You knew this couldn't last. We've had three days in a row, now, with highs in the 60s. That hasn't happened here since last Nov. 8-10.

But sunny days in the 60s will give way this weekend to four days in the 50s, with rain. And, for the western counties, especially, the mild temperatures and rain will combine to melt down the snowpack that remains on the ground there. Forecasters say small stream and creeks will likely overflow their banks, and river flooding could follow.

The National Weather Service has already issued Flood Warnings for portions of West Virginia southwest of Maryland's Garrett County. There are Flood Watches up from Garrett east to Washington County, including the cities of Cumberland and Hagerstown, where as much as 4 inches of rain could fall through Saturday.

East of the mountains, there are Hazardous Weather Outlooks posted as far as Carroll, Howard and Montgomery counties.

UPDATE: 6 p.m.: Flood watches are now posted for all Maryland counties west of the bay, plus the Upper Eastern Shore

For Baltimore, the rain is forecast to begin late Thursday night into Friday, with more than an inch expected by early Saturday morning. The rain could be heavy at times late Friday and Saturday, with another two inches possible. Rain chances continue into Monday, so it appears the weekend will be a washout. But at least it's not snow. And our snow cover is gone, except for some lingering piles. So we won't have to add that water to the runoff. The rain will be quite enough, thank you.

Needless to say, though, we'll need to be on the lookout for wet basements, leaks through ice-damaged roofs and gutters, overflowing creeks and street flooding. And that can collapse roads, as this amazing video from Freeport, Maine demonstrates.

Never drive through flooded low spots. It's amazing how little water it takes to float a car and carry it downstream. I suspect we will be reading about water rescues, anyway, this weekend.

All this rain is approaching as a low-pressure system moves very slowly toward us out of the Midwest. The counter-clockwise flow around the low is drawing mild, wet air north from the Gulf and, eventually, the Atlantic.

The heaviest rain will arrive late Friday and Saturday. Here's a bit of this morning's forecast discussion from Sterling:

"ONE BATCH OF RAINFALL ONGOING FRIDAY MORNING MAY LIFT NORTH IN THE AFTERNOON...LEAVING CLOUDS AND DRIZZLE BUT ANOTHER MORE SIGNIFICANT AREA OF RAINFALL IS STILL ON TRACK TO AFFECT THE [FORECAST AREA] FRIDAY NIGHT AND SATURDAY. RAINFALL TOTALS OF 1 TO 3 INCHES...WITH POTENTIAL FOR HIGHER AMOUNTS IN UPSLOPE AREA...ARE LIKELY WITH THIS SIGNIFICANT AREA OF RAIN FRIDAY NIGHT INTO SATURDAY."

The chances for rain will continue into Monday as the storm makes its leisurely exit.