If there's one message to heed today, it's this: Stay off the roads.
The year's first major snowstorm is expected to blow through the area with a fury - dumping up to 10 inches today in some parts with wind gusts of up to 40 mph.
The storm is expected to be widespread, touching cities from Richmond, Va., to Boston, with New York bracing for blizzard conditions and more than a foot of snow.
"This storm is going to affect millions of people," said Brian Guyer, a meteorologist with the National Weather Service in Sterling, Va. "We're talking everywhere between Richmond, Pittsburgh, New York, Binghamton [N.Y.], Boston and Hartford [Conn.]"
The Baltimore area, like much of the state, is under a winter-weather warning. The threat of severe weather forced school systems to cancel activities today, including administering the SAT.
Snow is expected to start between 7 a.m. and 10 a.m. and last until about 7 p.m., said Guyer. Temperatures will hover around 20 degrees with a windchill of zero, he said.
Transportation crews began preparing yesterday, mobilizing snowplows, dump trucks and salt trucks and putting workers on 12-hour shifts.
"Our plow trucks will be up and ready at 5 a.m., ready for the first snowflake," said James F. Ports Jr., deputy secretary of the Maryland Department of Transportation.
The heaviest snow should fall between noon and 6 p.m. at a rate of 2 inches to 3 inches per hour at times, said Guyer. Accumulations are expected between 5 inches and 10 inches in the metro area, and up to a foot near the Pennsylvania border. Anne Arundel County can expect between 4 inches and 8 inches, with the southern part of the county receiving a mix of snow and sleet, he said.
More snow could fall overnight, but how much depends on the storm's path, Guyer said.
"There's a possibility that the storm could regenerate ... and act like a typical nor'easter wrapping more snow into the area," he said.
In the city, transportation crews were preparing to use this year's big purchase: blue salt, about 1,000 tons of which has been tested in four neighborhoods. The colored salt is supposed to help residents identify which streets have been plowed.
Buses and trains are expected to run, and Baltimore-Washington International Airport is expected to be open, Ports said last night. But he urged people to check before going to the airport or train and bus stations.
Cancellations announced yesterday included all weekend school activities, including the SATs, in Anne Arundel, Howard and Harford counties.
Charles Herndon, a spokesman for Baltimore County schools, said last night that the system was planning to go ahead with the test. He said students planning to take the test should call 410-887-5555 for updated information.
Baltimore schools spokeswoman Edie House said the system would decide this morning whether to cancel the SAT. Students can call 410-396-8700, or visit the system Web site.
Transportation officials warned of poor road conditions.
"Make sure that you drive the appropriate speed for the weather conditions," said Ports. "Keep in mind that bridges and ramps freeze first and fastest. What may appear to be wet pavement could be ice. Please make sure you clear all of the snow from your vehicle. Windows, headlights, tail lights."
"If you don't have to be out, stay home," he said. "Put your slippers on. Enjoy the family."
Sun staff writers Julie Bykowicz, Liz F. Kay, Laura Loh, Sara Neufeld and Howard Libit contributed to this article.