By Doug Schneider

The forecast for Watkins Glen continues to look very wet this weekend. A low pressure system that has brought a lot of rain to the Southeast over the last few days will continue to track slowly northeast. The counter-clockwise flow around this low will draw a lot of moisture off the Atlantic Ocean into upstate New York, causing periods of showers and thunderstorms at the track on Friday and Saturday. The northeast movement of the low will take it east of the Finger Lakes region on Sunday, which will lower the chance of rain and allow for some partial sunshine, but I expect that afternoon instability will cause scattered showers to develop in the area. 

The uncertainty in this forecast is how much rain will fall. There is a potential for heavy rainfall at times, especially Friday and Saturday. This could cause delays to the on-track activity, as well as localized flooding. Campers should avoid setting up tents in low lying areas which may be prone to flooding. Lightning will also be an issue to stay aware of - make sure you have a place to find shelter when thunder is heard, like inside a car or a building. The National Weather Service Weather Prediction Center forecast rain amounts are around 0.25 to 0.5 inches on Friday, 0.5 to 0.75 inches on Saturday, and 0.1 to 0.25 inches on Sunday. So the range of possible amounts for the event is expected to be between 0.8 and 1.5 inches total. Here's their graphic of rain amounts for Friday through Sunday.

Follow @RacecastWx on Twitter, as I'll try to post regular radar updates through the event. If you're at the track, please tag us in your photos.

By Doug Schneider

A wet weather pattern will be in place across upstate New York this weekend, making for a soggy Sahlen's Six Hours of the Glen.

Thursday will likely have the best weather of the event, with just a small chance of an afternoon shower or thunderstorm. The chance of rain will trend upward, due to a slow-moving low pressure system over the Ohio Valley region that will pump moisture into the Finger Lakes region over the weekend. As the low tracks slowly northeast, showers and thunderstorms will become numerous Friday and Saturday. The highest chance of showers and storms will be in the afternoon hours, but they are possible at any time of the day. I expect that the rain may be heavy at times, along with frequent lightning, which may cause delays and stoppages during some of the on-track sessions.

The low pressure system will be over New England by Sunday, which will cut off the feed of moisture to the area, and lower the chance of showers and storms. Still, there could be enough instability to produce some scattered afternoon activity that could impact the race. With some periods of sunshine between the clouds, temperatures could rise to around 80 degrees. 

Check back later in the week for updates.

By Doug Schneider

Rain will likely be a factor in the 24 Hours of Le Mans, especially around the start of the race on Saturday. 

The weather pattern over western Europe continues to show a low pressure system off the west coast of France, and this will change little over the weekend. This morning, rain showers are occurring along the west coast of France, and through the day, these showers will slowly advance toward the west. Showers are likely in Le Mans by the afternoon. Tonight, the showers are expected to taper off, then return by Saturday morning. Saturday looks like it will be a rather wet day, with periods of rain possible at any time. It does not appear to be a heavy rain, so I expect that the racing will be able to be held as scheduled. But it will make for a challenge for the teams and drivers, especially at the start. Rain amounts on Saturday are expected to be between a quarter and a half inch, or between 6 and 12 mm.

The chance of rain will decrease Saturday night, and I expect that most of Sunday will be dry. However, there is a chance that some showers and thunderstorms will develop in the area during the afternoon. The chance of impacts on the race appear low at this time, but there is some disagreement among the models on where the showers will develop. Hopefully the race can end under good weather conditions, but we will have to keep an eye on the radar.

By Doug Schneider

The pattern across western Europe during the second half of the week will have high pressure over England and the North Sea, with a low pressure system in the eastern Atlantic, off the Iberian Peninsula. As Le Mans practice sessions begin, the weather will be sunny and warm on Wednesday and Thursday, thanks to the high pressure system being dominant. Through the weekend, this pattern will shift slowly east, so that the high loses its grip and the low pressure system spreads moisture into France. Showers are likely to arrive at Le Mans during the afternoon and evening hours on Friday. Showers will continue to be in the area through Saturday. The good news is that this does not look like a very heavy rain. I expect that it will be light enough to allow for the on-track sessions to be held, for the most part. Interruptions should be minimal, but wet tires will likely be needed. On Sunday, there is just a small chance of showers, and I expect that the second half of the race will mostly be dry. 

​Check back later in the week for updates.

By: Stephen McCoy

The updated forecast for Laguna Seca has temperatures a few degrees warmer than the initial forecast with clearer conditions towards the end of the weekend.

The synoptic setup for the latter portion of this week remains similar, however the surface trough mentioned in the previous forecast is now expected to be located a bit further east, approaching the region closer to Sunday. A weaker pressure gradient will result in less cold air advection to the Monterey Bay area. In addition, what was rightfully pointed out, WeatherTech Raceway Laguna Seca is actually a few miles further inland than the city of Monterey so the cooling effect from the bay winds will not be as powerful at the track as directly on the coast. However, even being a few miles away, there is still a possibility for fog during Saturday and Sunday mornings, which will clear into the afternoons; partly cloudy conditions may continue in the low levels.

By: Stephen McCoy

Conditions in Monterey should be fairly similar to those in the previous IMSA race at Long Beach. Temperatures will be in the low-to-mid 60s with partly cloudy skies and some fog possible during the mornings.

On the synoptic scale, a low pressure surface trough is expected to extend along the California coastline, and remain mostly stationary through the weekend. The alignment of the trough will result in surface winds mainly from the northwest throughout much the forecast period; normally we would see a land-sea interaction where winds would flip between the day and night. The moist air off the Pacific Ocean will enter the Monterey Bay area, condensing as it encounters the trough, which will result in partly cloudy conditions in the low-to-mid levels. As the temperatures get cooler in the mornings, this may also lead to some localized areas of fog which have a chance to last into the late morning. 

Temperatures will be near normal for this time of year, though the strength and direction of the surface winds may swing the highs by a few degrees, especially for Saturday and Sunday. For Sunday, cloud cover may be largely in the upper levels due to a cutoff upper level trough located near to the region. We'll see cloudier conditions the further west the trough is, however if the low ends up more to the east, clearer conditions will be more likely.

By: Stephen McCoy

There will be some slightly below-average temperatures for this weekend at Long Beach, however the remaining conditions are to be expected for this time of year in SoCal. We'll see a typical sand-sea interaction each day where winds will move off the land over the Pacific overnight and through the morning before reversing, with afternoon conditions consisting of winds coming onshore. As a result of this interaction, there is a possibility for patchy to widespread fog in the morning after sunrise, but should clear fairly quickly by the late morning and should not last into the afternoon. Skies are expected to start the weekend partly to mostly cloudy in the lower levels of the atmosphere, but should clear out Friday afternoon. Clearer conditions will persist through Saturday, before upper level cloud cover moves in for Sunday.

By Doug Schneider

Click the forecast images to enlarge

Good news with today's forecast update - the cold front that will be approaching Sebring is trending slower, which means a later arrival of showers. A later arrival time closer to sunset means there will be less instability for storms to tap into, so strong storms are unlikely. The coverage of showers is also looking less than it was before, so the chance of shower during the race is lowering.

There are still some timing differences among the models, but I expect that the window for showers and thunderstorms to arrive will be between 7 pm and 10 pm - the last few hours of the race. There is still a potential for a lightning delay, depending on whether a storm tracks close enough to the track, but the risk appears lower than with previous forecasts. The threat of strong wind gusts and heavy rain has also decreased, but again, the threat will depend on whether a storm moves directly over the track. With coverage expected to be scattered, they could miss the track completely. 

I'll try my best to post radar updates during the race on our Twitter account - @RacecastWx.