By Doug Schneider

The weather continues to look great for the 25 Hours of Thunderhill. The only weather impact may be some windy conditions on Thursday for the testing sessions. Winds from the north will be sustained at 15 to 25 mph, and may gust to around 30 mph at times. It will still be breezy on Friday, but not as windy, with winds between 10 and 15 mph most of the day. Temperatures for the start of the race will be mild for Northern California this time of year, reaching the mid 60s by the afternoon. On Sunday, an upper level trough will be approaching, and it may bring a few more clouds. But any rain associated with it will not arrive until long after the race is over.

By Doug Schneider

The final major sportscar race of 2016 is upon us. This year seems to have flown by for me. It's been a terrific year of racing in so many series, and Scott and I thank you for following our forecasts. We will be back again next year, continuing to combine our love for weather and racing here at Racecast Weather.

Simply put, the weather looks good for the USAF 25 Hours of Thunderhill. There will be a cold front that is expected to move across Northern California Wednesday night; however, no rain is expected at Thunderhill with the front. Any rain associated with the front should remain well to the north and east. Behind the front, it will become quite windy on Thursday, with a north wind at 15 to 25 mph bringing chilly temperatures in the 40s and 50s through the day. 

For the rest of the weekend, a large high pressure system will be over the east Pacific Ocean. It will provide dry weather and abundant sunshine at Thunderhill Raceway as it builds toward the east. Temperatures will gradually warm a little through the weekend, and highs on Saturday and Sunday afternoons will be around 60. Chilly temperatures in the 40s are expected Saturday night, with temperatures between 55 and 60 by the end of the race at noon on Sunday.

By Doug Schneider

No big changes were needed to the forecast at Daytona this weekend as Trans Am will have great weather for its season finale on Saturday. Friday's qualifying sessions will have full sunshine and highs in the upper 70s. Clouds will start to increase through Saturday as winds shift to the northeast, bringing more moisture off the ocean, but no rain is expected during the day. There is a slight chance of some light showers beginning Saturday night and into Sunday for the historic racing event. Winds will be picking up too on Sunday as a low pressure system takes shape off the coast. 

By Doug Schneider

The finale of the Trans Am season should have great weather in Daytona this weekend. 

A cold front will move through the area on Wednesday night, and there is a chance of some showers ahead of the front as teams arrive at the track on Wednesday. But once the front moves through, there will be plenty of sunshine and comfortable temperatures. Thursday will be a little breezy behind the front, with a northeast wind of 10 to 15 mph, gusting to 25 mph at times. Temperatures will warm into the upper 70s on Friday, with lighter winds as high pressure builds in. There will be another cold front approaching from the north on Saturday, but it will only increase clouds a little bit, and lower temperatures slightly. There will not be enough moisture for the front to produce any rain as it moves through, so I'm not worried about any rain for the race. 

I'll have another update on Thursday, unless there is a significant change to the forecast before then.

Showers and thunderstorms are likely at COTA today, which may interrupt the scheduled practice sessions. A front will be moving into northern Texas late in the day, and push southward overnight. Compared to what was shown by the models on Monday, the front is moving a little slower, so I've added a slight chance of showers and thunderstorms on Friday. 

There is some uncertainty about what will happen with the front on Saturday. I'm going with the models that show the front pushing through and being located south and west of COTA, which should mean a dry race day. But there is one model that is keeping the front near the track on Saturday, and producing some showers. I'm not confident enough to jump on that model yet. It does look like there will be more clouds than sun for the race, with comfortable temperatures in the upper 70s.