The Mon Wharf is closed to parking today by rising water that is extending a flood advisory to Saturday afternoon.
The National Weather Service in Pittsburgh based in Moon amended its previous alert that predicted the Ohio River could crest at 18.5 feet -- it now expects the river to reach 20.8 feet by tomorrow morning, which will affect the entire Wharf. Water reaches the 10th Street Bypass when the river rises to 22 feet, but meteorologists think it will stop short of that.
Allegheny County emergency dispatch supervisor confirmed there were trees down at Geyer and Kenneth Drive in Shaler affecting traffic. Other fallen trees have been reported in Fox Chapel and in Plum, downed from overnight winds and wet soil that cannot offer sufficient support.
Over the past 10 days, the Pittsburgh region experienced a large air mass of cold weather, said Brad Rehak of the National Weather Service. When that moved out, it allowed a storm system to move up from the Great Plains, bringing warm air from the Gulf of Mexico. As it moved out yesterday, another cold air mass from central Canada that was preceded by heavy rain set in.
"You get a lot of this yo-yo-type stuff in winter," he said. "The extremes between the hot and cold is a little unusual but it happens."
It was 59 degrees in the Pittsburgh region about 7 a.m. Wednesday. At the same time this morning, temperatures fell to 29 degrees. The weather service does not keep track of record drops, but meteorologists say such an abrupt temperature change is unusual.
"This is relatively rare thing we're having," National Weather Service meteorologist Lee Hendricks said.
Snow showers were moving across the region this morning won't amount to much. But the weather service advised drivers to be alert for bands of snow that could accumulate as much as a half-inch and significantly reduce visibility in a short period of time.
One snow band near the I-376 interchange in Moon reduced visibility to almost zero early this morning, Mr. Hendricks said.
Molly Born: email@example.com or 412-263-1944 or on Twitter @borntolede. First Published January 31, 2013 12:30 PM