By: Stephen McCoy
For Friday, a high pressure upper level ridge will be stretched through much of the southern US, with its edge approaching the Midwest; an accompanying surface high pressure system will be present underneath the ridge. A surface low pressure system will also be present to the west/northwest of the region in the northern plains. The combination of the cyclonic rotation around the low and the anti-cyclonic rotation around the high will result in surface winds over central Iowa from the south/southeast. The winds will help transport high levels of moisture to the region overnight Thursday into Friday morning. With similar air and dew point temperatures in the morning under a temperature inversion, fog may be possible near sunrise. Both air and dew point temperatures will increase through the day, with air temperatures reaching the upper 80's F and dew point temperatures reaching the mid 70's F. As a result of the warmer dew point temperatures, heat index values or "feels like" temperatures are expected to reach the upper 90's F. Race-time temperatures will be closer to the low 80's, though with consistent dew point temperatures, heat index values will still be in the low to mid 90's; temperatures will decrease throughout the evening. Partly to mostly cloudy skies will be present through much of the day.
A slight chance for isolated to scattered showers is also present for Friday afternoon due to the large influx of moisture over the region. Current forecast model output suggests thunderstorms in the region during the afternoon time period, though there is uncertainty on the specifics of when/where individual storms will be. Current impacts for track activities is low, however a passing storm would likely delay or possibly cancel qualifying.
During Saturday, the aforementioned surface low pressure system is expected to move eastward across the Great Lakes region, with a cold front trailing to the southwest of the center. Throughout Saturday, the front will remain to the northwest of Iowa, resulting in surface winds continuing from the south. Warmer temperatures are then expected for Saturday, with a low in the mid 70's and a high in the low 90's. Dew point temperatures in the mid to upper 70's will cause heat index values to approach triple digits in the afternoon, and could last into the evening, including the start of Saturday's race. Adding insult to injury, little cloud cover is anticipated during the day, meaning that health risks such as sunstroke, heat cramps, and heat exhaustion are a possibility.
A slight chance for isolated to scattered showers is also present for Friday afternoon due to the large influx of moisture over the region. Current forecast model output suggests thunderstorms in the region during the afternoon time period, though there is uncertainty on the specifics of when/where individual storms will be. Current impacts for track activities is low, however a passing storm would likely delay or possibly cancel qualifying.
During Saturday, the aforementioned surface low pressure system is expected to move eastward across the Great Lakes region, with a cold front trailing to the southwest of the center. Throughout Saturday, the front will remain to the northwest of Iowa, resulting in surface winds continuing from the south. Warmer temperatures are then expected for Saturday, with a low in the mid 70's and a high in the low 90's. Dew point temperatures in the mid to upper 70's will cause heat index values to approach triple digits in the afternoon, and could last into the evening, including the start of Saturday's race. Adding insult to injury, little cloud cover is anticipated during the day, meaning that health risks such as sunstroke, heat cramps, and heat exhaustion are a possibility.
