FXUS65 KMSO 091934 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 134 PM MDT Thu Jul 9 2026 .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. One change to the forecast: Added a slight chance for night-time thunderstorms Friday night from north-central Idaho into northwest Montana. Models are depicting just enough elevated moisture and instability with a wave that could trigger storms. Multiple ensemble members depict this as well. The main impacts would be lightning and gusty outflow. 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. We issued heat advisories for the Hells Canyon, Salmon River Valley, Lowell to Moose Creek, and lower valleys of Lemhi County into the weekend. These are the areas that would see the hottest temperatures possibly getting up to 107 degrees. Also night-time temperatures may not recover very well, only in the 60s. The reason for not issuing heat advisories for other locations is the fact that there is a low threat for record highs being matched and there will be a decent cooldown each night. The forecast has been running too warm at night so we have trimmed the forecast down to account for that bias. Looking at climatology, we need the heat ridge to be more centered over the western U.S. and over our region, rather than centered over the Northern Plains, to realize a scenario with hotter temperatures.(i.e. Butte getting to 95 degrees or hotter). Another potential impact from the large ridge setting up east of us is that the flow will start to bring up wildfire smoke from the Four Corners region by Sunday into Monday. The latest experimental smoke model, RRFS-SD model, is starting to depict that. We've already noticed an increase of haze in the last several days, so by Monday there may be an uptick the amount of haze lingering in the mountains. A significant 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 and lightning. && .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...ID...Heat Advisory from noon MDT /11 AM PDT/ Saturday to 9 PM MDT /8 PM PDT/ Sunday for Eastern Lemhi County...Southern Clearwater Mountains...Western Lemhi County. Heat Advisory from 11 AM Friday to 8 PM PDT Sunday for Lower Hells Canyon/Salmon River Region. && $$