By: Stephen McCoy

Conditions look hot and humid for the Michelin GT Challenge at VIR this weekend with chances for precipitation on Friday and Saturday. Heat exhaustion can be a real problem this weekend with heat index values well into the 90's so be sure to take precautionary steps to stay cool and hydrated.

During the week, an upper level shortwave trough will be moving eastward across the country, originating in the Pacific northwest and setting up over the Midwest Thursday into Friday. Ahead of the trough, a surface low pressure system is expected to form over the Great Lakes region and track eastward with the trough. A cold front extending southward from the system will likely affect the track on Friday and/or Saturday. The disparity as to what day the front will pass through is due to the GFS and ECMWF in disagreement. The Euro indicates the frontal passage in the late afternoon or evening on Friday while the GFS shows the front passing Friday night. In both cases, precipitation is expected behind the front and with the front moving through earlier with the Euro, a chance for rain to disrupt on track sessions in the afternoon; precipitation would move through overnight according to the GFS.

With the front passing through, warm winds from the southwest will be expected at the surface, raising air temperatures to the lower 90's in addition to bringing moist air from the south to the region. The increased humidity at the surface will result in heat index values in the mid to upper 90's.

On Saturday, the center of the upper level trough will move through the Mid-Atlantic, continuing to push moisture into the region from the west and southwest. Through much of the region, there will be a slight chance for scattered showers, especially in the afternoon. Where there aren't showers, partly cloudy conditions are expected as moisture persists in the low levels. Surface winds from the west will continues to keep temperatures in the 90's, with dew points in the upper 60's causing heat index values to reach the mid 90's.

For Sunday, the trough will be to the east of the region, tracking into the Atlantic Ocean, resulting in the track being upstream of the center of the trough. Winds in the upper levels will be from the west to northwest bringing drier air to the region. Partly cloudy conditions are expected as the low to mid levels of the atmosphere will have moderate amounts of moisture and with the dry air above, conditions will likely remain the same for the majority of the day. Light winds at the surface from the north and northeast will keep temperatures around 90, though with dew point temperatures in the upper 60's, heat index values will be in the low 90's.

The forecast for this weekend's ABC Supply 500 at Pocono Raceway at this point doesn't look all that bad at this point. Saturday will be a very nice day out at the track with plenty of sun and just a few clouds. Temperatures will be mild, topping out in the mid-70s. Winds will be out of the northwest at 3-7 MPH. Troughing will move into the area late on Saturday and into the day on Sunday and could possibly bring a passing shower to the area on Sunday afternoon, but at this point, those chances look small. Skies will continue to be mostly sunny unless a shower does approach the track, and highs will once again be in the mid-70s.

By Doug Schneider

A low pressure system will move through Silverstone on Thursday, which will make for a wet day for scrutineering. Fortunately, the rest of the event looks like it should be mostly free of rain, with mostly cloudy skies, breezy winds, and comfortable temperatures. 

The low pressure system that brings rain on Thursday will be long gone by Friday, and a weak ridge will build over France and southern England. With a mix of sun and clouds and a westerly wind, temperatures will remain rather cool, with a high near 70 F or low 20s C. Another low pressure system will be tracking between Iceland and Scotland on Saturday, but it should stay far enough north that it will not have much impact on Silverstone. It will be getting breezy with a west wind between 10 and 20 mph with gusts to near 30 mph at times, and the majority of the day will have cloudy conditions. A few drops of rain cannot be ruled out at this time, although it should be so light that I doubt it will have an impact. 

Sunday looks rather like Friday, with a weak ridge building over the area while another low pressure system tracks across the northern Atlantic. With a little more sunshine expected, temperatures will reach the mid 70s F or mid 20s C. Some models are hinting at some light rain on Sunday, so I have a few sprinkles mentioned in the forecast, but like Saturday, I don't expect it will have any impact, if it happens at all.

Other than Sunday, the models are in pretty good agreement on this pattern, so my confidence is moderate right now. There may be some tweaks to the forecast as we get closer to the weekend, so check back through the week for the latest forecast and follow our social media streams on the right..

By: Stephen McCoy

For race day at Utah Motorsports Campus, expect conditions to be much the same as the rest of the weekend. Although air temperatures will be lower than Friday and Saturday, slightly higher dew point temperatures on Sunday will bring the heat index closer to the actual temperature. As I mentioned in my previous forecast, winds in the mid levels will be mostly from the south to southeast, bringing more moisture to the Salt Lake region; this will result in slightly heavier cloud cover on Sunday.

Also in the mid levels is a possibility of hazy conditions through the day. Wildfires to the south and east of the track will continue to burn through the forecast period. With winds from the south to southeast, there is a chance the smoke and haze from these fires could reach the track.

By: Stephen McCoy

Conditions are looking to remain hot in this update for the Grand Prix of Utah at Utah Motorsports Campus. Be sure to stay hydrated as even though low dew point temperatures will be present for the region, heat index values will likely exceed 90 each day.

Not much has changed for the forecast on Friday as an upper level high pressure ridge is still expected to set up over the western United States, creating dry conditions and warming temperatures into the upper 90's. Clear to mostly sunny conditions are likely, though winds from the south in the mid levels could bring a small amount of moisture resulting in some light cloud cover in the afternoon.

Saturday is expected to be warmer than seen in the previous forecast as the upper level high pressure ridge was expected to weaken as it stretched and moved eastward. However in the most recent model runs the ridge instead remains mostly stationary at a constant geopotential height value, creating conditions consistent with those expected for Friday.

On Sunday, more moisture will likely enter the region by ways of southwesterly winds in the mid levels. As a result, expect partly cloudy conditions in the late morning and most of the afternoon. With the upper level high pressure ridge beginning to weaken as it stretches eastward, lower temperatures than the rest of the weekend are likely. However, with slightly higher dew point temperatures on Sunday, heat index values will be closer to the air temperature.