A cold front is still on track to cross northern Florida on Thursday. The good news is that moisture with the front appears limited, so I expect that shower coverage around the area will be isolated to scattered at best. If there is any rain at the track, it will be light - just a few hundredths of an inch. This is why I have a green flag for my weather impact scale. The timing of any potential showers appears to be in the afternoon, during IWSC and CTSC qualifying. But again, it should be too light to really have much impact on the action. Winds on Thursday will be borderline breezy, at 10 to 15 mph from the southwest.
Friday will have a noticeable drop in temperatures behind the cold front. With a mix of clouds and sun, highs will reach the mid 60s. There may be a little more cloud cover moving in on Saturday, and highs will continue to be cool for Daytona, in the lower 60s (normal highs are around 70 degrees).
An upper level low pressure disturbance is expected to move across the Gulf of Mexico on Sunday. This will likely bring overcast high clouds to the track for the final hours of the race, and possibly some light sprinkles before it ends. The end of the race is at 2:30 pm, and it will be close as to whether there is measurable rainfall before that time. One difficultly is that much of the moisture in the atmosphere will be in the mid to upper levels, while the lower levels will remain dry on Sunday morning. Rain falling into drier air tends to evaporate before it reaches the ground, but forecasting such small details this far out is very uncertain.
This image shows a vertical profile of moisture and lift at Daytona, and how they change with time. The vertical scale is height in the atmosphere, and the horizontal scale is time. Time starts on the right, starting today, and moving toward the left is later in time, ending on Monday. The image is relative humidity, with greater moisture shown in blue shades and drier and in brown to yellow shades. Yellow solid lines are when air is rising. I have indicated the time period of the race with the white lines and arrows.
The bottom line, as of today, is that some sprinkles will be possible before the race ends, but measurable rainfall should hold off until after the end. If the current timing shifts a little earlier, then there could be a greater chance of measurable rain during the race.