These cloudy skies should clear out later today with passage of a cold front. And, with a clear view of space tonight, temperatures will drop. And that, forecasters say, could mean at least patchy frost along the northern tier of counties in Maryland, especially if the winds calm, too. Clear skies, still air, spell frost when temperatures get into the 30s.

We won't be quite that cold in the city or near the bay. The forecast for BWI calls for a partly sunny skies today, with a high near 72. As skies clear, we could drop into the low 40s overnight. But it will be colder - in the 30s - to the north and west of the cities by early morning Tuesday. Westminster's forecast shows a low of 37 tonight. Ditto for Parkton, in northern Baltimore County.

Frost advisories are already posted for tonight across southern Pennsylvania, with freeze warnings in the northern half of the Keystone State. State College could see 35 tonight. Bradford could touch 30.

Skies should remain sunny through Wednesday. But then the high pressure moves out to sea, and we get into warmer, wetter flow of air from the south. The next storm system arrives from the west with increasing clouds on Wednesday, and chances for showers from Thursday evening through Saturday.

After a cool day Tuesday - in the mid-60s - daytime highs will stick near 70 for the rest of the week. Nights will warm back into the 50s as the week progresses.