The National Weather Service is forecasting up to 8-10 inches of snow on top of a layer of ice across Central Maryland by Monday night, with sleet and freezing rain expected Sunday night, turning to heavy snow into Monday.
Forecasters remain uncertain how quickly precipitation might switch from sleet and freezing rain to snow, which could affect where the heaviest snowfall accumulations occur. That could also affect how much ice might accumulate before any snow falls. Precipitation was expected to start as rain Sunday evening.
As of late Saturday, the National Weather Service predicted the heaviest snow accumulations of 8-10 inches across Central Maryland, including Baltimore and Washington, D.C., with accumulations of 4-6 inches closer to the Mason-Dixon Line.
"Confidence has increased that this will be an event that will have significant impact," said Carl Barnes, a meteorologist with the National Weather Service in Sterling, Va.
A winter storm watch was in effect for all of central, western and southern Maryland and the upper Eastern Shore from late Sunday night through Monday evening. Winter storm warnings and winter weather advisories meanwhile stretched from Montana through the Heartland and Midwest and to the mid-Atlantic.
Weather service forecasters expect a glaze of ice up to 0.05 inches thick before the snow, with about an 80 percent chance of 4 or more inches of snow, and a nearly 60 percent chance of 8 inches or more. Those chances were raised from predictions made earlier Saturday, as forecasting models suggest the air in place over the region will be colder than previously expected.
The snow as forecast would make this the snowiest March here in at least five years, and it is already the snowiest winter since the winter of "Snowmageddon", 2009-2010.
So far this winter, 26.9 inches of snow has been measured at Baltimore-Washington International Thurgood Marshall Airport. The norm for a season is about 20 inches; while a record-setting 77 inches fell in 2009-2010, a total of 24.2 inches fell over the next three winters combined.
On average, 1.9 inches of snow falls every March here. Last March, 3.2 inches of snow fell, and there was 5.8 inches of snow in March 2009 and 7.6 inches of snow in March 1999.