textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Warmest temperatures of the summer this weekend through early next week. Elevated heat risk for those sensitive to heat, especially those without cooling/hydration.

- Low relative humidity and increased west winds will result in elevated fire weather concerns on Saturday and Sunday, especially in southwest Montana.

High pressure will build across western Montana and north central Idaho beginning today into the weekend. Thunderstorm activity will generally decrease today, with the only notable chances confined to the southern tip of Lemhi County in Idaho. By Friday evening, atmospheric conditions will become more unstable, bringing another round of potential thunderstorms. These storms will mainly focus over southwest Montana and Lemhi County, carrying the threat of strong, gusty winds between 40 and 50 mph.

Temperatures will surge on Saturday and remain unseasonably hot into early next week. Valleys across western Montana can expect daytime highs in the 90s, while lower elevation areas like Hells Canyon and the lower Salmon River valleys will likely reach triple digits. Forecast models indicate a high confidence (70 percent) of moderate heat impacts for valleys along and east of Highway 93, meaning individuals sensitive to heat may be adversely affected. There is also a 30 percent chance of major heat impacts that could affect anyone lacking adequate cooling and hydration. In addition to the heat, strong upper-level winds combining with low daytime humidity will create near-critical fire weather conditions in southwest Montana and Lemhi County this Saturday and Sunday. For those recreating outdoors this weekend, please prioritize safety: stay consistently hydrated, take frequent breaks in the shade, avoid strenuous activities during peak afternoon heating, and practice extreme caution to prevent any sparks or fire starts in these dry, windy conditions.

A significant pattern change is expected next week as a surge of moisture moves into the region from the south. This will elevate the risk for widespread, rain-producing thunderstorms across western Montana and north-central Idaho by midweek, offering a stark contrast to the dry and windy weekend conditions. Initially, this moisture will arrive in the mid and upper levels of the atmosphere. Because the air near the surface will still be very dry, the first storms that develop early next week may produce very little rainfall at the ground but will be highly capable of generating strong, erratic outflow winds.

AVIATION

High pressure building across western Montana and north-central Idaho will maintain predominantly VFR conditions across regional terminals through the forecast period. For this afternoon, surface winds will generally prevail from the west to northwest at 5 to 10 knots, with localized gusts up to 20 knots expected, particularly across western Montana terminals. Thunderstorm activity today will be minimal, with any isolated convective development restricted to the far southern portions of Lemhi County. On Friday, increasing atmospheric instability by the evening hours will introduce a renewed risk of thunderstorms. Convective activity will remain primarily focused over southwest Montana and Lemhi County (KBTM and KSMN), with any developing storms capable of producing strong, erratic outflow winds gusting between 35 and 45 knots.

MSO WATCHES/WARNINGS/ADVISORIES

MT...None. ID...None.