A moisture-laden cold front moving in from the Midwest was expected to hit the Washington area early this morning, bringing rain, strong winds and temperatures plunging to below freezing tonight.

Forecasters predicted rain for the Washington area this morning, possibly changing to snow before ending around noon, with today's high temperatures ranging from the low- to mid-40s. Winds will become northwesterly today, increasing to 25- to 30-miles-per-hour with stronger gusts.

The weather service predicted that temperatures tonight would drop into the 20s. Forecasters said snow could accumulate up to four inches in parts of far western Maryland.

A spokesman for the National Weather Service said the abrupt change in weather was caused by a shift in the jet stream, a strong current of air that usually travels east or west along the Canadian border, but which has dropped south and pushed cold Canadian air farther south.

"It's sort of late for this kind of weather but it is not out of the ordinary," said National Weather Service specialist Walter Green. He said that on average the last day of freezing temperatures is March 29 and that the latest day on record for below freezing temperatures in Washington is April 16.