The third wet winter weather system to pass through Maryland in a week was expected to add to the young season's snow tally Saturday, but a late start and some drier air could make it difficult except in areas north and west of Baltimore. Snow was beginning to taper off southwest of Baltimore by early afternoon.
The National Weather Service is expecting an inch or less in the Baltimore area, with 1-2 inches further north and 2-4 inches possible along the Mason-Dixon Line. Rain and sleet are expected to mix in for areas along the Interstate 95 corridor and points south. Snow and sleet started falling in parts of Central Maryland about 10 a.m., including downtown, along the Interstate 70 corridor and in northern Baltimore County, according to State Highway Administration data.
A winter weather advisory for Carroll, Howard, northern Baltimore and Harford counties was canceled about 3 p.m. Forecasters canceled an advisory for Howard County about 2 p.m.
But warm air threatening to move in could limit accumulations, particularly in Baltimore and points south, said Brian Lasorsa, a meteorologist with the weather service's Baltimore/Washington forecast office in Sterling, Va.
"It will be a light snow event for most of the area," Lasorsa said.
A "dry slot" of air wedged between low pressure systems off the coast and moving through the Ohio Valley prevented the snow from starting in the early morning as was expected, according to Foot's Forecast and other local weather blogs.
Early snow totals had 0.8 inches in Long Green, Brooklyn Park, Dundalk and Eldersburg as of before noon, according to weather service reports. Higher totals were reported in Carroll County Saturday afternoon, with 2.8 inches near Westminster, 2 inches in Hampstead and 2 inches in Mount Airy.
State highway crews were preparing for treacherous travel conditions, particularly in the morning, and urged motorists to stay off the roads.
At first light, highway crews were idle after an initial burst of snow ended abruptly. Along Route 100 in Anne Arundel County, seven plow and sanding trucks were qeued up like elephants at the circus on the ramp just east of U.S. 1.
The massive screens at State Highway Administration emergency operations center near BWI Marshall Airport showed wet roads near Salisbury and white roads in Garrett County with long stretches of black asphalt in between.
“Our response is always going to be to err on the side of an overabundance of caution,” said SHA spokesman David Buck. “We want to put the appropriate number of trucks out for the forecast. “We can never be the agency that says, ‘Whoops, we missed that one.’”
State highway traffic cameras showed snowy grass and slushy pavement in northern areas, including Westminster, Pylesville and Parkton. Further south along the beltway, snow patches were mostly confined to grassy medians.
"Even a couple of inches of snow can wreak havoc on driving conditions, so if you're planning to drive on Saturday, reconsider whether travel is necessary and stay off the roads until later in the day, if possible, to allow crews time to clear the roads," State Highway Administrator Melinda B. Peters said in a statement.
Dozens of flights were listed as delayed at Baltimore-Washington International Thurgood Marshall Airport, though airport officials said via Twitter they were minor. Delays are 15 minutes or less, according to the Federal Aviation Administration.
Like earlier systems that arrived Monday and Wednesday, possible variations in where the rain/snow line is expected to land prompted a range of forecasts from meteorologists. A trace of snow was measured at Baltimore-Washington International Thurgood Marshall Airport on Monday, while an inch was measured Wednesday.
"Our corridor, the Mid-Atlantic, is typically where the rain/snow line sets up, and this storm is no different," Nicole Listemaa, another weather service meteorologist, said Thursday.
AccuWeather.com is predicting a trace to 3 inches on the northwest side of I-95, while Foot's Forecast is calling for an inch or less around I-95, with no accumulation further south and 1-3 inches in northern parts.
The weather service's Hydrometeorological Prediction Center was calling for a 10 percent to 40 percent chance of at least 4 inches of snow across Carroll, Baltimore and Harford counties.
Garrett County could get 3-6 inches, according to the National Weather Service.
Even a little bit of snow could make this winter snowier than last year; 0.8 inches more is needed to match the paltry snowfall total at the airport for winter 2011-2012.
Sun staff writers Tim Swift and Candy Thomson contributed to this article.Copyright © 2015, The Baltimore Sun