A sudden, heavy snowfall caused a rash of accidents across the district today, including a crash on Interstate 79 in Robinson that killed a 13-month-old boy.

State police reported that Judah Scrutchins was in a northbound SUV on I-79 that crossed the grass median and struck a southbound tractor trailer head on near the Crafton exit around 9:22 a.m. The boy died at the scene. His female twin, Julia, and 4-year-old brother, Jaxon, were taken to Children's Hospital. All were in child safety seats.

The driver, Tracy Gebhardt, 34, of New Brighton, mother of the children, was taken to UPMC Presbyterian. Her front seat passenger, Laura Kay Federoff, 34, of Lake City, Erie County, was taken to Allegheny General Hospital. The conditions of Ms. Gebhardt and the surviving children were not available, but Ms. Federoff was in critical condition.

The tractor trailer driver was not injured.

The snow started around 9 a.m., and soon after, emergency dispatchers began receiving numerous calls about crashes.

Outbound traffic on the Parkway West was stopped for nearly two hours due to multiple crashes in the Carnegie area.

Crashes were also reported on Banksville Road, the Boulevard of the Allies, the West End Bridge, the Fort Duquesne Bridge, Route 28 and in several spots on Ohio River Boulevard. State police alone reported responding to 18 incidents in the county.

Crashes were still being reported into the afternoon.

Pittsburgh Councilman William Peduto said he encountered three wrecks on his drive down Fifth Avenue toward Downtown.

"I was in one," he said. A car pulled out in front of him at Fifth and Denniston, he said, and due to ice he slid into it. No one was hurt, and his Cooper Mini was undamaged. "My car bounced off his car."

He said he saw "no snow plows. . . . It's snow, snow, snow, then ice. Ten miles an hour."

City Public Works Director Guy Costa said his crews "have been treating the roads since 9:00, when it started to snow."

He said the city had 50 salt trucks loaded and ready to go, and deployed them as soon as the snow started. "The bad thing is, it came down fast," he said. Wind blew snow back on the roads after they were cleared.

"We're going to have light snow between now and 5:00," he said. "We should be O.K., based on the forecast."

He said the snow ended around 10:30, and he anticipated that all primary roads would be cleared and salted within four hours of that time. Secondary roads are to be cleared within eight hours of the end of snow fall, he said, and tertiary roads will be cleared overnight.

"We've got 1,200 miles of streets, and it takes time," he said.

At 12:15 p.m., Port Authority spokesman Dave Whipkey reported that some bus routes were experiencing delays of up to an hour. He said problems were reported in many areas of the county.

Mr. Whipkey said buses were involved in a couple minor accidents between 10 and 10:45 a.m., but no injuries had been reported.

But with the snow apparently ending, Mr. Whipkey said the buses should be back on schedule for tonight's rush hour.

The National Weather Service in Pittsburgh said as much as two inches may fall in the city and suburban areas with the potential for more accumulation in the higher elevations. Most of the snow was expected to fall by 2 p.m. Expect moderate winds of less than 20 mph to blow around the snow.

Travelers should be aware that a winter weather advisory is in effect for the mountain areas in central Maryland and the eastern panhandle of West Virginia.

Check out the latest conditions and forecast. Commuters also can access the updated traffic conditions.