The Roanoke Times is soliciting some memories and lessons learned from the derecho, which occurred a year ago Saturday (June 29 was a Friday night last year). Be sure and click on this link if you wish to share one, or read others.
I’m not going to bother posting another inset Storm Prediction Center risk map here because it will mostly likely change by morning. Southwest Virginia was in the slight risk area Friday as of Thursday evening. Click here for the latest from SPC. Whereas winter weather forecasting is very difficult in the vertical — minor differences in temperatures at various layers have huge changes on the surface weather — severe weather forecast is often intensely difficult in the horizontal, as outflow boundaries, areas of subsidence (sinking air behind precipitation, limiting convection), cloud cover and subtle disturbances can shift severe risk zones hundreds of miles across the map in a few hours, sometimes. It’s like a chess game in which every move changes the shape of the board. On Thursday, morning rain and clouds put the kabosh on the needed instability for afternoon storms. But Friday will be a brand new day. Keep an eye out for potential showers and storms to develop during the day.
And for that matter … much the same will be possible just about every day into the foreseeable future, which is about a week. It appears the dipping jet stream trough will gradually nudge a bit farther west, into the central U.S. Our region won’t be in the core of cooler air, that will be west of us, so it looks like our Fourth of July week cooldown will be a bit more muted. Instead, the counterclockwise circulation around the upper-level trough in the south-central U.S. will keep funneling Gulf of Mexico moisture into the East, especially the Southeast coast, much of the next 7 days. The Weather Prediciton Center shows Southwest Virginia getting more than an inch over the next 7 days — I wouldn’t be surprised if that ends up being more in some spots. This will come in showery and occasionally stormy periods, not constant rain, so there will probably be several periods of sunshine interspersed with the showers through much of the next week — and don’t presume fireworks displays to be a washout this far away. Late next week, the low may weaken and move out, allowing some high pressure to build back in with a bit hotter weather. With the heat dome firmly entrenched in the West — some talk of near-world-record mid 130s in Death Valley — and so much moisture present in our ground and in our air, a major heat wave looks unlikely to build in at least through mid-July, and there may be additional jet stream dips with some cooler air pushed down by that western heat dome. Looks like we’re continuing the same basic pattern of mostly near-normal temperatures, sticky days, and periods of showers and storms, some of which could occasionally be severe.