Winter Storm Boreas, so named by the Weather Channel, is the product of atmospheric low pressure interacting with a deep trough of Arctic air. Late last week, as the Arctic front was plunging southward across the Rocky Mountains and Great Plains, a center of low pressure had developed over the Desert Southwest. Since, in the Northern Hemisphere, winds move counterclockwise around a low, this storm swept Pacific moisture northward; forced to rise above the dense Arctic air, the humid flow dropped heavy snow across the Colorado Plateau and southern Rockies.
Over the weekend, as it moved eastward below the Arctic cold front, Boreas drew in moisture from the Gulf of Mexico, producing bands of snow, sleet, freezing rain and thunderstorms across the Southern Plains; as of this evening, the storm is centered off the northern Gulf Coast, poised to move up the Atlantic Seaboard. At present, the Arctic front has stalled along the Appalachian Chain; as Boreas moves NNE, it will pull in Atlantic moisture, drenching areas east of the front with heavy rain and dumping snow or icy precipitation across the Appalachians and interior New England.
A battle between high pressure off the Atlantic Coast and high pressure behind the cold front will determine where the freeze line sets up in the Northeast. As of now, the major urban corridor (from Washington to Boston) is expected to be in the warmer rain zone; should the front shift eastward, however, Boreas might produce windblown snow or freezing rain across that Metroplex, creating havoc for Thanksgiving Holiday travelers. By late in the week, the storm is forecast to move into the Canadian Maritimes, completing its broad sweep along the edge of our Continent.
