After a week of warmer temperatures, Butler County is expected to see another snowfall Wednesday into Thursday.

With the forecast calling for heavy accumulation of snow, Butler County is under a winter storm warning until at least 7 a.m. Thursday.

While the National Weather Service’s Pittsburgh office originally issued a winter storm watch for the county Tuesday, it upgraded that to a warning based on indications there would be likely around 6 inches of snow.

Allegheny, Armstrong, Fayette, Greene, Washington and Westmoreland counties also fall under the snow warning, which projects accumulation of 5-8 inches across the region.

Myranda Fullerton, a meteorologist with the NWS in Pittsburgh, said the criteria used to upgrade a watch to a warning include the accumulation of 6 or more inches in a 12-hour period, or 8 or more inches in 24 hours.

The snow — which Fullerton said will likely be heavy and wet — is expected to begin accumulating by mid-morning or early afternoon Wednesday, with the heaviest periods occurring around the evening rush hour.

“The evening commute home for those who are commuting could be very treacherous,” Fullerton said. “The main message here is to expect a period of heavy, accumulating snowfall.”

Heavier snowfall is expected in the eastern segment of the county, Fullerton said.

PennDOT District 10 also issued an alert, telling drivers to be cautious while driving in wintry weather. Among its list of tips, PennDOT says if drivers encounter snow squalls, they should drive at speeds that suit the conditions, turn on their headlights and keep windows and mirrors clear of snow and ice.

PennDOT also reminds motorists that roadways will not be clear of ice and snow when the snow is falling, and urges drivers to pack an emergency kit for their vehicles.

This is a breaking news report.