The Nation's Weather 12.09.09

By WEATHER UNDERGROUND (AP)

The winter storm over the Central and Eastern U.S. was expected to amplify on Wednesday.

As the system pushed eastward into the Mississippi River Valley, it was forecast to scoop up a minor trough lingering over the Gulf states and strengthen as it obtained additional moisture. The system was expected to create a double frontal boundary, with one strong cold front followed closely by a second, that could sweep from the Central Plains, over the Mississippi Valley and approach the East Coast.

The system was expected to extend well northward into the Great Lakes, where it could continue bringing periods of heavy snowfall. Winter weather and blizzard advisories were to remain in effect over the Midwest as snowfall were expected to vary between 1 and 2 inches per hour. Wind gusts of up to 29 mph were expected over the Upper and Mid-Mississippi Valley.

The Upper Midwest and Great Lakes region could see up to 3 inches of new snow, while New England and the Northeast were expected to see increasing snowfall with totals less than a half of an inch.

To the South, above-freezing temperatures could allow for periods of heavy rain associated with late season thunderstorm development. A messy combination of sleet and frozen rain was expected between the Tennessee and Ohio valleys. Dangerous roadways were expected.

Behind the storm system, cold air was forecast to continue pouring in from Canada. It could allow for extremely cold temperatures over the Northern and Central Plains with wind chills that allow for below-zero temperatures.

Breezy conditions were anticipated over most of the Rockies and Central U.S. Further West, a trough of low pressure off the West Cost was expected to push moisture over California and allow for another rainy and cool day. Highs were expected to remain in the 40s and 50s across the West Coast.

On Tuesday, temperatures in the Lower 48 states ranged from a low of -34 degrees at Havre, Mont. to a high of 89 degrees at Punta Gorda, Fla.