By Doug Schneider

Rain showers will start to spread into the Le Mans area beginning tonight. Periods of showers are likely to continue through Saturday as a low pressure system sits over the Bay of Biscay. The most likely period for showers on Saturday will be in the afternoon and evening, during the opening hours of the race. There could be around a quarter of an inch (around 6 mm) of rain that falls on Saturday. 

Saturday night should have a lower chance of showers in the area. Coverage will be more scattered, and showers will be lighter. The threat of thunderstorms will also diminish. Scattered showers will continue around northern France through Sunday, and there may be some breaks in the clouds that allow some sun to briefly shine through. 

I will be travelling on vacation with family tomorrow, so I won't be able to post radar updates as I usually do. I recommend this site to monitor radar - https://www.meteo60.fr/radars-precipitations-pluie-france.php

By Doug Schneider

Not much has changed in the forecast for Le Mans with the latest data. Some things have come into better focus, such as the timing of the best chance of rain and potential rainfall amounts. 

High pressure over the British Isles will keep conditions dry and mild at Le Mans on Thursday, with mostly sunny skies. Clouds will start to increase a little on Friday as the high pressure system moves east and a low pressure system off the northwest coast of Spain approaches. As this low moves into the Bay of Biscay, it will start to bring a chance of rain into northern France, beginning Friday night. There is good agreement between the models that the center of the low will be just off the west coast of France on Saturday, sitting nearly stationary through the day. Shower and thunderstorms will be numerous across eastern and northern France all day, but the most likely time for showers to occur at the track will be in the late afternoon and evening - near the start time of the race. The rain could be briefly heavy if a storm moves directly over the track, with a quarter to a half inch of rain possible (6-12 mm). There could be a possibility of a caution period or a stoppage if the heavy rain and lightning occurs. 

The threat of showers will drop Saturday night, but it won't completely go away. There may be some scattered showers lingering around overnight and into Sunday morning. The chance of rain on Sunday looks lower than Saturday as the low pressure system is expected to weaken and drift southeast. Any showers on Sunday should be lighter as well, so the impact on the racing is expected to be less. 

By Doug Schneider

Warm temperatures and mostly sunny skies are expected at Le Mans through most of this week, but as we approach the weekend, the chance of rain still start to increase, and there's a good chance of seeing rain at some point during the race.

A large high pressure system will be drifting east from England to Scandinavia from Wednesday through Friday, providing dry weather and warm temperatures across northern France. A low pressure system will be tracking east across the Atlantic, and be located somewhere near the Bay of Biscay by the end of the week. This low pressure system will spread increasing moisture into France over the weekend. The chance of rain is a bit uncertain this far out, and it will depend on the exact position of this low, which isn't yet clear. If it tracks farther south as some models suggest, there will be a lower chance of rain. A more northerly position of the low will increase the rain chances. In this forecast, I have taken a middle ground, with rain chances in the 40-50% range. This may go up or down with later forecast updates, so check back through the week.

By Doug Schneider

Each year at Racecast Weather, we collect photos through the year of our two favorite things - weather and race cars - and pick the best to be featured in a final post to close out the year. Thanks to the extremely talented photographers (and not so talented, like myself) who took these photos - credit for each pops up when you hover over each image. Click on each image to view a larger size.

Thanks for following our forecasts through 2019, and Scott, Stephen, and I hope you have a very happy Christmas season. We'll see you again on December 30 with the forecast for the Roar Before the 24 in January.

By Doug Schneider

Click on images to enlarge

The start of the 24 Hours of Le Mans will be covered by clouds as an upper level trough and a surface cold front will be moving toward the area. Here's a look at the radar and satellite image at 1:30 pm:

Although the rain over Brittany is moving east and looks pretty solid now, it is expected to break up more as it approaches Le Mans. So I don't expect it to have much impact. If there is a shower this afternoon, it will be very light and short-lived. There may not even be enough to measure, maybe just a trace, which wouldn't even require a change to rain tires. 

Clouds will be decreasing in the evening, with partly cloudy skies by sunset. Temperatures overnight will fall into the upper 50s F or mid teens C. Mostly to partly cloudy skies can be expected from sunrise tomorrow through the end of the race, with no precipitation expected.