


Area Forecast Discussion
Issued by NWS Missoula, MT
Issued by NWS Missoula, MT
276 FXUS65 KMSO 141928 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 128 PM MDT Mon Jul 14 2025 .DISCUSSION... KEY MESSAGES: - Hot today with risk for heat related impacts in north-central Idaho - A potent storm with unusually cold, wet, and windy conditions this evening into Tuesday. - Mostly dry rest of the week, warming back up to near and above normal. Hot temperatures continue this afternoon with many locations warming well into the 90s (triple-digits in the valleys of north-central Idaho). Satellite and webcam imagery this afternoon shows a dispersed area of elevated smoke drifting slowly eastward out of the state of Washington due to active wildfires in that region. Surface- based air quality observations indicate some areas of deteriorating air quality toward the Moderate category in far northwestern Montana. A very unusual storm for this time of year is forecast to move into the Northern Rockies later this evening through Tuesday. An upper-level disturbance is noted on water vapor imagery slowly moving south and east through British Columbia. This disturbance is pulling in anomalous amounts of precipitable water, near and in excess of 1, from the Pacific Ocean. HYSPLIT backward trajectory modeling, for upstream locations, helps identify the Northern Pacific / Canadian Arctic source of the unseasonably cold air which is being pulled in on the backside of this disturbance. As the upper level trough swings through the Canadian border later this evening, the mid-level low continues to amplify and nearly cuts off completely from the associated upper level jet as it pushes into our region. At the surface, a strong cold front will continue to mature becoming increasingly thermally-packed. This front will induce a strong northeasterly to southwesterly pressure gradient across the divide through much of the day on Tuesday forcing north and easterly winds over and through mountain gaps similar to a wintertime Arctic cold front. In this environment, stronger thunderstorms will be able to produce near severe-level gusts with background winds already elevated in the 20-30 mph range. Recreators on area lakes should heed wind advisories due to the potential for large waves and generally choppy/unfavorable conditions. Ample moisture availability will help induce shower and thunderstorm development overnight into Tuesday with heavy rainfall and small hail potential. There is concern for localized flooding due to heavier rainfall and mudslide or debris flows in steep terrain or within and downstream of burn scar perimeters. A wide range in potential rainfall accumulation exists due to the convective nature of showers. Generally, 0.2-0.5" of rainfall is expected across a widespread area north of I-90 with some locations potentially seeing up to 2.0" of rainfall such as Glacier N.P., nearby mountains of northwest Montana, and along the Continental Divide. Some snow may mix down as low as 8,500ft in the Glacier Region though widespread measurable snowfall remains unlikely. A 20-30 degree drop in daytime highs from today to tomorrow will bring some locations close to record cool high temperatures for the date. Backcountry users should take into account the cold, wet, and windy conditions to reduce any risk of prolonged exposure or hypothermia. Heading into the rest of the week, a moderating trend in the weather will follow with daytime highs back near and above normal. Another disturbance, albeit almost completely dry, will pass through the region on Thursday bringing another slight uptick to winds. Warming continues into the weekend. && .AVIATION... A disturbance dropping into the Northern Rockies from Canada continues to drive gusty winds of 20-30 knots across north-central Idaho and western Montana. Expect a significant change later this afternoon or early evening as a potent cold front sweeps through. This front will usher in strong northeasterly winds to Kalispell (KGPI), with gusts projected to intensify to 35-45 knots beginning between 15/0300-0500Z. The northeasterly wind shift will progress southward throughout the evening and overnight, eventually reaching Missoula (KMSO) and Butte (KBTM) by early Tuesday morning. In addition to the strong winds, sufficient instability accompanying the frontal passage will spark thunderstorm development across northwest Montana, including the Kalispell (KGPI) area. These storms will be capable of producing small hail, heavy rain, and frequent lightning. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...Wind Advisory from 5 PM this afternoon to 2 PM MDT Tuesday for Flathead/Mission Valleys...Kootenai/Cabinet Region...West Glacier Region. Wind Advisory from 9 PM this evening to 8 PM MDT Tuesday for Bitterroot/Sapphire Mountains...Butte/Blackfoot Region... Lower Clark Fork Region...Missoula/Bitterroot Valleys... Potomac/Seeley Lake Region. ID...Heat Advisory until 8 PM PDT this evening for Lower Hells Canyon/Salmon River Region...Orofino/Grangeville Region. && $$