UPDATE 7:10 PM, 8/17: Roanoke’s high of 72 was 1 above record lowest high for date. Blacksburg’s high was 68 — both are 14 degrees below normal. The drizzly, rainy wedge is here, and will likely hang around well into Sunday, with similar temperatures. Next week may provide a return to more typical summer temperatures, with highs in the 80s, possibly some low 90s. END UPDATE
UPDATE 2:10 PM, 8:17: Mid-afternoon high of 71, bolstered by morning peeks of sun, means today can only tie record for coolest August 17 high temperature at Roanoke, but only if clouds hold off any additional warming. END UPDATE
UPDATE 8 AM, 8/17: The cloudy, drizzly, rainy weather expected this weekend is arriving just a bit slower than earlier expected, at least from Roanoke north and west. But it’s on the way, with showers already poking into Southside Virginia and several reports of dense fog south of the Roanoke Valley. Dankness delayed slightly, but not denied. Depending on how long the sun is out in Roanoke this morning, a record for lowest maximum temperature for August 17 is still possible at Roanoke (previous record 71, as mentioned below), but hours of sunshine would make that much less likely … but might spare a decent Saturday at many locations. END UPDATE
A historically wet summer gets a little wetter this weekend, which in turn may contribute to a historically cool mid-August Saturday. Moisture and clouds are expected to begin overspreading Southwest Virginia overnight and early Saturday as high pressure to the northeast keeps surface winds out of easterly trajectories, and a disturbance moving through increasingly southerly flow aloft lifts Gulf of Mexico moisture from the south. The arrival of this moisture falling through somewhat drier air and the angle of the winds are expected to create a “wedge” effect that traps cool air over our region on Saturday such that high temperatures will not move upward too much from morning low temperatures. Roanoke has never had an August 17 with a high cooler than 71 degrees since the start of official records in 1912, but Saturday likely will be the first, with highs possibly not climbing out of the mid 60s. Blacksburg’s coolest high for August 17 was 63 in 1964 — it’s not out of the question that mark will fall, though it probably will get a tad warmer. Rain coverage will increase throughout the day from south to north, so morning hours on Saturday will be best for any outdoor activities, and likely linger through the night into Sunday.
Rain amounts are not expected to be large over the entire weekend, mostly under an inch, but any amounts will add to historic summer rainfall totals. Since June 1, Roanoke has had 20.15 inches of rain, only the fourth 20+ inch summer on record and the first since 1949. At 40.89 inches through Friday, Roanoke only needs 0.36 inch to equal its annual normal precipitation of 41.25 inches. Blacksburg stands at 16.56 inches for the summer, ranking fifth since records began in 1952, and less than 3 1/2 inches from the top spot. With 38.43 inches since Jan. 1, Blacksburg is also only within 2 1/2 inches of its annual normal precipitation of 40.83 inches. Both Roanoke and Blacksburg are actually nearly an inch BELOW normal for rain to date in the month of August.