The Nation's Weather 10.17.09

By WEATHER UNDERGROUND (AP)

A developing low pressure trough will sweep the eastern third of the U.S. and provide an early glimpse of wintry weather.

Stormy weather on the trough's eastern edge is expected to move up the Eastern seaboard, scattering moderate to heavy precipitation through the Mid-Atlantic states and coastal New England. This activity will continue into Sunday as the storm moves up the coast with a chance of flooding in some areas of the Mid-Atlantic.

The trough will allow seasonally cold air to plunge into the eastern third of the country down to the Southeast. Cold air will mean some snow for areas of the Northeast and greatly dampened daytime high temperatures for much of the eastern U.S.

In much of the West, a high pressure ridge again heralds widespread dry conditions. Seasonally warm conditions will also creep into the Southwest and Southern California.

Farther to the north, a Pacific low pressure system will slam into the Northwest, with rain expected in western Washington and Oregon.

The Northeast's temperatures will rise into the 30s and 40s, while the Southeast will see temperatures in the 50s and 60s. The Upper Midwest will rise into the 40s, while the Southwest will see temperatures in the 80s, 90s, and some 100s.

Temperatures in the Lower 48 states Friday ranged from a low of 17 degrees at Berlin, N.H., to a high of 103 degrees at Thermal, Calif.