Roanoke has flirted with the 90-degree mark each of the last three days, with highs of 89, 88 and 88 on Tuesday through Thursday, respectively, but the mercury hasn’t topped the 90-degree mark since Aug. 8. That’s likely to change Friday, the last day of “meteorological summer,” which runs June 1-Aug. 31 for data convenience. We’re going to get a one-day heat spike somewhat similar to July 26 — a 98-degree day surrounded by low 90s highs on either side — though not quite as intense. Warm, dry high pressure will build overhead, and winds will slowly switch around to the west, introducing a weak downslope flow along and east of the Appalachians. Downslope winds warm up and dry out as they compress. Roanoke and points south and east will likely see low to mid 90s, with widespread mid-upper 80s in most other parts of Southwest and Western Virginia below about 3,000 feet in elevation. The one thing that could stop the heat spike in a given location would be a well-placed isolated shower or storm — that can’t entirely be ruled out, but it appears the stagnant, dry air with the high will limit shower/storm development on Friday.
Speaking of the end of summer, Labor Day marks the end of our nation’s cultural summer, which begins with Memorial Day. This Labor Day may well be similar to last Labor Day — a chance of heavy rain resulting from the inland track of a tropical system. The remnant low of Tropical Storm Lee soaked us with 2-5 inches of rain last Labor Day, with some locally heavier amounts, and a tornado that damaged a gas station at Cana in Carroll County. Fast-forward a year, and there are growing indications that what’s left of Hurricane Isaac, teaming up with a slow-moving, perhaps stalling, cold front, will rain on our Labor Day once again — including a jam-packed Lane Stadium for the Virginia Tech-Georgia Tech football game. Rain projections have slowly been increasing — now 2-3 inches forecast in our region through late Tuesday, with 7+ inches possible in the Ohio Valley — as the forecast track of Isaac’s remnant, slowly dying low has been nudged south and east. The exact point at which this remnant low is located, or whether it even exists at all, may not matter much by Monday, certainly mattering less than (1) how much of Isaac’s tropical moisture will be squeezed out by the front and disturbances moving along it and (2) how much additional moisture it can draw ahead of it on south and southeast winds before it dissipates. Unlike most tropical systems we deal with, bee-lining at us from the Gulf or Atlantic coast, effects arriving within 24-48 hours, it will probably be late Sunday before we see much impact from Isaac’s remnants, 4 or more days after landfall. Moisture will be gradually increasing, though, with chances of scattered showers and storms slowly picking up on a warm, sticky weekend with highs in the 80s to low 90s and lows in the 60s.