By: Stephen McCoy
Conditions remain relatively consistent for the rest of the weekend at Sonoma Raceay. Saturday's forecast stays mostly unchanged other than the possibility of some increased cloud cover in the upper levels during the afternoon. For Sunday, recent model runs have been trending warmer with a high temperature near 90°, possibly as a combination of less cloud cover during the morning and northerly surface winds during the day. Previous model runs were indicating winds from the west to southwest, which would have brought air to the region from the Pacific. Winds from the north will move over land, which warms much quicker and to higher temperatures than the water. Dew point temperatures in the mid 40's will likely keep conditions feeling cooler than actual air temperatures.
By: Stephen McCoy
Weather conditions for Sonoma Raceway are mostly consistent in this forecast update with the initial forecast from Monday. Friday morning, the upper level trough mentioned in the previous forecast will still be centered over the region with winds at these levels from the direct west. Moisture will be brought in to the region from the Pacific, resulting in partly to mostly cloudy conditions in the upper levels during the morning. Conditions are expected to clear during the afternoon as upper level winds shift to the northwest.
Warmer temperatures are likely for Saturday as surface and low levels winds will be from the north to northeast, transporting warmer air to the region as they move over the land. Much like in the previous forecast, upper level winds will be from the southwest on Sunday and will cause some cloudier conditions over the track. Recent model runs show increased moisture being moved into area, which will increase cloud cover as a result.
By: Stephen McCoy
Typical late-spring California weather awaits for this weekend at Sonoma Raceway. After a few days in the mid-80's to start the week, temperatures will cool to the 70's before a low 80 degree Sunday. Full sun to partly cloudy conditions are likely with no precipitation expected.
An upper level trough is expected to move through the Pacific Northwest during the day on Friday, with the southern tip of the trough moving over the Bay Area early Friday morning. Upper level winds behind the axis of the trough will be from the northwest bringing cooler, drier air to the region. Winds in the low-to-mid levels will follow this pattern, with the result being clear conditions throughout the day. An area of high pressure at the surface will build in over the Pacific as an upper level ridge moves in behind the trough. The high is expected to bring temperatures around 10-15 °F cooler than temperatures earlier in the week, beginning Thursday as winds shift to the northwest.
Similar conditions are expected for Saturday, though temperatures will be slightly warmer due to winds from the north to northwest moving over land instead of the cooler ocean waters; surface wind speeds will also be slightly lower due to this reason. In the upper levels, winds are expected from the west to southwest as a ridge moves into the Baja California region. These winds will help transport moisture from the tropics, resulting in some light upper level cloud cover during the day. Upper level winds continuing from the southwest will cause partly cloudy conditions over the region, while surface winds from the west to southwest will result in the warmest temperatures of the weekend on Sunday.
By Doug Schneider
I wanted to get a quick update on the weather situation this morning and what can be expected at Belle Isle Park this afternoon. It appears likely that there will be weather impacts during the racing this afternoon, especially the IndyCar race.
Here's what's happening this morning on radar across the Great Lakes:
Low pressure is located over Wisconsin, with a stationary from stretching east across central Michigan. Showers are tracking E-SE along this front. For the morning hours, the shower and thunderstorm activity will stay to the north of Detroit, near the front.
Through the day, the low pressure area will track along the front, and the front will start to drift to the south. This will start to bring the showers and storms closer to Belle Isle in the afternoon. In addition, there will be a good amount of instability developing with daytime heating - it will be partly to mostly sunny for much of the morning and early afternoon. This instability will result in more showers and thunderstorms developing near the front the low pressure center, and some of these storms could become strong.
Here is one model's (HRRR) depiction of what the radar will look like and where the low pressure center will be at 5 pm this afternoon:
Here's what I'm expecting at Belle Isle today - there may be a light and brief passing shower at any time during the day, but the chance of one is very low - maybe 20% or less. Then after 3 pm, the chance of showers and thunderstorms will start to rise (about 60%), with storms most likely to arrive sometime between 4 pm and 6 pm. The storms are expected to produce frequent lightning and heavy downpours. They may also be capable of producing gusty winds and hail.
With the IndyCar race being run from 3:40 to 5:45 pm, it is likely that the race will be impacted. The extent of the impact will depend on how much rain falls, which can be highly variable depending on whether a storm tracks directly over the track or just skirts by. I do think that there will be lightning in the area, which will require a stoppage of the race.
If you are going to Belle Isle today, stay aware of any storms that are approaching and take action when any calls to find shelter are announced. Have a plan ahead of time to get to a sturdy shelter.
By Doug Schneider
The forecast graphic for the Detroit Grand Prix hasn't changed much from Wednesday, but there are some details on the timing of rain chances on Saturday that are coming into better focus today. More details on that below.
Today continues to look like a beautiful day at Belle Isle Park. There will be abundant sunshine and warm temperatures in the mid 70s. Admission is free today so get out and enjoy some great racing in perfect weather.
A cold front will be approaching Belle Isle from the north on Saturday, which will bring a chance of showers and thunderstorms. There could be showers in the area as early as the pre-sunrise hours of Saturday morning, but if these did occur they would be light and just wet the track a little. Scattered showers will be possible through the morning, but the chance of rain will be rising through the afternoon and evening, as will the threat of thunderstorms. This means that the IndyCar race, which is scheduled from 3:50 pm to 5:45 pm, will have the best chance of rain of Saturday's races. The exact timing of rain is too uncertain to say whether the race will be wet or dry at this time, but I would put the chance of at least part of the race being run in wet conditions at 40%. It is possible that rain could hold off until after the racing ends for the day, and I would put the chance of that happening at 60%.
With thunderstorms being possible on Saturday, fans at the track should stay weather aware, and have a plan to find shelter, preferably in a building, when thunder is heard.
Showers and thunderstorms are likely after sunset Saturday evening as the cold front moves through. High pressure will build in from the north on Sunday, providing cooler temperatures and low humidity. It will be a beautiful day to take in a race, with mostly sunny skies and highs in the mid 60s. It will be a little breezy, with a north wind at 10 to 15 mph.
Doug Schneider, Scott Martin, and Stephen McCoy are race fans and meteorologists dedicated to providing accurate forecasts and timely weather updates at racing venues around the world. We forecast for IndyCar, Indy Lights, Pro Mazda, USF2000, IMSA, Blancpain World Challenge America, and World Endurance Championship, as well as major SCCA and NASA events.