UPDATE 10:50 PM: Showers and storms have rapidly developed this evening along the Interstate 81 corridor. Very heavy rain is possible in any of these cells … the flash flood watch continues until 8 a.m. Lynchburg was hammered by torrential downpours earlier today, similar to those experienced in northwest Roanoke on Thursday, leading to many closed roads. There are growing indications the approaching cold front will NOT be able to push out the tropical moisture, with more showers and storms occurring intermittently over the weekend. Will post a new blog entry in the next couple of hours. END UPDATE
UPDATE 2PM: The National Weather Service in Blacksburg has determined that Wednesday’s deluge of more than 3 inches in an hour at the Roanoke Regional Airport was between a 200-year and 500-year event. Scattered and showers and storms are starting to develop this afternoon. A flash flood watch continues with some locally heavy downpours possible. END UPDATE
Here we go again. A flash flood watch takes effect at 10 a.m. for most of our region continuing through the evening and overnight, though cut off a bit to the west (Bland, Tazewell and Smyth counties westward are out of the watch) and extending much farther eastward. It’s the same song, second verse as Wednesday … clusters of storms developing in the afternoon as the result of thick moisture, lift from a cold front and daytime heating, modest though it may be with lots of clouds. Just as Wednesday, while most locations will get an inch or less of rain, some much less, there will be spots that get more than an inch very quickly. With ground extremely saturated by what is now the wettest July on record at Roanoke at 10.32 inches with still three weeks left, runoff will be rapid where it rains the hardest, and flash flooding can occur. So keep an eye to the sky and radar today, and try to not be near creeks, streams and flood-prone roadways if you think heavy rain is about to occur. Severe storm risk will be limited by weak winds aloft, but a few “wet microbursts” with very localized strong downdraft winds are possible.
It pains me to say the weekend is now looking murkier than it did. We will likely get a break from the rain for some period on Friday, but the front may not make as much progress southeastward as just about everyone hopes. By Saturday, there may be a return flow of moisture off the Atlantic that could lead to some upslope-enhanced showers and thunderstorms. It’s so hard to clear out the surface moisture entirely in July.