A few strong to severe storms crackled early Wednesday evening as a cold front pushed southward into Southwest Virginia. Two of the strongest storms tracked over Blacksburg (many hail reports, 1/2 to 1 inch in diameter) and over the northern and western parts of the Roanoke Valley, where tents were blown down at the Roanoke Valley Horse Show in Salem … again, as they were a week ago Thursday in the “Son of Derecho.” The storm that moved into the Roanoke Valley was interesting for me to observe as it did seem to have some supercell-like structure for a time, with notable lowered, rounded cloud masses (such as the one pictured passing west of downtown at left), inflow winds for a time and storm structure a little more defined than most summer storms we get here in the mountains. Boundaries of clashing air masses often create horizontally rotating air aloft that can become drawn into the updrafts of storms and create some weak rotation, before the downdrafts of the storms take over and the storms become “outflow-dominant.” By the time this storm punched Salem, it was outflow-dominant with considerable wind and a voluminous downpour of rain.
The air behind the front will be cooler and somewhat drier today and Friday, with highs only in the 70s to low 80s. We can’t entirely rule out some scattered showers and maybe even a few thunderstorms today, as lingering moisture banks against the mountains, with the best chances the farther southwest from Roanoke you are. We are beginning to enter that long period of stagnant upper air winds I was talking about yesterday. Fronts to the west are not going to get the push they need to affect us, but moisture and even some disturbances drawn in from the Gulf of Mexico and Atlantic may be able to stir up showers and storms at times as the warmth nudges up early next week. Don’t expect a heat wave next week … just 80s-low 90s and sticky with a few rumbles and downpours here and there, now and then.