It doesn't feel like fall anymore, what with snow in the air overnight, plunging temperatures, all the mittens and scarves and - oh, yes - the arctic sea smoke.
No, it's not coming from Santa's pipe, but it is being delivered from somewhere near the North Pole, forecasters said.
With a sharp outbreak of polar air bearing down on the Chesapeake Bay yesterday, the National Weather Service issued warnings for "arctic sea smoke" on the tidal Potomac and Maryland portions of the bay.
"This is the first time I've seen it forecasted here," said Calvin Meadows, a meteorological technician who has worked since 1986 at the weather service's forecast office in Sterling, Va.
Temperatures were taking a 10- to 20-degree dive across the region late yesterday as the arctic outbreak swept into Maryland from the north and west. Heavy snow showers accompanied it just before 6 p.m. in southern Maryland, quickly coating roads and slowing traffic on Md. 301 to a crawl near Waldorf.
The snowfall and icy conditions apparently caused several accidents on the Bay Bridge, and both spans were closed for about two hours last night while salt trucks did their work.
Snowflakes filled the air in downtown Baltimore shortly after 6:30 p.m. With the snow came reports of slick roads and fender-benders. About 10:30 p.m., city police reported a six-car crash on Northern Parkway at Charles Street, but no injuries.
Lora Rakowski, a spokeswoman for the State Highway Administration, said 350 pieces of equipment had been deployed to salt roads in preparation for the morning commute in the counties around Baltimore and Washington.
No more than an inch or two of accumulation was expected in the region. But frigid temperatures and stiff winds were expected to make things wintry today.
"Definitely, the first winter cold outbreak is upon us," Meadows said.
And with it, arctic sea smoke. The fog-like phenomenon occurs when very cold air blows across much warmer water. Evaporating moisture condenses in the frigid air and forms a low cloud that can cut visibility for mariners.
The newly arrived arctic air mass was expected to send temperatures into the teens overnight and hold today's highs to no more than about 24 degrees, forecasters said.
Meanwhile, water temperatures in the Chesapeake remain just under 50 degrees.
There's no set temperature spread between air and water that determines when arctic sea smoke forms, Meadows said. "It's more the type of air mass that's moving over the water." This one, he said, "is a very cold arctic air mass that originated over northern Canada, above the Arctic Circle."
Temperatures in Hagerstown began plunging about 2 p.m. yesterday, falling from 42 degrees to 25 degrees at 6 p.m. At Martinsburg, W.Va., the mercury dropped from 43 to 27 in three hours. By midnight, the temperatures had dropped to 15 in both cities - and the Baltimore area was nearly as nippy at 19 degrees.
The approaching cold air was not expected to generate more than an inch or two of snow east of the Allegheny Mountains.
But lake-effect snows, caused by the cold air blowing across waters of the Great Lakes, were delivering significant accumulations late yesterday to portions of northwestern and western Pennsylvania and upstate New York.
Heavy snow and treacherous driving conditions yesterday morning contributed to a pileup of nearly 80 cars on Interstate 80, near the Ohio state line in Pennsylvania. Numerous injuries were reported.
Those heavier snowfalls were reaching Maryland's far-western Garrett County, where the forecast called for 5 to 8 inches before it was over today and as much as a foot of snow on the ridge tops. Wind chills there were likely to plunge to between minus-10 and minus-20 degrees Fahrenheit.
Whatever snow hits the ground in Central Maryland is not expected to hang around until Christmas.
"Temperatures are going to rebound rather rapidly over the next few days from this arctic outbreak," Meadows said. Rain could fall around midweek.
But there was at least a glimmer of hope there will be some snow for Christmas.
Although daytime highs will reach the 40s across the region, Meadows said, there might be snow showers Friday or Saturday. "There's a 30 percent chance of snow showers Christmas morning," he said.
Sun staff writers Lynn Anderson and Richard Irwin, and the Associated Press contributed to this article.