by Scott Martin.

Sorry for the late post as I have been dealing with computer issues and other issues. No rain and cool temperatures can be expected out at the Indianapolis Motor Speedway, along with a good breezy at times and plenty of sunshine. I'll have a more in-depth forecast update later tonight.

By Doug Schneider

It turns out that the weather will be beautiful for Petit Le Mans, and the remains of Ian will have no impact. See the graphics below for the details.

I am sorry for the bad forecasts I made earlier this week. In my first forecast discussion, I mentioned two possible scenarios with Ian, one that kept it close to the Atlantic Coast, and one that brought it inland across Georgia. I went with the second scenario, and I was wrong. Ian crossed Florida, went back over the ocean, then tracked into the Carolinas. So my bad forecast was good news for everyone at Road Atlanta, and I'm very glad that everyone can enjoy the race with excellent weather. I just have to watch it with some egg on my face. 

By Doug Schneider

​Click images to enlarge

The forecast looks much better for Petit Le Mans today. The forecast track of Ian has shifted to the east, which will mean less of an impact on Road Atlanta. Another positive aspect of this forecast update is that most of the rain will fall on Friday night, with less impacts during the scheduled on-track times.

Here's the NWS forecast rainfall along the path of Ian through Sunday morning:

Road Atlanta is on the edge of the white and light green area. I expect that 1 inch of rain could be a high end amount, but the most likely rain amount will be around a half inch. This is much less than expected a few days ago when Ian was forecast to track directly across Georgia. 

Rain showers are expected to move into the area Friday afternoon, and increase in frequency through the evening. The WeatherTech qualifying session has the potential to have a shower, but I expect it to be light enough to allow the session to be held. Friday night won't be great for campers as rain picks up. Showers will continue to be on and off through Saturday morning, which could impact the morning warm up session. But the frequency and intensity of showers will be falling through the day, and I think all 10 hours of the race can be held without major disruption.

With the track of Ian being farther to the east, wind will not be as much of an impact. It will be breezy every day, with sustained winds of 15 to 25 mph, gusting between 30 and 35 mph at times. Objects will need to be secured to keep them from blowing around, but I don't think this should be a safety issue for campers. 

By Doug Schneider

Key Messages and Impacts:

1) The remnants of Hurricane Ian will track across eastern Georgia on Saturday. Windy conditions will develop on Friday night and continue through Saturday. Sustained winds during this time are expected to be between 15 and 30 mph, with gusts of 40 to 45 mph. Possible impacts from the winds may be tree branches and/or weak trees blown down. This is a potential hazard for campers to be aware of and prepare for. Being in a tent on Friday night under trees may be hazardous; campers should consider finding sturdy shelter.
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2) Rain is expected to spread into the area on Friday evening, with heavy rain at times from Friday night through Saturday. Between 2 and 4 inches is expected during that period, which may lead to flooding of low lying areas and small creeks and streams. There is a creek that runs behind the outer paddock area, past turn 1, and near the corner marshals' camping area. Camping near this creek should be avoided. 

​Forecast Discussion:

The main change to the forecast today is to push the timing of rain from the remnants of Ian later into Friday night and Saturday, to account for the slower forecast speed of Ian (click images to enlarge). 

The National Hurricane Center forecast as of 8 AM this morning is below. For the latest forecast from the NHC, click here.

The forecast has shifted to the east, which is somewhat good news for impacts at Road Atlanta. This track takes the storm inland sooner than if it made landfall father west along the Florida Panhandle. This extra time over land will cause the storm to weaker more before its effects are felt in northern Georgia. Still, it will be getting quite windy starting Friday night and continuing through Saturday. Gusts of 40 to 45 mph are expected, which may be strong enough to blow down some weak trees or tree branches.

​Below is the forecast rainfall graphic from the NWS Weather Prediction Center:

At Road Atlanta, between 2 and 4 inches of rain is forecast. Most of this is expected to fall from Friday night through Saturday afternoon. Avoid camping in low lying areas and near creeks, which will have a better chance of flooding. 

In terms of how the racing will be affected, it will be a question of when a heavy shower passes over the track, and whether the rain can run off the racing surface quickly enough to avoid ponding. I think it is likely that there will be some red flag periods during Saturday's race. It is possible that the rain could ease up enough late in the day on Saturday to allow for improving conditions for racing. But it's still early to pin that down with any confidence. 

Check back for updates, and be sure to follow @RacecastWx on Twitter, and RacecastWeather on Facebook and Instagram.

By Doug Schneider

Click on images below to enlarge

It's going to be a challenging week to forecast for Petit Le Mans. What is now Tropical Storm Ian in the Caribbean Sea is expected to track north and become a major hurricane as it moves into the Gulf of Mexico. Below is the forecast from the National Hurricane Center as of 5 pm EDT Sunday.

To better understand what the forecast cone means, here's a good graphic. 

The current NHC forecast track has the potential to produce significant impacts at Road Atlanta on Friday, Friday night, and Saturday. There are a couple scenarios that will affect how much impact Ian will have on the racing.

Scenario 1 - Ian takes a track toward the eastern edge of the forecast cone, and makes landfall in the Florida Peninsula, somewhere near Tampa, and tracks northeast, staying offshore of the Georgia coast. In this scenario, I expect minimal impacts to Road Atlanta. If this happens, there may be some showers and breezy conditions on Friday, but I think the racing would be able to be held on schedule.

Scenario 2 - Ian takes a track that is in the middle or on the western side of the forecast cone, making landfall along the Florida Panhandle, and into Georgia. If this happens, there may be significant wind and rainfall at Road Atlanta on Friday into Saturday. This could cause major disruptions to the racing schedule, as well as pose a possible threat of downed trees and flooding. This could be a safety hazard to people who are camping. 

As of today, I think Scenario 2 is the most likely one to happen. I don't know what IMSA can do to delay the event or reschedule, but the current forecast track and timing of Ian does not look good for holding a race with a track full of people in tents and campers. 

I've seen some comparisons on Twitter between this year and to the 2015 race. This weather pattern is nothing like what happened in 2015. That year, Hurricane Joaquin was well off the Atlantic coast, near the Bahamas, and a low pressure trough over the central U.S. was drawing moisture from Joaquin to the northwest. There was a band of tropical moisture that produced heavy rain over Road Atlanta, but it was not directly associated with Joaquin. There was also no impact from wind.
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This situation is very different. This is expected to be a major hurricane that makes landfall on the Florida coast, and tracks directly into Georgia. The impacts from this system could be much more significant than 2015, especially in regard to wind. 

It is still early to say that any of this will happen with a high level of confidence, but the potential exists. I will have another post up here on Tuesday at the latest, but I will be posting on the @RacecastWx Twitter account every day with the latest forecast track and possible impacts on the event. 

By Doug Schneider

All eyes on are what will happen with Hurricane Kay and how it might impact the INDYCAR season finale at WeatherTech Raceway Laguna Seca. 

Hurricane Kay is forecast to track up the northwest coast of Mexico today and Friday, and weaken to a tropical storm. By Saturday night, it will be off the coast of San Diego, and start to curve toward the west. While the remnants of Kay won't have a direct impact on Monterey, it will have the effect of spreading moisture into the area. Whether there will be enough moisture to produce some rain at the track is uncertain, but it is at least a possibility, so I've added a small chance of rain to Sunday's forecast. I am confident that moisture from Kay will increase cloud cover on Saturday and Sunday, which will make for pleasant temperatures with highs in the mid 70s. 

By Doug Schneider

Hard to believe the INDYCAR season finale is already here. It's been a great season, and the finale should be very exciting with multiple drivers in contention for the championship. The weather should cooperate and not impact the race, but there are some uncertainties to the forecast that aren't shown in the graphic.

A large high pressure system will cover the western U.S. on Friday, and provide a sunny and warm day at the track. Meanwhile, Hurricane Kay will be tracking northward off the west coast of the Baja Peninsula. Below is the National Hurricane Center's forecast for Kay through Saturday. 

As you can see in the graphic, Kay is expected to take a northwesterly turn on Saturday, and it will likely stay well south and west of Monterey through Sunday. The main effect of Kay will be to increase clouds on Saturday and Sunday. I have seen some forecasts that have a chance of showers in the Monterey area on Sunday, based on Kay taking a track that stays closer to the California coast and spreading some moisture into the area. But I think it is more likely that the large high pressure ridge over the western U.S. will steer Kay away from the coast. So I can't completely rule out a shower on Sunday, but I think the chance is very low at this time. I'll have another update posted later this week before the event begins. 

By: Stephen McCoy

The weather pattern for this week over Portland is expected to be fairly stable, but with the possibility of a cold front approaching the region on Saturday. Dry conditions and minimal cloud cover will be present as a result. Some light fog may be possible during the early mornings, but will quickly clear as temperatures increase from morning lows in the 60's to highs in the 80s; temperatures may be slightly cooler on Saturday depending on the location of the front. The front may also bring a slight chance for isolated showers to the region Saturday morning, but will cause little to no impact to the track. Relatively light winds are expected throughout the weekend, shifting from the South/Southwest on Friday to the North/Northwest for Saturday and Sunday.