a time yesterday in parts of the mid-Atlantic. If you watched any of the football games from Washington, D.C., to Baltimore, to Philadelphia, you saw the results of that snowfall, especially in Philadelphia.

    The two lows are now well off the East Coast, and well north of the Great Lakes, and the cold front attached to the western system is moving across western New York and western Pennsylvania at this hour. It will move quickly off the Northeast coast this afternoon and early tonight, pulling colder air back in from the north and west.

    As that is happening, an upper-level disturbance moving out of the southern Rockies into the southern Plains will start to pull moisture right back in from the Gulf of Mexico, causing rain to break out across parts of the South and up into the Tennessee Valley and the southern mid-Atlantic. The 12z Dec. 9 NAM 500 mb forecast for this evening:

    As this moisture reaches the advancing colder air advancing in behind the cold front, the rain will change to snow, and there's the potential for a half of a foot of snow or more in some areas of the central Appalachians to southern New England from late tonight into tomorrow as this upper-level feature races off to the east. By late tomorrow, all of the snow will be done followed by rapid clearing from west to east. Here's the latest projected snowfall from this event:

    Again, someone within the 3-6 inch band could well pick up even more than 6 inches.

    Once this feature is gone, the bitter arctic that has frozen the rest of the country will invade the East, thought not to the extent it has plunged the Rockies into the ice box! Look at some of the temperatures and associated departures in Montana! Havre had lows of -38, -39 and -34 Friday through Sunday, respectively, with the first eight days of the month now averaging a whopping 25 below normal - and that includes Dec. 1 and 2 that were 17 and 2 above average, respectively! Take those two days out, and the past six days have been 36 below average!

    Look at the projected anomalies for Wednesday, when the core of the cold air moves through the Lakes into the Northeast and mid-Atlantic states:

    A lot of the country now has at least a minimal snow cover, too:

    This will keep the air mass very cold, and is likely to mean air temperatures ending up a little lower than model projections.

    Lurking on the horizon is the threat of another storm this weekend. It will begin Friday with rain breaking out from central and East Texas and Louisiana up into Missouri. It will then spread eastward across the Mississippi Valley into the Deep South and the Tennessee Valley Friday night, with some snow and ice in the Ohio Valley.

    The exact track of this storm is far from etched in stone, but suffice it to say it will be a disruptive storm, especially from the Ohio Valley and Great Lakes to parts of the mid-Atlantic and New England. Then, once that storm passes, guess what? Yep, another shot of cold air plunging into the Midwest and down the Mississippi Valley, then through the Lakes and Ohio Valley to the East Coast later in the weekend into the beginning of next week.

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

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