By Scott Dance, The Baltimore Sun
10:49 AM EST, February 20, 2013
Forecasters are watching another possible mess of a light wintry mix on Friday. As the window for a big snowfall narrows, though, at least one forecaster still sees favorable snow chances in the weeks ahead.
Meteorologists are watching two key climate patterns that influence storm tracks, and Friday, they are expected to butt heads, helping to keep the forecast for Maryland tricky.
One indicator known as the North Atlantic Oscillation, known for sending monster snowstorms up the East Coast, is helping push some precipitation through the area. Another pattern, the Pacific/North American, is meanwhile leaning toward sending warm air our way up from the south.
That could mean some snow at the start of any precipitation on Friday, with the cold air that has settled in over the area Wednesday to remain into Friday. But that warm air from the south could turn that snow into a wintry mix.
"Cold air will be pushed down the coast via our northern Atlantic high, while the high over the southeast attempts to push warm air at us from the south," writes local meteorologist "Eric the Red." "This warm air will encounter the cold air stuck near the ground and literally ride up over top of it."
Sleet and freezing rain form when there is a layer of warm air above a layer of cold close to the ground, making any frozen precipitation melt as it nears the ground before quickly re-freezing.
The National Weather Service's Baltimore/Washington office is expecting moisture to be relatively light, with less than a quarter of an inch of liquid precipitation starting as a wintry mix by midday before turning to rain into the evening. Temperatures are forecast to be cold, but not quite cold enough at the mid-to upper 30s with wind chills below freezing.
February is typically the snowiest month of the year at BWI Marshall Airport, with about 8 inches, on average. So far it has been the least snowy month of the winter, with half an inch plus some traces recorded on a few days.
So far this winter, 4.8 inches have fallen at the airport, compared with the average of 18 inches in a season.
AccuWeather.com's Henry Margusity said via Twitter on Wednesday morning that he expects the opposing climate patterns making Friday's forecast difficult could soon get in sync, though, promoting chances for more East Coast storms.
"Neg NAO and Pos PNA means to me that a big storm will eventually hit the East coast within the next two weeks," he wrote.
Are you holding out for more snow chances or ready to move on to spring?
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