Tropical remnants, cold front could dump up to 5 inches of rain
This week’s blistering heat is about to subside, but residents will be swapping humid heat for wet weather.
National Weather Service officials are not certain precisely where it will happen, but some places in Western Pennsylvania could be in store for a lot of rain in the next few days.
“The amounts of rain will be in the 3-to-5-inch range,” NWS meteorologist Matthew Kramar said of the coming collision between the remnants of tropical storm system Gordon and a cold front that is expected to stall over the region as the weekend begins.
“What’s uncertain is exactly where the placement of that rain will be,” Kramar said. “Based on what we see right now, our expectation is that the worst of it will be in Ohio and west of Western Pennsylvania, but Ohio’s not that far away, and a 50-mile shift can make a big change in the weather pattern.”
Fallout from Gordon is expected to bring large amounts of rain as it make its way northeast.
“Tropical systems, like decaying hurricanes, are much more efficient at building up high amounts of rain,” Kramar said.
In a typical storm, rain is produced in large drops by melting snow and ice that originates higher in the atmosphere, Kramar said. In a tropical storm, rain is generated nearer to the ground, the system is much warmer, and more, smaller raindrops are produced.
“Imagine if you take one of those large raindrops and pulverize it into a bunch of smaller drops,” Kramar said. “Those add up to a lot more in the rain gauge.”
The Pittsburgh region has received about 24.8 inches of rainfall since March 1, according to NWS climate data, with multiple flooding events in May , June and July . That came on the heels of 19.6 inches of snowfall since March 1, as winter faded into spring.
While the incoming cold front will finally bring some relief from this week’s heatwave, it also will butt up against the remnants of Gordon and create more wet weather.
“The combination of very tropical, warm, moist air and a frontal boundary like this is usually a recipe for heavy rain,” Kramar said. “You’re going to have very strong wind pulling very warm air upward. It’s going to ride over the top of the cooler air and produce a lot of rain.”
The forecast over the next few days is for widespread rain throughout the region.
“It’s going to rain everywhere,” Kramar said. “But it’s a matter of where the worst of it sets up. Whoever gets it, is going to get a lot of rain.”
For the latest weather projections, see Weather.gov/PBZ .
Patrick Varine is a Tribune-Review staff writer. You can contact Patrick at 724-850-2862, email@example.com or via Twitter @MurrysvilleStar.