By Doug Schneider

Not much has changed in the forecast for WeatherTech Raceway Laguna Seca this weekend. No rain is expected through the event, with temperatures starting off warm on Friday but getting cooler each day. The one change to the forecast is to bring in more cloud cover on Sunday, associated with the upper level trough that will be approaching the area. It does not appear that there will be enough moisture for rain, just some partial cloud cover. This trough will also help cool temperatures to the lower to mid 70s on Sunday. It should be a great weekend for racing.

By Doug Schneider

Beautiful California weather is expected this weekend as IMSA visits WeatherTech Raceway Laguna Seca. Sunny skies are expected each day, with pleasant temperatures. There will be a cooling trend each day, with Friday reaching the mid 80s, cooling to highs in the mid 70s on Sunday. This is due to an upper level trough that will be approaching, although it won't have enough moisture to produce rain, or even clouds. 

One thing to watch for as we get closer to the weekend will be morning fog or low clouds. Fog can be pretty common at Laguna Seca if the wind direction and ocean-land temperature difference are right. At this time I think it is unlikely to have any impact, so I'm keeping it out of the forecast.

By: Stephen McCoy

The forecast for Sunday at Watkins Glen has remained mostly consistent with the rest of the week's forecasts. Partly to mostly cloudy conditions will be present through much of the day, varying in height as the air aloft begins to saturate; westerly winds are expected to bring in moisture above the region. South to southeasterly winds at the surface will keep temperatures in the upper 60's to low 70's, but will also allow dew point temperatures to approach 60 °F as moisture moves in from the Atlantic. The saturated atmosphere coupled with minor lifting could result in some scattered showers through the region in the afternoon; a surface trough approaching from the northwest is expected to bring a larger chance for precipitation overnight.

By Doug Schneider

There are no major changes to the forecast for Portland this weekend, as it still looks like the weather will be nice for racing each day. There is a small chance of seeing some light sprinkles in the area on Sunday, but it should not have an impact. 

The main weather feature to affect Portland will be a low pressure system moving slowly across the Pacific toward the Northwest coastline. This will push a front through the Portland area on Saturday night. Most of the rain with this front will stay offshore or just near the coast, and rain will decrease as it moves inland. Still, there may be some sprinkles that reach Portland on Saturday night and Sunday. I don't think there would be enough rain to even measure a hundredth of an inch, if it happens at all. The front will also cause a wind shift from south of Friday and Saturday to west on Sunday. 

By: Stephen McCoy

Some minor changes in this update for Blancpain GT World Challenge America at Watkins Glen, though the general setup remains similar to the initial forecast.

A cold front from a surface low pressure system over Hudson Bay is expected to pass through the region on Friday, bringing a slight chance for isolated showers and/or light rain. West to southwesterly winds ahead of the front will cause near-average temperatures for the day. After the frontal passage, northwesterly winds will cool temperatures to the low-to-mid 50's overnight. With dew point temperatures similar to the air temperatures, there is a possibility of fog in the area Saturday morning; temperatures will rebound to the mid-to-upper 60's. High relative humidity values in the upper and lower levels will result in partly to mostly cloudy conditions through the day.

A surface high pressure system will build into the region on Saturday behind the front, then move off-shore on Sunday. As it leaves the area, a stationary front is expected to setup to the north of the track, causing surface winds to shift to the south to southeast. Westerly winds in the rest of the atmosphere will bring moisture over the region, with much of the air aloft fully saturated. As a result, precipitation chances are higher than in the initial forecast; model guidance suggests the highest chance for showers near or after mid-day.