NWS: "Winter has not quite retired yet"
There are more snowflake icons on the seven-day forecast from the National Weather Service this week. A stubborn high-pressure system parked over Central Canada is pumping lots of cold air into the Eastern United States. Add a series of weak storm systems gliding along the jet stream just south of the cold air and we get a risk of mixed rain and snow this week.
Central Maryland will have to shake off some clouds today as another storm system passes through Virginia, with some snow for the Carolina mountains. But northwest winds should eventually clear our skies, and we can look forward to more sunshine on Tuesday.
Daytime temperatures, however, will remain stuck in the 40s Monday. That's 10 to 15 degrees below the average for this time of year at BWI-Marshall Airport. Overnight lows will dip to the upper 20s Monday night, with colder readings away from the city centers and the bay. That's also 10 to 15 degrees below the norm.
More sunshine on Tuesday is forecast to bring our temperatures into the low 50s. But the first storm system will send precipitation northeastward into our area late Tuesday into Wednesday. With cold air wedged against the eastern slope of the Appalachians, that raises the possibility of some frozen stuff.
Forecasters at the NWS regional forecast office in Sterling, Va. say we're in a better position this time to see some precipitation, and possible some snow, than we were on Sunday:
"Primary uncertainty lies in [the] influence of cold air near surface. Surface low pressure developing in coastal Carolinas ought to help maintain cool wedge at surface during this event."
"At the moment, the possibility has increased for a significant snow accumulation for portions of the forecast area. Warm air near the surface likely to be quite shallow, so it seems likely that precipitation will change to snow in most locales eventually during the event. All models show snow during this period. But the uncertainty lies in amount and duration."
"SREF members [an ensemble of several forecast models] nearly unanimous in depicting snow in excess of 1 inch on Wednesday for most counties west of Blue Ridge. Half of the SREF members also show possibility of snow in excess of 4 inches on Wednesday. It does appear that winter has not quite retired yet."
After a break on Thursday, we're looking at a chance for more rain and snow Thursday night into Friday, and rain on Friday night.
AccuWeather.com's Henry Margusity is talking up a "big" Friday storm, with heavy, wet snow to our west and north, and "rain changing to snow" for the "big cities." No hint of that yet for us in the NWS forecast.
Prof. Jeff Halverson, at UMBC's Jt. Center for Earth Systems Technology, sees nothing of the kind:
"This time of year, climatology argues strongly against snowfall in the Mid Atlantic east of the mountains; heavy snowstorms are possible in early spring across south-central Appalachians, but are quite rare. Not impossible here, but the odds really do stack up against anything more than a cold, rainy day."
The weekend looks better, with some sunshine and more seasonable highs in the 50s. But it may be weeks before we see the really warm weather we're longing for. AccuWeather.com's Paul Pastelok says this chillier pattern could hold on until May.