By Doug Schneider

The chance of weather impacts at WWTR this weekend is falling from the previous forecast. There's still a chance of seeing showers and thunderstorms in the area on Saturday afternoon, but coverage is expected to be scattered. There could be some delays to sessions, but it doesn't look like a washout on Saturday. On Sunday, I expect dry conditions, although there are some models that show isolated showers around in the evening. I'm going to be optimistic, as I think the chance of impacts to the race is very low, and have a dry forecast for the race. Temperatures during the evening race will be starting in the mid 80s and falling through the lower 80s to upper 70s by the checkered flag.

By Doug Schneider

The chance of rain has shifted earlier with the latest model data. The general pattern remains the same as my original forecast, with a low pressure system moving north of France across Great Britain over the weekend. The timing of rain with the approaching cold front has moved into Friday. Friday will still be a warm day, until showers and possibly a thunderstorm moves through in the afternoon, cooling down the temperatures. Once the front moves through, temperatures will be cooler for Saturday and Sunday. A lingering light shower cannot be ruled out Saturday morning, but it should not impact the race. The entire 24 hours of the race is still expected to be rain free, with pleasant temperatures.

By Doug Schneider

A slow-moving upper level low pressure system will be the main weather feature that will impact the St. Louis area this weekend. How quickly this low moves east will determine the impacts for the race on Sunday evening. The models are showing this low right over the area on Saturday, which makes it likely that the practice and qualifying sessions will be affected by showers and thunderstorms at times. It does appear that the rain will mainly be light and on/off, so there may be windows of opportunity to get some dry running done. Sunday's weather depends on the speed of the system. At this time, it appears that the most likely scenario is that the low brings numerous rain showers on Saturday, and exits by Sunday morning, leaving dry conditions for the evening race. However, if the system ends up being slower than currently shown by the models, then the chance of rain may extend into Sunday evening and impact the race. 

By Doug Schneider

The main weather feature that will affect France later this week is a low pressure system over the northern Atlantic. This system will start well away from the northwest coast of France, then track slowly northeast through the weekend, ending up north of Scotland by Sunday. Ahead of this system on Wednesday, Thursday, and Friday, temperatures will be quite warm, reaching the 80s and 90s F (30s C). A weak upper level disturbance will cross northern France on Thursday morning, bringing scattered light showers and cooler temperatures with increased cloud cover. Friday will be hot with mostly sunny skies and highs in the lower 90s F, mid 30s C. As the low pressure system gets closer, it will push a cold front across Le Mans that could bring some showers on Saturday morning. This far out, the timing is uncertain, and how much rain falls is still unclear. There could be wet conditions to start the race. Once the front moves through, the rest of the race should be dry with cooler temperatures. 

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By Doug Schneider

Most of the Detroit Grand Prix event will have very nice weather, with dry conditions and pleasant temperatures expected for Saturday and Sunday. This will be due to a cold front that will move through the area Friday evening. The timing of this cold front will be the question for whether there are showers that affect the on-track activity late Friday. Most of Friday will be nice, but there is a slight chance (20%) that showers could arrive in the area before sunset, and affect some late afternoon sessions. It appears that if there is rain Friday afternoon or evening, it will be light. Most of the rain associated with the cold front will come later in the night. Saturday will be a little breezy behind the front, with a northwest wind between 10 and 15 mph, with some gusts up to 20 mph.

We have a pleasant weekend of weather for the Monaco Grand Prix as a High pressure system with a loose pressure gradient will be laying over the region. This will keep cloud coverage low and humidity levels down along with mild temperatures throughout the day. There are hardly any rain chances for the weekend as well, so we should see a pretty clean race for Monaco standards. This track already does not allow much overtake so without volatile weather conditions, qualifying is going to be very important for the result of race day.

By Doug Schneider

I've been taking some heat on social media for my dry forecast for the Indy 500. I've had people pointing at their weather apps, showing me how their apps said it would be raining on Sunday. With today's update, I'm sticking with a dry forecast, and here's why:

The pattern for the weekend will have a low pressure system nearly stationary over New England, with a high pressure system over the northern Plains and south-central Canada. This will create a northerly flow across Indiana. A front will be located near the Ohio River, across Kentucky and through Missouri. This front will be the focus for rain over the weekend. With the northerly flow across Indiana, I expect the front and moisture associated with it to stay south of Indianapolis. There were some models that had this front farther north with previous runs, but the latest model runs are coming into better agreement that it will stay to the south. 

Some weather apps will use a blend of models, or an ensemble, for their forecast. While a model blend is good to use in some situations, it will sometimes tend to overdo the aerial coverage of rainfall as different model rainfall depictions get smoothed together. Most models may be dry at one location, but a few wet models will get blended together with them and increase the chance of rain at that location. A human forecaster can recognize these situations and mentally correct for the models using experience and pattern recognition.

This forecast can certainly change before we get to Sunday. A lot can change in the models between now and then, and I'll post another update if necessary. For now, I think a dry day is the most likely scenario. 

By Doug Schneider

​The weather looks spectacular for this year's running of the Greatest Spectacle In Racing, the 109th Indianapolis 500. A large high pressure system will be over the northern Plains and south central Canada on Friday and drift slowly east through the weekend. This will provide cool and dry conditions each day. There could be a bit of a breeze on Friday with gusts from the northwest up to 20-25 mph, but otherwise no weather impacts are expected.