BOISE, Idaho — Mother Nature may have gotten too stuck on the Thanksgiving theme, giving us extra helpings of the same weather pattern for about the next week or so. A strengthening inversion will lead to an increasing haze in valley areas as well as chances for persistent fog and frosty mornings. While the inversion conditions are in place, it won't hurt to give yourself an extra 5 minutes or so in your morning routine to account for a frosty windshield or slower drive time due to the fog.
We've seen some of the dense fog at the end of this holiday weekend in the Treasure Valley. Some places like Ontario saw visibility drop down to 0 miles. In clear conditions, visibility is 10 miles. Due to the fog, there's a Dense Fog Advisory in place until Monday morning at 11 am for cities like Nampa, Caldwell, Nyssa, and Ontario where driving may be difficult at times because of the low visibility. Fog is possible in other valley spots throughout the next week as well.
The inversion is spurred by a high pressure ridge that will keep a lid on the valley, trapping cold air and pollution closer to the surface. Temperatures will be almost exactly the same for the next 7 days, with very slight warming ahead. Monday's valley high temps will be in the lower 40's and by Friday closer to the mid 40's while morning temps stay closer to the 20's.
An Air Stagnation Advisory is still in effect until Friday at 9pm. This is also due to the inversion that is near the surface trapping pollutants in valley areas. We are expecting an extended period of stagnant air with light winds and little atmospheric mixing. Portions of South Central, Southwest, and West Central Idaho as well as Northeast and Southeast Oregon are within the advised area. This is important to note for sensitive groups as air quality may be lowered with pollutants remaining stagnant in the air.
Mountains will see several degrees of warming each day while the inversion keeps valley temperatures mostly unchanged. The high-pressure system will continue to dominate. While there's a chance of a weak system bringing some snow and rain precipitation on Saturday, there is low confidence in the possible weak system at this point. There is a possibility that the inversion scours out on Sunday, but uncertainty remains.
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KTVB Weather Team
- Chief Meteorologist Rachel Garceau joined KTVB’s First Alert Weather team in early 2023 and was promoted to Chief Meteorologist in September of 2024. While Rachel started her news career behind the scenes as a producer, she eventually moved in front of the camera as a news anchor and fill-in weather anchor. After spending some time on the green screen, Rachel realized she had a passion for the “why” behind the weather, and especially for the challenges presented by forecasting Idaho’s four distinct seasons. You can catch Rachel's forecasts Sunday through Thursday evenings at 5, 6 and 10pm.
- Meteorologist Sophia Bliss has been a part of the KTVB team since December of 2019. She started producing for the Wake Up Idaho team and continues to work as a producer. Additionally, Sophia is a meteorologist. She writes special weather stories and forecasts as a member of the First Alert Weather team. She loves the science of weather and enjoys the opportunity to explain how “magic” of the science works.
- Weather Anchor Hector Mendoza joined KTVB in June of 2023 as a Multi Skilled Journalist and became a member of the First Alert Weather team shortly thereafter, in July of 2023. Hector started off as the weather anchor for KTVB's Saturday Morning News but rang in 2024 by also taking over weather duties for the News at Noon. Whether planning for the week ahead or just wondering what's in store for the weekend, Hector is excited to help keep Idahoans informed about the conditions that matter most to them. You can catch him on Saturday mornings from 8-10 a.m. and on the News at Noon Tuesday through Friday.
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