The National Weather Service in Pittsburgh has issued a flood warning for southern and southwest Butler County until 9:45 a.m.

The warning was issued about 7 a.m. and followed heavy rain overnight.

A growing concern is the swollen Connoquenessing Creek in Zelienople, which has risen to 8.6 feet, according to Lee Hendricks, a meteorologist at the weather service. Flood stage is 10 feet.

“Looking at the trend in the rise,” Hendricks said, “I don't see it beginning to crest until we reach flood stage.”

The estimate is that the creek may not crest until it hits 11 to 11.5 feet.

Officials are keeping particular watch on the bridge on West New Castle Street over the creek, which has been identified as “susceptible for flooding,” the weather service said.

Rising waters in the past have closed the bridge to traffic, causing detours for motorists traveling to Beaver County and Ellwood City.

As of 7 a.m., according to the Butler Area Sewer Authority in Butler Township, 1.99 inches of rain have fallen since Sunday afternoon.

The rain gauge at the Butler County Airport showed a rainfall of 2.46 inches over the same time period.

The rain accumulation has caused numerous calls to volunteer firefighters, primarily in southern Butler County, for flooded basements.

A homeowner on Summer Street in Butler Township reported 8 inches of water in his basement about 11:20 p.m. About an hour later, a resident reported a similar amount of water in his home on Whitestown Road in Butler Township.

Several roads were also flood overnight, including Dinnerbell Road in front of Knoch High School in Jefferson Township just after 11 p.m.

Hendricks said the unusually heavy rain was caused by the leading edge of a cold front colliding with a band of recent warm and moist air.

The good news is that the forecast calls for the rain to stop about lunch time. But Hendricks noted that it will take up to six hours for the runoff to take its course before waters subside.

No additional precipitation is forecast until Saturday evening, when snow showers are likely.