By: Stephen McCoy

Overnight Thursday, a mid-level jet streak is expected to influence the development of a surface low pressure system on the eastern side of the Rockies. During the morning on Friday, falling pressure along an already-present cold front over the northern plains will allow a second system to spawn from the initial surface low. This second low will track eastward into the Midwest with a cold front bridging the two systems and extending into the southern Plains. A stalled stationary front over central Texas will bring winds from the south to the region, resulting in near average temperatures for Friday. A chance for fog and/or mist is possible for the morning as dew point temperatures will be close to the air temperature. Mostly cloudy to full overcast conditions are likely through the day and for much of the weekend as low level winds bring moisture from the south to southeast.

Saturday's conditions will be similar to Friday's as winds continue from the south to southeast, though they are expected to increase as the cold front approaches the region; a chance of fog is possible again for Saturday morning.

The timing of the cold front passage is still being disputed among the models, though the model average points more towards overnight Saturday or Sunday morning; a chance for scattered showers exists ahead of the front. Once the front passes, precipitation chances will decrease but temperatures will also decrease due to strong northerly winds transporting cooler air to the region, which is why the afternoon temperature is colder than the morning temperature. However, timing is again important as a later frontal passage will allow temperatures to increase during the day before dropping behind the front. The models are showing both scenarios, with a 30+ °F spread for the high temperature on Sunday. Regardless of timing, conditions will likely be overcast ahead of the front before clearing as it passes through the region.

By: Stephen McCoy

According to the GFS, a mid to upper level jet streak will move over Colorado on Friday, leading to the development of a surface low pressure system on the eastern side of the Rockies. The initial position of the system near the New Mexico/Oklahoma/Texas border will result in mostly normal temperatures on Friday as winds transport warm air in from the south. For the most part, the models agree up to this point.

Overnight Friday, the GFS suggests a cold front to form from the low pressure system, which could track quickly into the southeast with help from the mid-level jet. The cold front is shown to set up in an east-west orientation over the southern Plains and pushing southward into the morning and mid-day on Saturday. The front could bring some small (less than 0.1 inch) amounts of precipitation during the morning due to approaching colder air undercutting the warmer air from Friday. Conditions during the day on Saturday could be windy with some stronger gusts possible.

However, the Euro model suggests the cold front won't approach the region until mid-day Saturday, which will allow temperatures to warm through the morning. The approaching front, coupled with southerly low-level winds, is expected (by the Euro) to cause nearly an inch of precipitation through the afternoon and evening. At the moment, the Euro run is an outlier among the model spread, though I wanted to include it in case the models trended towards this result. This uncertainty in the frontal passage timing isn't lost on the other models though as currently there is a 15°F spread for the high temperature on Saturday. Due to this spread, I'm expecting multiple elements of the forecast to change in the next update.

There is more of a consensus among the models for Sunday, indicating conditions will likely be overcast with a slight chance of precipitation due to southwesterly .low-level winds bringing moisture to central Texas from the Gulf. However, much like Saturday, there is a large spread in the temperatures for the day and I expect the values to change between now and the next update.

By: Stephen McCoy

For the past three races of the Rolex 24 hours of Daytona, there’s been periods of rain that have been bothersome to teams, drivers, track officials, and fans. But the rain seen at the 2019 iteration stands out from the previous two years. A veritable deluge of precipitation began in the 4:00-5:00 hour on Sunday and refused to let up, causing IMSA to call the race ten minutes before the conclusion of 24 hours after two red flag periods with multiple full course yellows in between. The question though is why all the rain? What made this year’s weather conditions so different than those seen recently?

To begin, I’ll look at the atmosphere on Saturday night.

By Doug Schneider

The chance of a shower or thunderstorm occurring in the Bathurst area Saturday afternoon looks a little bit higher with the latest model runs. It is still a fairly low chance, just 30%, and if it does occur, I don't expect that it will have a big impact on the racing. Any showers in the area should produce just light and brief rainfall. The chance of lightning in the area is even lower, maybe around 10%, but it can't be ruled out entirely. The timing of any potential showers appears to be around or after 4 pm local time, which may affect the Combined Sedans race and the Top 10 Shootout.

Radar coverage is rather sparse for inland parts of New South Wales, but here's a link to a radar near Sydney.

The weather for the race continues to look dry and warmer, with temperatures at start time in the mid/upper teens C or lower 60s F. With a good amount of sunshine expected, high temperatures will reach the lower 30s C or upper 80s F by the end of the race.