More freezing rain tonight; more snow Friday
Keeping up with the forecasts, the watches and advisories today is like playing Whack-a-Mole. The landscape has changed again. Here's how it looks for now:
A Winter Storm Watch remains in effect for the northern tier of counties, from Washington County in the west, to Harford in the east. That means there remains a chance for a quarter-inch of new ice accumulations today through Wednesday morning. Precipitation which may slow or end this afternoon, is forecast to resume, intensify and change to rain tonight. A quarter- to a half-inch of rain is possible by noon Wednesday. UPDATE: The watch was cancelled Tuesday afternoon.
A Freezing Rain Advisory has been posted from Washington to Harford county and as far south as Howard and Montgomery, effective from 9 p.m. Tuesday evening until 11 a.m. Wednesday. It means these locations could see several tenths of an inch of accumulating ice before the precipitation changes to rain sometime during the night. Highest icing amounts would be near the Mason-Dixon Line. Baltimore City, Anne Arundel and PG counties could see a tenth of an inch.
A Winter Storm Warning is in effect just north of the Mason-Dixon Line in Pennsylvania. Here's the bad news for the Keystone State:
"ACCUMULATIONS...3 TO 6 INCHES OF SNOW AND SLEET NORTH OF
INTERSTATE 80. 1 TO 2 INCHES OF SNOW AND SLEET SOUTH OF
INTERSTATE 80 BETWEEN ROUTE 22. LITTLE TO NO SNOW OR SLEET
ACCUMULATION FROM THE PENNSYLVANIA TURNPIKE SOUTH TO THE
MARYLAND BORDER. SIGNIFICANT ICE ACCUMULATION BETWEEN ONE
QUARTER AND ONE HALF INCH ALONG AND SOUTH OF INTERSTATE 80."
UPDATE, 1:25 p.m.: Here's Eric the Red's take on tonight: "Tonight (Tues. night) will be a very close call, with ice possible until 4 a.m. close to I-95, but lasting a bit longer in northern and western Maryland before changing to cold rain shortly after sunrise thanks to an east wind. This does not look like a crippling ice storm, but will be worse in northern and western Maryland for sure."
Here's Prof. Jeff Halverson, at UMBC. He has been watching relatively warm air gradually erode the cold air at the surface, and he sent this weather map, showing the (purple) freezing line, and the big precipitation hanging to our west:
"Consistent with the steady erosion of the cold air dam (CAD), the 32 F isotherm has notwpushed north of Montgomery Co., and now straddles Baltimore. I see this trend continuing. We could well be into 40 degree air by sundown. Note the very heavy rain well to the west - this line won't blast through until around dawn. I expect it will be all liquid, everywhere around Maryland."
And here's the big picture from AccuWeather.com
Oh yes. The forecast also includes mention of a new coastal low that's predicted to form off the Southeast coast Friday and move northeast. So far, the 7-day forecast for BWI-Marshall sets a 40 percent chance for snow Saturday and Saturday night, with highs near 40, falling to the mid-20s.
Whatever falls won't last long. The rest of the weekend looks sunny, with temperatures rising to 50 degrees by Monday.