Friday will likely begin with mostly cloudy skies, and possibly a few showers in the area. But through the day, the coverage of showers and thunderstorms will be increasing, making the afternoon the most likely time for storms to have an impact. The hours between 3 pm and 7 pm appear to be the most likely time. With high moisture content in the atmosphere, these storms could produce very heavy downpours. Rain amounts between a quarter and a half inch are expected, although it is possible for a strong storm to drop a half to one inch if it moves directly over the track. Storms may also produce frequent lightning and gusty winds of 30 to 40 mph.
On Saturday, a low pressure system to the west of the Appalachians will continue to trek northeast, so it will have less of an impact on the NC/southern VA region. However, there will still be a southerly flow of moisture into the region, so scattered showers and thunderstorms are expected again in the afternoon. If a storm moves over the track, there could be some wet racing, but these storms should be weaker and shorter-lived than on Friday. A tenth to a quarter inch of rain will be possible.
With the low pressure system moving farther away, Sunday is expected to be mainly a dry day. With afternoon heating, some storms may develop over the mountains to the west, and these may gradually move eastward. I can't completely rule out a shower reaching VIR late in the day, but I think it will be late enough that it won't have an impact on the racing. There will be more sunshine on Sunday, so highs will reach the upper 80s.