A winter weather advisory is in effect for Pittsburgh and most of southwestern Pennsylvania until 7 p.m. Saturday.
The National Weather Service in Pittsburgh issued the advisory Thursday for Allegheny County and counties ranging from Armstrong, Lawrence, Butler and Beaver in the north and west to Greene and Washington in the southwest. Northern West Virginia and much of eastern Ohio is included in the advisory area, as are parts of Westmoreland and Fayette counties.
The advisory calls for as much as 3 to 5 inches of snow and winds from the west at 15 to 25 mph with gusts to 40 mph in the Pittsburgh region and more snowfall in the mountains.
Pittsburgh declared a Phase 1 alert and said it expected 2 to 4 inches within city limits. Road crews were prepared to work 12-hour shifts if needed.
The storm is part of a system that began in the Rockies earlier in the week before trekking into the Midwest, dropping a foot of snow in parts of Wisconsin and Iowa, where it contributed to a fatal 25-vehicle pileup.
On the southern edge of the system, tornadoes destroyed several homes in Arkansas and peeled the roofs from buildings, toppled trucks and blew down oak trees and limbs in Alabama.
Widespread rain began falling in the Pittsburgh area around 1 p.m. Thursday, and residents of the city and suburbs were expected to see as much as three-quarters of an inch of rain before changing to snow overnight.
National Weather Service meteorologist Lee Hendricks said snow showers could cause some slick spots for the morning commute, especially on bridges and overpasses.
Drivers also should watch for water that accumulates on roadways. With falling temperatures, it could cause some icy patches.
A winter storm warning is in effect from 11 a.m. today to 7 p.m. Saturday for the Interstate 80 corridor north of Pittsburgh, including the counties of Mercer, Venango, Forest and Clarion.
The Laurel Highlands area also is under a winter storm warning, with the higher elevations of Westmoreland, Somerset and Fayette counties expected to get 8 to 14 inches of snow blown by winds gusting to 45 mph.
The warning also extends to the ridges of West Virginia and western Maryland, including the I-68 corridor. Preston and Tucker counties in West Virginia and Garrett County, Md., were among the areas hit hard by Superstorm Sandy in late October.
The website FlightAware reported more than 1,000 cancellations of U.S. flights as of early afternoon Thursday, with most of those concentrated in Chicago, Minneapolis and Kansas City.
Southwest Airlines canceled two scheduled Pittsburgh departures to Chicago Thursday afternoon.weather - mobilehome - region
Jon Schmitz: firstname.lastname@example.org, 412-263-1868 or on Twitter, @pgtraffic. Molly Born: email@example.com, 412-263-1944 or on Twitter, @borntolede. The Associated Press contributed. First Published December 21, 2012 5:00 AM