There were some white-knuckle moments for morning commuters today.

The predicted storm system came true with snow arriving about 3 a.m. And there's been no let up.

The white stuff began accumulating rapidly in Butler County, according to the National Weather Service in Pittsburgh with snowfall rates of 1 inch to 1½ inches per hour.

Butler County schools are closed and state police and county 911 dispatchers have reported a number of disabled vehicles, mostly stuck on hills, and the occasional slide-off accident.

At 7 a.m., five vehicles were reported stuck on Armco Hill in Butler Township. About the same time, the 911 center got a call for a tractor-trailer struck on Route 228 eastbound just past Northwest Bank in Cranberry Township.

Jackson Township police also advised just before 7:30 a.m. that there were “multiple disabled vehicles” on Lindsay Road at Route 19.

No major crashes, however, have been reported.

PennDOT and local road crews have all available plows out on the roads, but the unrelenting snowfall for time was making it tough for them to keep up.

“So far, we're maintaining things,” said Chris Schneider, PennDOT District 10 acting assistant maintenance manager in Butler. “We're plowing everything off and treating.”

“We're trying to keep it slushy so we don't get a snow pack.”

PennDOT began treating roads with salt brine about midnight and its full fleet of 42 trucks has been working non stop.

Butler County remains under a winter storm warning until 6 p.m. The forecast is for the proverbial wintry mix of snow, freezing rain and sleet.

In southern Butler County, the snow began to change to freezing rain by 7 a.m. But by noon, the precipitation is to return in the form of snow.

“But the northern half could get all snow,' said weather service meteorologist Alicia Miller. “It's a real sharp cut off.”

The daytime snow accumulation could be anywhere from 4 to 7 inches, Miller said. From Butler south, there could be up to a quarter inch of ice, too.

The worst of it should be over by 2 to 3 p.m.

On Thursday, there's a slight chance of snow showers before 11 a.m. It's supposed to be a mostly cloudy day with a high near 23.