Winter Storm Watches and Warnings from North Carolina to Maine, up to 10 inches expected in the Appalachian mountains. More on the atmospheric "bomb" below...
*The Hurricane Irene comparison? On August 26, 2011 Irene reached a central pressure of 942 millibars. Since Tuesday, computer models have shown that this storm will rapidly deepen in the overnight hours. The anticipated drop in central pressure is projected to be over 24 millibars in a 24 hour period. This is the unofficial criteria for an "atmospheric bomb" or "bombogenesis" which is a meteorological slang along the eastern seaboard. The October 2011 Northeast U.S. snowstorm is the most recent example of this phenomena.
7:45 AM EST 12/7/11
MID-ATLANTIC STORM UPDATE | Overnight, computer models and forecasters alike came to a consensus that the influence of powerful upper level low is going to fire off a rapidly deepening coastal "bomb" at the surface. By tonight, an explosively developing storm along the Virginia Capes will begin to move northeastward. As a result, areas up to 200 miles west of the storm may be impacted by "dynamical cooling" which will be responsible for generating snow in this early season event, even into the major metro areas of Baltimore and Washington as well as much of the Central Appalachians by tonight.
Evidence of the National Weather Service's concern for this potential
are the surprisingly widespread Winter Weather Advisories, Watches and now even Warnings from North Carolina to Maine. Current advisories
TIMING & IMPACTS Precipitation has already entered over most of the region with rain possibly heavy at times today. A change over to snow is expected from west to east across the region tonight, beginning around 3 pm in the central Appalachians. Rain in the I-81 corridor is expected to change over to snow around 8 pm and progressing north and east through the overnight hours.
The 95 corridor and adjacent counties in Maryland may start to see snowflakes after 1 am then a brief period of snow is possible over I-95 from Wilmington, DE to NYC. Precipitation is expected to depart from southwest to northeast starting near 3 am in central MD, with the back end of precipitation departing the interior Mid-Atlantic by mid morning and coastal areas by noon.
IMPACTS TO 95 CORRIDOR (SOUTHEAST PA -- DC METRO):
Influence of heavy rainfall prior and lack of substantially cold air drives our low projections for the I-95 corridor. For the most part, right along I-95 and to the south and east, we expect a coating to an inch. To the north and west of I-95, accumulations will likely remain from 1-2 inches. Once you get north and west of northern VA, Frederick, MD, Westminster, MD, and Lancaster, PA, accumulations are expected to range from 2-4 inches.
IMPACTS TO 81 CORRIDOR (CENTRAL PA -- CENTRAL VA) :
The I-81 corridor and just to the north is expected to receive some accumulating snow, likely 2-4 inches with some isolated spots to 6 inches from northern VA through Hagerstown, MD, Harrisburg, PA. North of Harrisburg, the region may see a general 3-6 inches, but higher elevations could see accumulations of approaching 10 inches. Other than that, highest amounts are expected in the mountains of West Virginia, northern Virginia, and western Maryland with a general 3-6 inches expected in that area along with isolated amounts of up to 8 inches.