Heat Wave Forecast to Fry Flathead Valley

Temperatures on Wednesday will hover around 100 degrees in northwest Montana with hot and dry conditions expected to persist through early next week

By Maggie Dresser
Sunset on the Flathead River at Sportsman’s Bridge outside Bigfork on July 31, 2023. Hunter D’Antuono | Flathead Beacon

The National Weather Service has issued a heat advisory in northwest Montana where temperatures are forecast to hover around 100 degrees on Wednesday and stay in the 90s through at least Sunday.

Kalispell is expected to reach 98 degrees on July 10 while Libby could see 105 degrees. Lower valleys in north-central Idaho temperatures could reach 115 degrees.

A strong ridge of high pressure will continue over the Northern Rockies early this week and will persist until at least July 14. A subtle disturbance will pass through the region on Thursday, causing the ridge to flatten and temperatures to cool slightly, dropping around 5 degrees.

The disturbance will bring westerly winds ranging between 10 and 20 mph Thursday afternoon combined with low humidity readings between 15% and 25% — approaching critical fire weather conditions.

Last month, meteorologists predicted a normal fire season this year and said despite last winter’s weak snowfall, above-average precipitation in May and June helped create a buffer and delay the wildfire season.

Dan Borsum, a Missoula-based forecaster with the Northern Rockies Coordinating Center, in June said residents should prepare for a warm, dry summer, and a wildland fire season that stretches past Labor Day.

While springtime precipitation and cool temperatures in May helped bolster the snowpack and delay runoff in the Flathead River Basin, hydrologists say below-average streamflows will likely persist through the summer.

According to the June 1 Water Supply Outlook Report, the Flathead River Basin is expected to be about 80% to 90% of normal total runoff volume through July while the Sun-Teton-Marias River Basin is expected to be at about 16% of normal.

The North Fork River in Polebridge on July 3, 2023. Hunter D’Antuono | Flathead Beacon

“Below-normal snowpack peak levels this season will likely have an impact on streamflow later this summer,” Eric Larson, a hydrologist with the USDA Natural Resource Conservation Service, said last month. “From a water-supply perspective, above-normal precipitation during the summer is almost always welcome and slower than normal melting of the remaining high-elevation snowpack would also help sustain closer to normal streamflows later in the summer.”

As of July 8, the streamflow of the North Fork Flathead River was running at 3,790 cubic feet per second (cfs), compared to the median flow of 4,620 cfs, according to U.S. Geological Survey data. The Middle Fork of the Flathead River was running at 3,910 cfs compared to the median of 4,570 cfs and is forecast to drop to 2,710 cfs by July 15.

Extreme heat increases the risk of heat exhaustion and heat stroke, especially for vulnerable groups such as children, older adults, people with chronic medical conditions, pregnant women, and pets. To reduce this risk, avoid strenuous activities, wear lightweight, loose-fitting and light-colored clothing that reflects heat, minimize direct sun exposure, drink water and stay in air-conditioned environments.

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