By Doug Schneider

The remains of Hurricane Michael have cleared out of Georgia, and it has been a beautiful day at Road Atlanta, although it has been quite windy, with gusts around 30 mph. The Gainsville airport, which is located about 10 miles north of the track, recorded 2.68 inches of rain from Michael.

A cold front has moved through the area, and winds have shifted to the northwest as high pressure builds into the area. This high will continue to dominate the weather pattern over the Southeast through Saturday, which will provide really nice weather for racing Friday and Saturday. Temperatures will be comfortable in the afternoon, reaching the lower to mid 70s, and morning lows will be cool, in the lower 50s. Humidity levels will be very pleasant too. Winds will be lighter tomorrow around 10 mph), and even lighter on Saturday (5-10 mph). 

Since I'll be at the track Friday and Saturday, and since the weather looks quiet, I don't plan to have another post here to update the forecast. I will have some posts on our Twitter and Facebook accounts, which you can find on the right. See you at the track!  

By Doug Schneider

​Click images to enlarge

The forecast for Hurricane Michael has stayed pretty much the same over the past couple days, and so my forecast for Petit Le Mans hasn't changed much either since Sunday.

Scattered light showers have been around northern Georgia today, and that will continue tonight, with showers becoming a little more numerous and heavier Wednesday morning. On/off showers are expected through the day, not directly associated with Michael. These showers should be fairly light, so I've changed the Impact Scale on Wednesday to low. I think the planned testing sessions that day should be able to be run without weather interruptions, although the track will likely be wet at times.

Michael will start to impact the track on Wednesday night. Here's a bullet list of impacts that can be expected from Michael at Road Atlanta:

• Timing - Outer rain bands from Michael will spread into Road Atlanta Wednesday evening, probably around sunset, give or take a few hours. The heaviest rain will fall at the track from after midnight until around noon on Thursday. Rain will be decreasing in intensity and frequency on Thursday afternoon.
• Rain amounts - From Wednesday through Thursday, around 1.5 inches is expected give or take a few tenths, with 2 inches being possible on the high end and around 1 inch possible on the low end. This will likely not be enough rain to cause flooding problems, but there is a creek near the support paddock and the eastern side of the track that will bear watching if amounts are higher than expected.
• Wind - Not expecting wind to be a big problem, but it will be breezy on Wednesday night and Thursday, with sustained winds of 10 to 20 mph and gusts as high as 30 mph at times. This could be an issue for those who are setting up tents or canopies.

A cold front will move through Thursday evening, which will merge with Michael and bring cooler and drier air behind it. A large high pressure system from central Canada will be building southeast, and the weather for Friday and Saturday will be absolutely gorgeous, with a northerly wind bringing highs in the mid 70s and morning lows in the mid 50s.  

By Doug Schneider

'The big story for the weather during Petit Le Mans will be the effects of what is currently Tropical Storm Michael. Michael is currently located just off the Yucatan Penninsula, and is forecast to track north over the next few days. It is expected to make landfall as a Category 1 hurricane along the Florida Panhandle. From there, it is forecast to curve northeast across Georgia and the Carolinas.

So what will be impacts be for Road Atlanta? First, don't focus on the exact track of Michael. The track isn't going make a huge difference in the impacts, because tropical moisture will be spreading across Georgia ahead of it, producing a lot of rain. The intensity rating of Michael won't matter much either, as heavy rain will be the main impact at the track, with wind being a lesser impact. The amount of rain that will fall remains uncertain, but here's what the forecast for the NWS' Weather Prediction Center shows:

That graphic shows 2 to 4 inches of rain at Road Atlanta in northeast Georgia from Wednesday morning through Thursday night. That is certainly possible, but a big factor in the amount of rain at the track will be the speed of Michael. The good news is that the system is expected to keep moving across Georgia and not stall out, as it will get picked up by an upper level trough and cold front approaching from the west. A faster movement will result in less rain. 

The rain from Michael will be around the track from Wednesday through Thursday, but right now it appears that the heaviest rainfall will be Wednesday night, with decreasing rain amounts through Thursday as the system pulls away and a cold front moves through. 

Behind that cold front, high pressure will be building into the Southeast, and the weather looks great for Friday and Saturday. With the departing low of the remnants of Michael and the building high pressure, Friday will be a little breezy. Temperatures and humidity levels will be quite comfortable, with highs in the lower to mid 70s both days, and lows in the 50s. 

By Doug Schneider

Since I'm going to be attending Petit Le Mans, I've been closely watching the models over the past few days. I thought I'd share a general overview of what I'm seeing. Unfortunately, the pattern appears to be shaping up to be a wet one.

The weather pattern for this weekend and early next week across the Southeast will feature a strong high pressure area centered over North Carolina, which will provide warm temperatures and a small (20-30%) chance of showers and thunderstorms each afternoon over north Georgia. This is a typical summer-time pattern for the region, but one that is unusually warm for October. 

​​As we get into the middle part of next week, the high pressure ridge will be shifting eastward off the East Coast, which will produce a flow of moist air from the Gulf of Mexico and Atlantic Ocean into Georgia and the Southern Appalachians. With the high pressure area weakening its grip and greater moisture moving in, the chance of rain will be rising in the Wednesday/Thursday time frame of next week.

The high pressure ridge remains off the East Coast, but a low pressure trough and cold front will begin to track east across the Great Plains late next week. This will strengthen the southerly flow and bring even more moisture into Georgia. A cold front associated with this low pressure system may move into the Southeast states next weekend, which would provide lift and make the chances of rain on race day even higher. 

​Another factor in all this is a tropical system that some the models have been showing in the Gulf of Mexico for the past few days. It's extremely difficult to make any accurate predictions about tropical cyclone formation this far out, but it has been a feature in more than one model for multiple model runs. If there is a tropical cyclone in the northern Gulf late next week, the pattern of a ridge off the East Coast and a trough in the Plains would tend to steer that system northward, into the Southeast states (the GFS model in the above images is one model that does not develop a tropical system - the ECMWF and GFS-FV3 do develop it and track it into the Southeast). 
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So here's what I can say today about the outlook for Petit with a moderate amount of confidence:
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- A good chance of rain each day of the event, with the highest chance of rain on Saturday.
- Mild temperatures and high humidity each day.

Any other details of the forecast, such as rain amounts, have low confidence at this time. And it's WAY too soon to speculate that this will be a repeat of the rain-shortened 2015 Petit Le Mans. The weather pattern this year looks very different than it did that year.

As always, please keep in mind...

​I'll have the full forecast graphic posted here on Sunday. Hopefully by then I can bring some good news for better racing weather than I'm seeing today. I have a feeling this is going to be a tough forecast.

By Doug Schneider

The forecast remains steady for the Monterey Grand Prix at Laguna Seca this weekend, with nice weather still expected. The only potential issue may be fog each morning, which is fairly standard for the Monterey peninsula this time of year.  The fog will burn off between 8 and 10 am, with sunny skies expected for the rest of the day. High temperatures in the low to mid 70s and low humidity will make for very pleasant conditions to take in some great racing action.