By Alex Sosnowski
STATE COLLEGE — It could be a white Christmas after all in Pennsylvania, New Jersey, New York, New England and other areas across the nation.
Despite the fact that 2012 likely to finish up as the warmest year since at least 1950 in the United States, enough cold air is on the move to spread snow to locations that haven’t seen that much over the past couple of years for Christmas.
The most recent storm, a major blizzard, put down a swath of heavy snow from Colorado to Michigan, and it is not done yet.
Part of a new storm, currently north of Hawaii, has a chance of tracking in just the right manner to spread a swath of snow beginning from the central Appalachians to the northern mid-Atlantic coast and southern New England spanning Christmas Eve into Christmas Day.
In the most likely scenario, the storm is not expected to become very strong, but rain showers and mild air would still be drawn northward into the Tennessee and Ohio valleys, the Carolinas, the Virginias, Maryland, Delaware and southern New Jersey.
As the storm glides toward the Atlantic coast, a change to snow is possible from the central Appalachians to areas farther east near the Mason-Dixon Line.
However, even with this portrayal, there is a chance of a period of accumulating snow from Harrisburg and Scranton, Pa., to Hartford, Conn., and Boston, where the air would stay cold enough on the front side, middle and tail end of the storm. In the swath from northern Maryland, Philadelphia and northern Delaware to central New Jersey, New York City and Long Island, part rain and part snow are most likely.
There is a remote possibility that the snow will mix in near the end of the storm system in Washington, D.C., and Baltimore, Md. Snow could also be flung as far north as Albany, N.Y., and Portland, Maine.
If the storm were to grab sufficient moisture, accumulations would shift from a scenario bringing a coating to an inch or two to a scenario producing a half a foot of snow in some locations near and north of the Mason-Dixon Line to near the I-95 corridor in southern New England.
Areas from the Alleghenies to the Poconos, Catskills and Berkshires have the greatest potential to get several inches of snow from such a storm.
If the storm were to remain very weak, only rain showers and snowflakes would affect the mid-Atlantic with no significant accumulation.
In the wake of the Christmas snow potential in the Northeast, a second and larger storm is in the making beginning Christmas Eve and Christmas Day in the West.
That storm would also become much stronger than the East Coast system and will unload heavy snow from the Sierra Nevada to the Wasatch and central and southern Rockies spanning Christmas Eve and Christmas Day.
By the day after Christmas, as many seek to return their unwanted gifts or head home after visiting friends and family, the second storm is forecast to evolve into a monster over the middle and lower Mississippi Valley.
By then the second storm will have windswept snow on its northwest flank over part of the southern Plains and the Ohio Valley states, drenching rain to its east into the southern Appalachians and severe weather in the South.
That second storm is forecast to set its sights on the Northeast Wednesday night and Thursday with strong wind, areas of rain, thunderstorms and perhaps a blizzard on its northwest flank.
The exact track of the storms next week will determine where the rain/snow line sets up.
Alex Sosnowski is a senior expert meteorologist at Accuweather, based in State College