A biting cold front from Canada turned the Washington area's melting snow to ice yesterday, snarling rush hour traffic, delaying the opening of some schools and causing a bus carrying Fairfax County high school students to skid into a snow embankment.

No one was injured in the 1 p.m. bus accident, Fairfax County police said. The bus, carrying about 35 Langley High School students returning from vocational classes at other schools, skidded on a patch of ice and landed upright in a ditch after swerving to avoid an oncoming car.

Temperatures dipped into the teens in the suburbs Sunday night, with Dulles International Airport reporting a low of 12 degrees. Yesterday's high of 33 was recorded at 2 p.m., and a strong sun over clear skies helped melt some of the snow that fell over the weekend in depths up to 11 inches.

National Weather Service forecasters said today would be sunny and warmer, with temperatures in the low to mid 40s. As the snow melts and the ground warms, forecasters said, temperatures should reach the upper 40s to mid-50s later this week. By Thursday or Friday, a storm developing over the Gulf of Mexico, similar to the one that brought last weekend's snow, may bring more snow or rain, forecasters said.

Public schools in Fairfax, Prince William and Anne Arundel counties opened two hours late yesterday, and openings were delayed one hour in Montgomery, Loudoun, and Prince George's counties.

At Laurel Race Course, bettors were sent away after the first race when jockeys refused to ride because of slippery track conditions. A track official said no difficulties are anticipated today.

Traffic delays were reported throughout the area as motorists skidded, slipped and banged fenders on icy roadways, but no major accidents were reported.

"The side streets in shaded areas are icy," said Alexandria police officer Michael Saller. "It's that black ice that you don't see until you hit it."

D.C. police said there were delays of up to 30 minutes on some major commuter routes and that streets shielded from the sun by high buildings were particularly icy. By Sunday evening, following the ministrations of 88 salt and sand spreaders and plows, most of the District's major streets and residential roads were clear. But many curb lanes remained clogged because cars had remained parked there over the weekend.

The city's snow-removal effort cost $30,000. Bernard O'Donnell, deputy director of the D.C. Department of Transportation, said that the city, faced with a potential budget deficit, was cautious in expending money on the first major snowfall of the year. "Everybody said, 'you could have done more,' but the economics come into it."

Mike Burton, of the Northern Virginia office of the Virginia Department of Highways, said his department spent $160,000 on the weekend storm, about 8 percent of the year's snow removal budget. "This was a fairly easy storm to contend with," Burton said. Yesterday, highway department crews concentrated mostly on plowing and sanding Fairfax County's numerous subdivisions.

"It looks like we're through with most of the mess," said National Weather Service forecaster Frank Rosenstein. "At least until Thursday."