A winter weather advisory is in effect through Tuesday night's commute, and a winter storm watch is meanwhile posted warning of the potential for 5 inches of snow Thursday.
Up to half an inch of snow and sleet and a tenth of an inch of ice is possible through Tuesday night, with higher totals possible near the Mason-Dixon Line, according to the National Weather Service. That prompted schools to close early around the region (Find complete school closings updates at bsun.md/snowday).
Heavier snow, meanwhile, is forecast Thursday.
A winter storm watch is in effect for Wednesday night through Thursday night. Rain on Wednesday is forecast to turn to wet, heavy snow overnight, with 4-6 inches of accumulation forecast across Central Maryland.
For Tuesday evening's commute, meteorologists expect surface temperatures to be cold enough for slippery conditions. It was 30 degrees at Baltimore-Washington International Thurgood Marshall Airport as of 3 p.m.
"This storm has the potential to significantly impact today’s rush hour with a snow and ice combination," said SHA Administrator Melinda B. Peters. The administration urged drivers to stay off the roads during the storm, if possible.
Rain is forecast to wash away much of the ice and some snow by Wednesday morning. Warmer air is expected to move in overnight, reaching the upper 30s by daybreak and possibly the upper 40s by Wednesday afternoon.
But the break from cold is expected to be short. More frigid air is expected to come in behind a cold front Wednesday night into Thursday, turning showers back to a wintry mix and snow late Wednesday night through Thursday afternoon.
A cold front is expected to move in overnight Wednesday into Thursday, bringing more frigid temperatures and 5 inches of snow or more. Depending on how quickly cold air rushes in and how intensely precipitation develops, the region could see at least a few inches of snow and potentially 8-10 inches or more.
"It does look like we’re going to need the snow shovels on Thursday," said Tom Kines, a senior meteorologist with AccuWeather.com. "It’s a matter of if its 3 inches or 10 inches. I think that’s the question mark."
Highs are forecast in the 40s Wednesday – actually right about normal for this time of year, if not still slightly colder than average. But temperatures are expected to drop to the mid-20s by early Thursday morning, turning Wednesday’s rain showers into snow some time between nightfall and daybreak.
The National Weather Service is predicting 4-6 inches of snow across Central Maryland, with the potential for as little as an inch or two and as much as a foot close to the Mason-Dixon Line. Kines said how much falls depends on how quickly temperatures drop overnight and where the heaviest bands of precipitation set up.
The region saw an 8-inch snowfall over two days last March, but before that, there hasn’t been so much snow during the first month of meteorological spring since a foot fell in March 1993.
Below-freezing temperatures with clear skies and sunshine are forecast Friday.