I'm very excited about the Michelin GT Challenge next weekend, as I'll be at the race, providing weather information and consulting to track officials. I've been watching the weather closely for next weekend, so I figured I'd make a post to share what I've been seeing. There has been relatively good model agreement on the general weather pattern for next weekend, but this far out, the finer details remain hazy.
Late in the week, a cold front will be approaching from the west, and will be located near the Appalachian Mountains on Friday. This front will be the main player in the weather for VIR over the weekend. The question will be how far south and east this front can push, and how much precipitation will form along it. Here's a sequence of maps that show where the front might be positioned on Friday, Saturday, and Sunday:
The position of that high will probably bring some warmer and more humid air for the weekend (compared to earlier in the week), with highs in the upper 80s, and dewpoints in the upper 60s to lower 70s.
A couple of caveats:
1) There may still be enough instability to the south of the front for isolated to scattered showers and thunderstorms in the Piedmont region on Saturday and Sunday, even if the front stays well north. However, models do not do well with forecasting instability levels this far out in time. So although the probability of rain at the track is low at this time, it is still a possibility.
2) Only a slight shift in where the front is located might make a big difference. If the mid-level high is weaker and the front stalls across southern Virginia, the potential for rain will be higher.
Taking these factors into account, I'd put the chance of rain right now between 10% and 30% both days.