Multiple Pittsburgh-area counties under flood watch as ice jams and rain cause concern

A flood watch is in place for several western Pennsylvania counties until Friday afternoon as rain and higher temperatures could lead to ice jam flooding. 

The watch covers Armstrong, Butler, Clarion, Fayette, Forest, Indiana, Jefferson, Lawrence, Venango and Westmoreland counties until 1 p.m. Friday. 

Ice jams could raise water levels quickly

The snow depth for Pittsburgh officially hit zero at 7 a.m., the National Weather Service said, making it the first time since Jan. 14 that there hasn’t been a measurable snow pack or a trace.

But the warmer temperatures come with the threat of flooding. The NWS said the Youghiogheny and the Allegheny rivers may see some ice movement over the coming days. Ice jam flooding comes with little warning, the NWS said, and people near rivers and creeks are reminded to stay vigilant. 

The North Sewickley Township Police Department alerted residents just before noon on Thursday about rising water levels, adivisng people who live along the Connoquenessing Creek to evacuate. Nearby, the New Sewickley Fire District warned people in Marion Township of rising water levels due to ice jams. 

When will the rain arrive? 

Scattered showers are forming in advance of a warm front, which will move towards the Pittsburgh metro around Thursday evening. A more widespread and potent wave of rain and thunderstorms arrives overnight into Friday morning.

While states west could see severe storms, the intensity is expected to diminish as they head toward Pennsylvania. Despite that, some non-severe thunderstorms and pockets of heavy rain are still likely between 11 p.m. to 6 a.m. Friday. 

Most areas will receive around half an inch, but with training storms, some isolated 1 to 1.5 inches are possible, which could lead to localized flooding. 

As the cold front with this strong area of low pressure moves east during the midday to early afternoon hours of Friday, isolated thunderstorms can’t be ruled out between 10 a.m. to 1 p.m. There is a very low-end potential that anything could turn strong to severe. 

Falling temperatures and gusty winds will occur behind the boundary with gusts upwards of 40 to 50 mph through the evening. Some wrap-around rain mixed with snow showers is possible tomorrow evening for areas near and north of I-80.