The Nation's Weather 10.12.09

By WEATHER UNDERGROUND (AP)

Most of the nation will experience a chilly Columbus Day with areas of scattered, mixed precipitation throughout Monday afternoon. A very cold high pressure area in the northern Midwest will advance eastward, spreading into the Northeast during the day.

Early morning temperatures near freezing around the Northeast raised the possibility of frost warnings. Daytime temperatures from the Rockies through the Northeast are expected to remain unseasonably cold.

As the cold air mass chills much of the nation, the Plains can expect a wintry mix of precipitation. Light snowfall will continue to blanket higher elevations of the Rockies and the northern Plains, while scattered rain showers are expected in the central and southern Plains.

Meanwhile, a frontal boundary along the Gulf Coast will kick up showers and thunderstorms from western Texas through the Southeast. The most significant precipitation is expected in the Tennessee Valley and the southern Mid-Atlantic region. Persistent rains also raised the possibility of local flash flooding in some areas of the Southeast.

Elsewhere, coastal states in the West will begin to see the early effects of an approaching Pacific storm system. Increasing, moist flow may yield to cool afternoon showers in northern California, while chilly and breezy weather is expected in the Pacific Northwest. Wet weather in California will become more widespread in the evening.

Temperatures in the lower 48 states Sunday ranged from -10 degrees at Polebridge, Mont. to a high of 95 degrees at Punta Gorda, Fla.