By: Stephen McCoy

Slightly below-average temperatures are in the forecast for the 24 Hours of COTA, with sunny and breezy conditions on Friday giving way to more cloudy and windier conditions on Saturday and Sunday. Timing of  a cold front passage on Sunday could determine if temperatures remain in the 60's F or drop to the lower 50's F for the day.

A strong upper level shortwave trough will move through the region towards the southeast US through the beginning of the week into Thursday. A surface low pressure system is expected to develop over the Gulf Coast ahead of the trough, moving northeast up the Atlantic coast late Thursday; an area of high pressure will build at the surface as the low move out of the region. Behind the upper level trough, conditions will return to zonal flow, with winds coming from due west through the end of the week.

Sunny conditions are expected on Friday with dry air moving in to the region at all levels of the atmosphere. Initial surface winds from the southwest will contribute to a low temperature in the mid 40's F, however as the day progresses, winds will shift towards the south as the surface high pressure system slowly tracks eastward across Louisiana and Mississippi. The winds will bring warmer air from the Gulf to central Texas, resulting in high temperatures in the mid 60's F.

Similar conditions are expected on Saturday, with the exception of clear skies, as the zonal flow in the upper levels will bring moisture originating over the Pacific into the area. Conditions will likely start clear in the morning, but cloud cover will increase through the day as the upper level moisture moves over around mid-day. Surface winds will shift slightly during the day to the southeast, causing temperatures to be slightly warmer in the upper 60's F.

Going back to Wednesday, a surface low pressure system will develop over Canada (known as an "Alberta Clipper") and track eastwards through the week. After approaching the Great Lakes region on Saturday, a cold front will extend from the system well to the southwest, reaching into Oklahoma and northern Texas. As the low continues its track, the cold front will track southward, approaching central Texas by Sunday morning. There is currently a split in the models as to when the front will reach the region, with the ECMWF indicating a passage in the early morning before sunrise and the GFS indicating a passage closer to mid-day.

This graphic follows the synoptic pattern provided by the GFS where southeasterly winds from Saturday continue to bring warmer temperatures into Sunday morning before the frontal passage. The result would be a low temperature about 10 degrees warmer than Friday and Saturday. The high temperature would only be a few degrees warmer than the low as the front would only allow daytime heating to occur for a couple of hours before it passes and drops temperatures into the lower 50's F. If the Euro is correct, temperatures will be cooler than on this graphic with the high temperature occurring just after sunrise before dropping to the lower 50's F for the remainder of the day. Regardless of timing of the frontal passage, winds will shift to the north, with wind speeds around 10-15 mph and gusts approaching 25 mph. The front will also bring overcast conditions to the region for most of the day.

By Doug Schneider

The weather pattern across eastern China this weekend will be a wet one that will not change much from one day to the next, which means that rain will be a factor in the racing each day.

A front is expected to stall near the Shanghai area on Thursday. Moist air spreading from south to north will run up and over this front. A steady rain will start on Thursday night and continue through Friday. The upper level flow will be from west to east, parallel to the front, so the front will not move much over the weekend. It may drift slightly south, but that should have little impact on the weather, as rain will likely continue into Saturday, and probably into Sunday. One positive aspect of this forecast is that the rain does not appear to be heavy. I expect it will be a steady, persistent light rain that will produce about a quarter to half an inch  (6 to 13 mm) each day. As a result, I have a Low impact each day, meaning that rain tires will be needed and there may be some delays to the action, but I do not expect the rain to be heavy enough to cause cancellations. 

That's how the forecast looks today, and I plan to have the next update posted on Wednesday, unless there is a big change in the models before then.

By: Stephen McCoy

Conditions remain mostly the same for Saturday and Sunday at Sebring. Widespread fog is possible in the morning on Saturday though conditions will clear before mid-day. Partly cloudy skies are expected for the earlier portions of the day before transitioning to mostly cloudy skies as the cold front passes over. On Sunday, a slight chance for scattered afternoon showers is re-introduced as northeasterly winds are expected to bring moisture from the Atlantic to the region which will contribute to the chance for precipitation. However, chances are only at 20% due to output from the simulated reflectivity parameter of the NAM 3km model showing mostly scattered showers in the area with little to no rain occurring at the track.

By: Stephen McCoy

Temperatures in this update remain mostly consistent with the initial forecast, with high temperatures in the low to mid 80's each day. Dew point temperatures in the mid to upper 60's will cause heat index values in the upper 80's on Friday, and the mid 80's on Saturday and Sunday. The long-range models have shifted the chances for precipitation to Friday as moisture propagates over the region in the lower levels. However, due to the short-term models not showing any occurrence of rain through the weekend chances are only slight and if showers do occur, they will be mostly scattered.

A cold front is still likely to move southeast through Florida on Saturday, however instead of  transitioning to a stationary front, it is expected to continue moving through south Florida into Sunday. Surface winds on Saturday will be mostly from the north with the approach of the front, with upper level winds from the west to southwest bringing mostly cloudy conditions to the region in the late afternoon to evening on Saturday. On Sunday, winds are expected out of the northeast as a surface high pressure system builds in over the southeast region. The winds will bring moisture off the Atlantic, resulting in partly to mostly cloudy conditions primarily concentrated in the lower levels of the atmosphere.

By: Stephen McCoy

Hot and muggy conditions await for the Michelin IMSA SportsCar Encore at Sebring this weekend with temperatures in the mid 80's expected each day. Partly cloudy with chances for precipitation are in the forecast for Saturday and Sunday after sunny conditions for Friday.

Zonal flow in the mid and upper levels of the atmosphere will be present through the day on Friday, bringing dry air from the west to the region. Some light cloud cover could be possible during the day as some moisture moves in from southeasterly winds in the lower levels. Surface winds also from the southeast will bring warm, moist air to the region, causing temperatures to reach the mid-80's with dew point temperatures in the upper 60's; subsequently, heat index values are likely to reach 90F.

Overnight Friday into Saturday, a surface low pressure system is expected to develop off the mid-Atlantic coast ahead of a strong upper level shortwave trough; a cold front will extend from this system to the southwest into the Gulf of Mexico. The surface low is expected to move to the northeast up the east coast of the US through Saturday, while the cold front is expected to slowly move to the southeast. The front will likely reach Sebring in the mid-afternoon to evening, though due to it stretching from New England to the Gulf Coast, it will significantly weaken through the day. The weakened front is unlikely to affect the temperature for the day, however it is expected to provide enough lift to cause a slight chance for scattered showers or thunderstorms as it approaches the track. As the front passes, surface winds will shift to the north to northeast as high pressure builds into the southeast region.

Similar conditions are expected on Sunday as the cold front transition into a stationary front over central Florida. Surface winds will continue from the north and northeast, though wind speeds are expected to strengthen as the winds come off the Atlantic as opposed to over land. The stationary front will bring a chance for showers or thunderstorms to the region, especially in the afternoon and could have an impact on Sunday's race. Lingering moisture in the lower levels of the atmosphere will cause some partly to mostly cloudy conditions during the day, with cloud cover increasing in the evening.