Pittsburgh Mayor Luke Ravenstahl this afternoon asked residents to stay home, if possible, for the rest of today so that city road crews can clear the snow and spread salt to combat the sleet.

Crews have been out all day, but Mr. Ravenstahl acknowledged that many city streets are slippery and snow-covered. The snow began falling early this morning, and city trucks have primarily been using plows to try to keep the roads clear.

As the snow changes to sleet and then freezes later today, the crews will be salting.

The mayor sent other city workers home early today. He did not ask private Downtown offices to send their workers home early. During some past snowstorms, a sudden exodus of Downtown workers in the afternoon caused congestion that prevented road crews from treating streets.

Allegheny County courts did close early, as did several colleges.

And many Downtown workers obviously decided to leave early. Bus stops were jammed by 3 p.m., well ahead of rush hour.

The Port Authority predicted the evening rush hour would be a bit slower than usual but relatively few bus routes have been affected by accidents or the weather, spokesman Bob Grove said.

"We're running maybe 5 to 10 minutes behind because traffic is moving slower than usual," he said late this afternoon. "But this isn't like a major snow event where we'd be 30, 40 or 50 minutes behind schedule. We're coming through today pretty well, all things considered."

There have been exceptions, but they were attributed to traffic accidents, including a U.S. Postal Service truck that overturned on Route 28 between the North Side and 40th Street Bridge, closing the four-lane artery and delaying buses that use the corridor by up to an hour earlier today.

Around 3:45 p.m., a tractor-trailer jackknifed at 18th and Josephine streets on the South Side. Mr. Grove said it was too early how that might impact buses that pass through that area

Because PennDOT forces were busy battling the elements on main traffic routes today, the HOV lanes on the Parkway North had a delayed opening until crews could clear the lanes. They were expected to be open by 4 p.m.

The National Weather Service in Pittsburgh is continuing to forecast 3 to 5 inches of snow today, with another 1 to 3 possible tonight and 1 to 3 more tomorrow.

Highway agencies said they expected their biggest challenges to occur this afternoon when the sleet and freezing rain began falling on top of the snow. The sleet began around 2:30 p.m.

Mr. Grove said this morning's rush hour did not pose major problems.

"Any delays we had were due mostly to traffic situations," or minor accidents, he said. "Only three bus routes lost a few stops, in hilly areas like Bon Air" in the southern part of the city. "The busways have been pre-treated with brine and we're out there salting right now."

Mr. Grove said continuing snow will keep workers from clearing major bus and light-rail stations and stops, so riders need to be careful. "There are just too many facilities to clear all of them at all times," he said. "Everybody is doing the best possible job."

Areas south of Pittsburgh and in the Laurel Highlands were hard hit from the start, with up to several inches already on the ground by 10 a.m. Many schools canceled classes and indicated they're likely to do so again tomorrow if the snow continues, as predicted.

The morning wasn't without its problems. A crash closed Washington Boulevard in both directions between Allegheny River Boulevard and Negley Run Boulevard just before 10 a.m. And state police said UPMC Bedford Hospital reported it was "experiencing an overload of incoming patients" due to crashes associated with the weather. Police said they assisted with numerous disabled vehicles along the hughways.

"The best advice is to stay home if you can," Uniontown-based PennDOT District 12 spokeswoman Valerie Petersen said. "Later, people need to be on the alert for drifting, especially where wind sweeps across flat areas and pushes the snow onto roads."

PennDOT expected to have fresh forces on duty for this afternoon's rush hours. The "B" crews report at noon and will stay on duty through midnight, when the "A" crews begin their 12-hour shifts.

"We're in the 24-hour mode," said District 11 spokesman Jim Struzzi said.

For hour-by-hour forecasts, check the Weather Page at post-gazette.com.

More details in tomorrow's Pittsburgh Post-Gazette.