By Doug Schneider

The weather at Road Atlanta late this week will start off hot, but an approaching cold front will bring cooler temperatures through the weekend, but an increasing chance of showers and thunderstorms as well. 

High pressure will be located off the Southeast coast for the middle of this week and into Friday, providing warm temperatures in the lower 90s and mostly sunny skies. There could be an isolated afternoon shower in the north Georgia area, but I expect that these will be mainly in the higher terrain to the north of Road Atlanta, and not affect the track. 

A cold front will be moving southeast across the Tennessee Valley on Friday, and move across northern Georgia on Friday night. The exact position of the front is uncertain this far out, but as of today it is expected to be to the south of Road Atlanta on Saturday. Because of the uncertainty, I will mention a possibility of afternoon showers and thunderstorms, but only a 20% chance. If the front stalls closer to the track, the chance of rain will be higher.

On Sunday the front should start to push back to the north and the flow above the surface turns to the south, which will bring greater moisture into northern Georgia. As a result, the chance of rain will rise, as will the amount of clouds. Scattered showers and thunderstorms are expected, mainly in the afternoon but are possible at any time of the day. As we get closer to the weekend, rain amounts and potential impacts on the racing will come into better focus. For now, I have rated the impact as low.

Check back on Wednesday for the next update.

By: Stephen McCoy

No major changes in the forecast update from Monday. Expect the remnants of now Hurricane Laura to pass to the south of the St. Louis region on its track eastward, bringing a chance for showers and/or thunderstorms around mid-day. In addition, winds are likely to increase as the outer edges of the storm approach; sustained winds are expected around 10-15 mph with gusts upwards of 25 mph. Above normal low temperatures will be present in the morning with seasonal high temperatures in the afternoon.

A cold front following immediately behind the post-tropical system will bring a slight chance for isolated showers and/or thunderstorms during the morning, with precipitation chances diminishing before noon. Winds will shift to the northwest behind the front, though at around the same speeds anticipated for Friday; similar temperatures are also expected. Partly cloudy skies are expected behind the front and will continue into Sunday.

The northwesterly winds on Saturday will cool temperatures overnight, with a low expected in the mid 60's on Sunday morning. A high pressure system passing to the northeast will shift winds to the east to southeast during the day, allowing for temperatures to warm again into the low 80's. The continuing partly cloudy conditions will persist into the afternoon when upper level cloud cover is anticipated to build in.

By: Stephen McCoy

Near-normal conditions are anticipated at Word Wide Technology Raceway this weekend, though conditions on Friday and Saturday will be influenced by the remnants of a tropical system, followed closely behind by a cold front. Chances for precipitation exist for both days, though dry conditions will move in for the remainder of the weekend after noon on Saturday.

For Friday, the remnants of Tropical Storms (potentially Hurricane) Laura is expected to move to the south of the region during the day. Outflow from the system in the upper levels will cause mostly cloudy to overcast conditions starting in the morning and increasing in the afternoon as low level clouds start to build from the approaching post-tropical cyclone. Though the system will move close by the region, sustained wind speeds at the surface are only anticipated around 5-10 mph, however wind gusts could approach 20 mph. The outer edges of Laura will bring a chance for showers and/or thunderstorms to the St. Louis area, with timing potentially delaying a portion of Friday's practice session.

For Saturday and Sunday, as Laura is passing to the south on Friday, an upper level shortwave trough is expected to initiate development of a low pressure system over Minnesota/Wisconsin. Friday night into Saturday, the low is expected to move eastward through the Great Lakes region, with a cold front extending to the southwest. The front will move through the St. Louis region Saturday morning, bringing with it a slight chance for showers and/or thunderstorms. After the front passes, surface winds will increase from the west to northwest as high pressure begins to build in behind the low. Daytime heating will allow the maximum temperature to warm near Friday's high, though temperatures will decrease into the evening and overnight with a low in the mid-60's expected for Sunday. Northwesterly winds aloft will cause clearer conditions to move in Saturday afternoon, continuing through Sunday with the majority of cloud cover in the upper levels. During the day on Sunday, the surface high pressure system will track eastward, causing winds to shift east to southeast, allowing temperatures to warm with a high expected again in the mid 80's.

By: Stephen McCoy

Predicted conditions are still fairly similar for tomorrow's race as they were earlier in the week. Low temperatures will be in the upper 60's tomorrow morning with patchy fog possible in the region as the result of highly saturated air under a low-level temperatures inversion; any fog will dissipate before noon. For the afternoon, air temperatures will be in the low 80's at the green flag, warming to a high in the mid 80's by 5 PM. Winds will likely be out of the south to southwest for the majority of the race at 5-10 mph, with some slightly stronger gusts around 15 mph.

Unfortunately, there is still a slight chance for isolated showers or t-storms in the early part of the afternoon, which could hinder the start of the race. While expected due to an approaching front earlier in the week, recent model runs have shown precipitation as the result of pop-up showers through the region. Exact location of individual storms has varied between models and model runs (and is fairly difficult to predict), however the HRRR has shown a slight increase in number of storms in the surrounding region over the latest iterations. It'll be worth watching overnight to see if the trend continues. Should any changes be necessary from this forecast, an update will be put out tomorrow before the race.

By Doug Schneider

Not much has changed in the foercast for VIR since Monday, with a high chance of rain on Friday tapering off to a lower chance on Saturday, and an even lower chance on Sunday. Timing of the best rain chances has come into better focus, along with potential rain amounts. 

Friday will likely begin with mostly cloudy skies, and possibly a few showers in the area. But through the day, the coverage of showers and thunderstorms will be increasing, making the afternoon the most likely time for storms to have an impact. The hours between 3 pm and 7 pm appear to be the most likely time. With high moisture content in the atmosphere, these storms could produce very heavy downpours. Rain amounts between a quarter and a half inch are expected, although it is possible for a strong storm to drop a half to one inch if it moves directly over the track. Storms may also produce frequent lightning and gusty winds of 30 to 40 mph.

On Saturday, a low pressure system to the west of the Appalachians will continue to trek northeast, so it will have less of an impact on the NC/southern VA region. However, there will still be a southerly flow of moisture into the region, so scattered showers and thunderstorms are expected again in the afternoon. If a storm moves over the track, there could be some wet racing, but these storms should be weaker and shorter-lived than on Friday. A tenth to a quarter inch of rain will be possible.

With the low pressure system moving farther away, Sunday is expected to be mainly a dry day. With afternoon heating, some storms may develop over the mountains to the west, and these may gradually move eastward. I can't completely rule out a shower reaching VIR late in the day, but I think it will be late enough that it won't have an impact on the racing. There will be more sunshine on Sunday, so highs will reach the upper 80s. 

By: Stephen McCoy

Forecasted conditions remain relatively similar from the initial forecast for the Indianapolis 500 from Monday. Slightly cooler temperatures are expected compared to earlier in the week, with partly cloudy conditions for both Carb Day and race day. Precipitation chances have decreased slightly, though there is still the possibility for isolated showers and thunderstorms during Sunday afternoon.

For Friday, an upper level low pressure trough will move into the region Thursday night into Friday morning. Recent runs of forecast models suggest the trough will center itself to the west of central Indiana, contrasting the output from Monday. The trough's position implies an increase in moisture due to southerly winds aloft, resulting in more partly cloudy conditions. At the surface, an area of high pressure over New England will cause light winds from the east to northeast, though wind direction may be variable at times.

For Sunday, a high pressure system located off the Atlantic coast, coupled with a low pressure system passing through southern Quebec will cause a slight increase in winds from the southwest Saturday night into Sunday, leading to warmer low temperatures Sunday morning. The increased air temperatures, in addition to relatively warm dew point temperatures could result in patchy fog in areas near sunrise, though any fog will be gone within the following few hours. An increase in moisture at the mid-to-low levels of the atmosphere could result in some isolated showers through the region during the afternoon, with an approaching cold front possibly provoking the development of thunderstorms.

By Doug Schneider

It pains me to be making a forecast for Michelin GT Challenge weekend at VIR, and not be able to attend. Even though I drive 5 hours to get there, I consider VIR my home track. Mixed weather conditions can be expected for the event, with Friday having the highest chance of rain, Saturday being a lower chance, and Sunday expected to be dry.

To start the period, a deep low pressure trough will be located west of the Appalachian Mountains, with high pressure off the Atlantic coastline. This will provide a southerly flow of moisture deep through the atmosphere, and with a jet streak in the upper levels producing some lift, showers and thunderstorms will be numerous on Friday. They will be possible at any time of the day, but the highest chances will be in the afternoon. I expect that there will be enough rainfall that there will be some delays and stoppages to the day's sessions. 

On Saturday the upper trough moves a little farther east, which should move the main axis of rainfall closer to the coast. There will still be a good amount of moisture in the atmosphere, but not much in the way of lift. So I think that the coverage of showers and storms on Saturday will be more scattered, and occur mainly in the afternoon when heating can provide more instability.

On Sunday the trough will be weakening and moving off to the east, which will result in a more westerly flow that will bring drier air to the region. It will be quite a nice day with partly cloudy to mostly sunny skies, and highs in the upper 80s with slightly lower humidity. 

By: Stephen McCoy

Fairly similar conditions are expected for the Indianapolis 500 this weekend as there were for the practice and qualifying sessions last week. Warm and sunny conditions will be present on Friday, though a cold front approaching the region will bring a chance of showers and thunderstorms on Sunday.

For Friday, an upper level trough will center itself to the east of central Indiana, resulting in upper level winds mostly from the north/northwest through the day. Drier air from Canada will move over the region, causing clear skies for much of the day. At the surface, an area of high pressure will be present over the area, keeping surface winds relatively light from the east to northeast, though at times wind direction will be variable.

For Sunday, an upper level shortwave trough will move through the northern plains on Saturday, allowing a surface low pressure system to form just to the east. The surface low is anticipated to move eastward through southern Quebec with a cold front trailing behind it to the southwest. Sunday morning, the front is expected to approach central Indiana, bringing with it a chance for showers and thunderstorms, along with slightly warmer daytime temperatures and stronger winds. Surface winds will be largely from the southwest ahead of the front, but will shift to the west if the front passes over the region. Partly cloudy skies are expected as a result of the oncoming front along with mid-level moisture moving into the region from the northwest.