By Doug Schneider

Beautiful California weather can be expected this weekend as IMSA heads to WeatherTech Raceway Laguna Seca. 

A large high pressure ridge will be over the west coast for the second half of this week. Through the weekend, this ridge will shift to the east, and a low pressure trough in the upper levels will approach from the west. The main affect of this will be temperatures that will trend warmer each day of the event, and a slight increase in high clouds on Sunday. 

Morning fog is often an issue at Laguna Seca, and while it can't be ruled out, it is too far out in the forecast to mention it as a problem at this time. Forecasting fog is difficult even a few hours in advance, so I'm not going to try to do it 4 to 6 days in advance. We'll see how that develops in later forecast updates.

By: Stephen McCoy

The general weather pattern of the weekend remains similar to the initial forecast from Monday. High pressure will be present over the region through Thursday before a cold front stretching through much of the east coast move through on Friday. High temperatures ahead of the front will be mostly near-normal in the low to mid 70's; behind the front, Saturday's high temperatures will be in the mid 60's.

Winds on Thursday will start from the east, but will shift towards the south as the day progresses, with mostly cloudy conditions expected in the mid levels during the morning to mid-afternoon, with partly cloudy skies for the later afternoon. A slight chance for isolated showers is possible around mid-day as the front begins its approach; rainfall would likely be in the form of light drizzle. Conditions for Friday will begin as mostly to fully clear before partly to mostly cloudy skies move in during the afternoon. Winds will largely be from the north to northwest during the day; a similar chance for precipitation to Thursday is expected.

The northwesterly winds on Friday will cool temperatures on Saturday to a low in the upper 40's. High pressure building in behind the front will cause winds to shift to the east to northeast, keeping temperatures relatively cool into the day. Zonal upper level flow will cause clear skies for the majority of the day, though some light cloud cover in the low levels may move in during the afternoon to evening.

By: Stephen McCoy

Expect a warm start to the weekend for this weekend's MOTUL Petit Le Mans before a cold front passes through the region on Friday, which will bring a chance for showers ahead of it either Thursday afternoon or overnight into Friday morning. Cooler temperatures are anticipated after the front passes, with only a high in the low 60's for race day.

High pressure will move into the region on Tuesday, remaining present until Friday when a cold front approaches from the west. As a result of the high, and drier air aloft, clear conditions will be present for the day with light winds from the east to northeast. A temperature inversion is expected over the region Wednesday morning, and if dew point temperatures are warm enough, some patchy fog may be possible. Slightly cloudier conditions are anticipated for Thursday as the cold front begins moving through the southeast. Surface winds will once again be light, though from the east to southeast, but increasing and shifting towards the southwest overnight into Friday morning. There is a chance for scattered showers ahead of the front on Thursday, with another light round of isolated showers possible on Friday morning.

The possibility of overnight rain will also bring the possibility of fog Friday morning as the southerly winds ahead of the front cause the surface to become more saturated. After the front passes through, winds will increase from the northwest, with cloud cover gradually decreasing into the afternoon and evening. The cooler air behind the front will result in low temperatures for Saturday in the low 40's and warming to a high around 60 along with clear conditions for much of the day.

By Doug Schneider

The path and timing of Hurricane Delta is coming into better focus today. The good news for Charlotte is that its track has shifted farther to the west. So while rain is still likely at the track this weekend, the impacts of the rain appear lower as the heavier rain is expected to stay to the west, with mainly light on/off showers expected at the Speedway. 

Delta is forecast to make landfall along the Louisiana coast on Friday, then track across Mississippi, Tennessee, and eastern Kentucky through Sunday. The cloud shield on the outer fringes of the hurricane will start to spread over Charlotte on Friday. The morning will start with mostly sunny skies, but high clouds will increase through the day. Rain should hold off until after the evening IMSA practice session. 

Some of the outer rain bands from Delta will start to spread into the area late Friday night or Saturday morning. Through the day, there will be numerous showers around the track, but they will be on and off - it doesn't look like a washout at all. I expect that the majority of this rain will be light, with the total amount of rain expected all day being around one or two tenths of an inch. When I made Monday's forecast I was afraid that heavy rain would be possible, but due to the westward shift of the forecast track, I am much less concerned about that now. This is why I have lowered the Impact rating to low. It will make for some interesting tire strategy during the racing, but it should all be able to be held as scheduled. It will be breezy on Saturday, with a southeast wind at 10-20 mph, gusting up to 30 mph at times.

On Sunday, there will still be showers in the area, mostly in the morning, but they should be scattered and occur less frequently than on Saturday. It is possible that showers could end in time for the Cup race in the afternoon, but I can't say I'm very confident in that yet. An isolated thunderstorm can't be ruled out, but the chance of one at the track is low. 

By Doug Schneider

I'm going to say up front that this is a low confidence forecast, which means that it is likely to have some changes as we get closer to the race weekend. But as of today, it appears that there will be potential for a rather wet event, especially on Saturday. I would love to forecast a dry event as I will be there in person, but I'm afraid it's not looking like the weather will cooperate.

The weather system that will be impacting Charlotte this weekend is now taking shape in the Caribbean Sea, currently Tropical Depression 26, which is forecast to become Tropical Storm Delta. It will be tracking north across the Gulf of Mexico through the week, and is forecast to make landfall as a hurricane on Friday along the Louisiana coast. After it makes landfall, it is expected to curve toward the northeast, and move across Alabama, Georgia, upstate South Carolina, and western North Carolina. The models agree on this general pattern, but the big uncertainty with it is the timing. It appears that rain could arrive as early as Friday evening, potentially during the IMSA practice session that starts at 7:30 pm. Rain showers are likely through Saturday, which will make for some interesting conditions during the Xfinity race and the IMSA race in the evening. It's too early to say how much rain will fall and what the impacts will be, but because it is a system with tropical origins, heavy rain may be possible. It will also be breezy on Saturday, with a southeast wind between 10 and 20 mph, gusting up to 30 mph at times.

The low pressure center is expected to track into Virginia by Sunday morning, and there should be a decreasing chance of rain through the day as it continues a northeast track. But because of uncertainty with timing, I will keep a chance of rain all day on Sunday. There could be showers in the area during the Cup race. 

These tropical systems are often difficult to forecast with high accuracy this far out in the forecast. As a result, my confidence level in this forecast is low, so it will likely change through the week. Be sure to check back for updates through the week.