Flash flooding possible Tuesday afternoon, later in the week
The National Weather Service has issued a Flash Flood Watch for the Pittsburgh region starting Tuesday afternoon, when the first of several strong rainstorms is expected to rapidly roll through.
Meteorologist John Darnley said the storms Tuesday afternoon are expected to affect the northern parts of the region and can quickly drop between an inch and one-and-a-half inches of rainfall, overwhelming streams, storm sewers and soil to create flash-flooding conditions. Another wave of storms is expected in the evening, bringing at least another inch to the more southern parts of the Pittsburgh region, he said.
"They roll through kind of fast but they drop a lot," Darnley said. "The ground and the storm drains get overwhelmed."
The Flash Flood Watch, where conditions may exist for flash flooding and landslides, takes effect at 1 p.m. for parts of Western Pennsylvania, Western Maryland and West Virginia. The weather service warned the storms could also bring strong winds and large hail, and will put out more information later on whether the "watch" gets upgraded to a warning.
Periodic showers & tstms today-some severe w/ large hail & damaging wind. A Flash Flood Watch has also been issued for part of the area. Latest radar available = https://t.co/R38AcFOdTY . Latest forecasts/watches/warnings = https://t.co/JWLI3e1waM , or https://t.co/nR4yhzDSj7 . pic.twitter.com/pBJNgJX6O2— NWS Pittsburgh (@NWSPittsburgh) May 15, 2018
Meteorologists blame a frontal boundary , with warm temperatures and humid air to the south of it, for creating repeated rounds of strong storms as it lingers over Western Pennsylvania. The weather service said it even spawned a tornado or two in Somerset County Monday evening.
Storms were a possibility for every day this week, though Darnley said their strength may abate Wednesday and Thursday before picking up steam again Thursday into Friday.
"Wednesday and Thursday don't look so bad... There will be more intermittent, more shower-y storms," he said.
But the chance of flash flooding will increase again Thursday night and Friday as more strong storms dump rain into an already-saturated system, he said. The growing season is some small help — living plants will suck up and retain some of the moisture, Darnley said.
He did not anticipate river flooding to be an issue this week. Though river levels are high, the greater risk will be debris washed into the rivers, especially for small boats.
Matthew Santoni is a Tribune-Review staff writer. Reach him at 724 836 6660, firstname.lastname@example.org or on Twitter @msantoni.