The Nation's Weather 12.18.09

By WEATHER UNDERGROUND (AP)

A potent storm system was forecast to deepen throughout Friday as it moved from the Gulf of Mexico across the Florida Peninsula and began its trek up the East Coast.

The storm was expected to drop heavy rain along the Gulf Coast at the start of the day, but by noon Eastern time, it would begin to track northeastward, heading for the Carolinas. Once in the Atlantic, the storm was expected to feed off the abundant warm water of the Gulf Stream current and begin a process of rapid intensification. By nightfall snow was forecast in the southern Appalachian Mountains, moving north to around the Pennsylvania border.

At the coast, rain was expected to make its way north to the Mid-Atlantic. Overnight the storm was expected to drop significant snow throughout the Mid-Atlantic — lasting through the weekend — and some locations were forecast to see very heavy snowfall totals by the time the weather cleared on Sunday.

Generally calm weather was forecast for the Plains Friday, with light overcast throughout the Northern Tier states, and a few showers and snow showers throughout the Dakotas.

Along the Pacific Coast, a Pacific storm was to push into the Northwest, bringing rain to the coast and snow to the higher elevations.

Temperatures in the Lower 48 states Thursday ranged from a low of -23 degrees at Mt. Washington, N.H. to a high of 84 degrees at Marathon, Fla.