A large high pressure ridge will be centered to the southwest of Connecticut, near the Ohio River and Kentucky. This ridge will remain nearly stationary through the end of the week, and provide a southwesterly flow of warm and humid air into Lime Rock. On Friday, there is a slight weakness moving across the top of this ridge that is expected to spark some showers and thunderstorms in the Mohawk Valley region of New York in the afternoon. These storms will track to the east-southeast, and may reach the Lime Rock area late in the day. The final practice session of the day is held from 4:55 to 5:55 pm, and it will be close as to whether storms reach the track by the time it ends. I think it is more likely that they arrive after 6 pm, so I have kept the Impact at a Green Flag.
Temperatures and humidity will continue to climb on Saturday, and the combination of heat and humidity will make it feel like it is over 100 degrees. The atmosphere appears a little more stable on Saturday, so any chance of showers and thunderstorms is unlikely.
If you're at the track either day, drinking plenty of water will be a must. Alcoholic beverages won't keep your body adequately hydrated. Take frequent breaks in the shade and use sunscreen.