By Doug Schneider

The main change to the forecast today has been to add a mention of a light sprinkle or shower on Sunday morning.

A west to northwest flow will bring the marine layer into the Monterey Peninsula each night, resulting in low clouds forming. These clouds will linger through the morning, and dissipate by noon, leaving mostly sunny skies on Friday and Saturday afternoons. On Sunday, the moisture will get a little deeper as a cold front approaches from the northwest. This could squeeze out a little rain, probably just a couple hundredths of an inch at most. Rain could fall during the Sunday morning warm-up session, but again, the light nature of the rain should not have much of an impact. For the race, it will be partly sunny with temperatures in the 60s.

By Doug Schneider

Aside from some clouds and fog each morning, nice weather is expected for IndyCar's visit to WeatherTech Raceway Laguna Seca. 

All this week, a large area of high pressure will be located off the California coastline. This high will produce a west to northwest flow off the Pacific Ocean. In this setup, it is common for the Monterey Peninsula to experience fog and low clouds overnight due to the marine layer - moist air off the ocean spreads inland, and as temperatures cool overnight, fog can form. This past weekend at the IMSA event, fog and low clouds formed each morning, and usually cleared out between 10 am and noon. I expect a similar pattern this weekend. Some of the early morning sessions may be impacted due to low visibility. ​Once the clouds and fog lift, sunny skies will prevail. Thanks to the cool air off the ocean, temperatures will only reach to around 70 degrees in the afternoons. 

By Scott Martin

Other than a few tweaks to the temperatures and dewpoints, the forecast remains the same for the Grand Prix of Portland. Both days will start off mostly cloudy, but clouds will decrease throughout each day and skies will become mostly clear by the afternoon hours. Highs will top out in the mid to upper 70s.

By Scott Martin

While there will be plenty of excitement on the track at Portland International Raceway, the weather department will be rather uneventful as the forecast is really similar for each day of the event weekend. Each day will feature a mix of sun and clouds, with temperatures starting off around 60 degrees in the morning and topping out in the lower to mid-70s. Winds will be out of the northwest ranging from 2-8 mph, and we'll remain dry throughout the weekend.

By Doug Schneider

Today, some scattered to isolated showers and thunderstorms will be possible in Middle Tennessee. There is only a slight chance of one of the showers passing over the downtown area, so I have the chance at 20% with a low impact. A dry day is more likely. With mostly cloudy skies today, temperatures will peak in the mid 80s.

More sunshine is expected Saturday and Sunday, which will bring afternoon temperatures into the 90s. With a high pressure ridge building over the area Saturday, showers are unlikely. 

I'll be a the race starting this afternoon, and I'll try to post weather updates on Twitter if necessary. Follow @RacecastWx. 

By Doug Schneider

I expect that the weather will cooperate for the inaugural Music City Grand Prix in Nashville, Tennessee. No rain is expected at this time, and although temperatures will be warm, the humidity won't be oppressively high. For Nashville in early August, it looks pretty good.

Through much of the middle portion of the week, there will be a broad upper level trough over the eastern U.S. with a few small troughs that ride around the larger trough. The main impact of this trough for Middle Tennessee will be to push the deep moisture east of the Appalachian Mountains, and keep temperatures fairly cool in Nashville. A secondary trough passage will occur on Friday, but there will be a lack of moisture that makes the chance of rain very low. Friday will have some partial cloud cover, and there is one model that generates some rain, but at this time I think a dry day is most likely. 

Nashville will be on the west side of the trough on Saturday, which will keep dry weather and mostly sunny skies in the forecast. With a high pressure ridge slowly building in, temperatures will trend upward into the lower 90s by Sunday. Humidity levels will be rising too, but dewpoints are expected to be in the upper 60s to near 70, which could be much worse for this time of year in Nashville. The normal high for Nashville this time of year is around 91, so we should see highs in that neighborhood. 

I'll be attending the race this weekend. As a resident of Tennessee, it's exciting to have a race in my home state!

By Doug Schneider

Good news with today's forecast update for Indycar at Mid-Ohio - dry weather is expected each day, with comfortable temperatures. 

The latest models have shown a pattern that is a little faster than earlier in the week. An upper level trough will be crossing Ohio on Thursday night, and will be southeast of the area by Friday. This will usher in a northerly flow with drier air that will keep dry conditions all day. There will be some scattered clouds, and with a northerly wind at 10 to 15 mph, temperatures will be mainly in the 60s during the day, peaking around 70. 

High pressure will be drifting east across the region through the weekend, providing mostly sunny skies and gradually warming temperatures. Highs on Saturday will be in the mid 70s, then lower 80s on Sunday. Overall, a great weekend to enjoy some great racing.

By Doug Schneider

An unsettled weather pattern will be over Ohio during the middle of the week, but gradual improvement is expected over the weekend, which is expected to result in nice weather for race day.

A front will be stalled across Ohio on Thursday, which will bring quite a bit of rainfall. By Friday, that front will push south and east of the track as an upper level trough pushes south across the Great Lakes. So although the front will be clear of the area, the presence of the upper trough will mean a few scattered showers will remain possible on Friday. I think any showers should be light, having low impacts on the practice sessions. It will be cool as northerly winds behind the front bring cooler air to the region, with highs only in the lower 70s.

Saturday is the most uncertain day of the forecast as the upper level trough will slowly push southeast. The question is how quickly it will exit Ohio, and different models have different answers to that. With the trough expected to be somewhere nearby, there could be some isolated afternoon showers that develop. However, any showers that might develop are expected to be brief and light, with little to no impact. With a little more sunshine expected than Friday, highs will reach the mid 70s. 

By Sunday, I expect that the upper trough will be clear of the area, although there are some models that keep it over Ohio and produce some showers. I think the most likely scenario is that Sunday is dry with partly cloudy skies.