UPDATE 9:15 PM, 8/5: Downpours at Blacksburg epitomize continued pattern of rainfall have-a-lots and have-nots
UPDATE 9:15 PM, 8/5: As radar shows tonight, a broad area of showers and storms slowly moving across western Virginia is creating more haves than have-nots in terms of rain, and a few have-to0-much spots, with a flash flood warning toward the North Carolina line in part of Grayson and Smyth counties. The rain will slowly diminish overnight, but perhaps a few dry spots can get some wetness, in addition to the repeated weekend downpours in the Blacksburg area. END UPDATE
The image at left is a close-up focus of the larger National Weather Service Doppler radar rain estimate from midday Friday through late Saturday evening. One spot stands out — the little patch of yellow and orange amid darker greens very near Blacksburg. While the National Weather Service office may have only gotten a half-inch total the last couple of days, the orange dot indicates locally 4-inches plus. This radar shot is an estimate, but a couple of Weather Journal commenters in the last thread reported 1.75 to 3 inches near the eastern side of the Blacksburg. Elsewhere, there are a few other locally heavy spots near Fancy Gap, west of Interstate 77, and east of Lynchburg. There is also Roanoke’s interesting color shade in which rain to east/dry to west was almost perfectly divided by U.S. 220/I-581 — I got caught in this downpour in south Roanoke, watching sheets of rain blow in while my house a couple miles away got nothing. But the Blacksburg area just happened to be in the bullseye of slow-moving, torrential rain dumpers each of the past two days, Saturday’s storms likely building on left-over pooled moisture and outflow boundaries from Friday’s storms.
Sunday’s weather is likely to again create have-a-lots and have-nots in regard to rain. Steering currents aloft are weak, and moisture is thick, so once terrain effects, upper-level impulses, outflow boundaries and daytime heating cook up storms, they won’t move much, and will put down a lot of rain in small areas very quickly, while others not far away just hear a rumble and see some dark clouds and get nothing. A diffuse cold front is working in from the northwest, and that will likely enhance storms especially west of Roanoke by late Sunday and Monday.
The week ahead looks sticky with highs mostly in the 80s and continued periods of scattered showers and storms. Extreme heat is likely to stay far to the west, but cooler, drier air will stay mostly in Canada, for now. So we’ll be stuck with tropical, sticky stuff, with no highs above 100 and very few lows dipping below 60, excluding high elevations.
There are three areas of disturbed weather to watch in the tropics. The weak disturbance east of Florida may kick a little moisture our way next week. Tropical Storm Ernesto has a good chance to end up in the Gulf of Mexico later this week. There are big questions about whether Tropical Storm Florence will make it across the big pond at all.