FXUS65 KMSO 240920 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 320 AM MDT Sun May 24 2026 .DISCUSSION... KEY MESSAGES: - Warming and drying trend through the today and tomorrow. - Thunderstorms return to western Montana tomorrow and Tuesday. - An upper low arrives tomorrow into Tuesday causing a cool down and active, wet weather the rest of the week. A warming and drying trend under a broad, weak ridge will last through tomorrow. Temperatures will rise to about 15 degrees above average by tomorrow. Models have trended earlier in their timing for thunderstorms ahead of the cold front for tomorrow night. As a result more locations in western Montana will see thunderstorms tomorrow afternoon. The showers and thunderstorms spread across central Idaho and even into northwest Montana by tomorrow evening. Ensembles agree very well on a closed upper level low moving into the region late tomorrow into Tuesday. This will cause a drop in temperatures to about 5 degrees below average for this time of year on Tuesday. The most uncertainty remains in the precipitation amounts that the region will receive. These values are heavily dependent on how fast the upper level low moves and exactly what track it takes, though trends in the ensembles are favoring more rain for western Montana and particularly southwest Montana. After the sharp cool down on Tuesday, temperatures will trend warmer the rest of next week with active weather as the upper level low stumbles out of the region. Ensemble guidance has also been trending wetter for the rest of the week as more members are favoring a slower transition out of the region. && .AVIATION...A broad and weak ridge continues to dominate the weather across the northern Rockies this weekend. Some river fog is expected near terminals KMSO and KGPI. There is about a 30 percent chance that the fog will impact terminal KGPI this morning. Otherwise, VFR conditions are expected across the region today. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$