Area Forecast Discussion
Issued by NWS Missoula, MT
Issued by NWS Missoula, MT
270 FXUS65 KMSO 251920 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 120 PM MDT Sat May 25 2024 .DISCUSSION...Shower activity will continue across the Northern Rockies through this evening into Sunday morning as a Pacific trough moves across the region. GOES Day Cloud imagery points towards a destabilizing atmosphere as evident by colder cloud tops and glaciating ice associated with showers. The best axis of instability will set up along the divide, where the HREF paints a a 15-20% probability for thunderstorms from 300-700pm MDT. High pressure will begin to build across the Northern Rockies Sunday, with a significant warming trend by Monday and Tuesday next week. Shallow moisture and instability will keep showers going across the terrain in northwest Montana Sunday. Confidence is high for temperatures to reach into the 80s Tuesday, with probabilities reaching 70-80% for valleys in western MT and central ID. The lowest valleys in Idaho and Clearwater County may even manage the 90 degree mark. The threat for organized thunderstorms increases Tuesday afternoon and evening. Forecast models suggest a Pacific trough will move onshore in OR/WA with southwesterly flow transporting an axis of instability across the Northern Rockies. Ensemble guidance, suggests the best axis of instability and shear will set up across the Camas Prairie of Idaho and along the ID/MT border. Instability (100-500 J/kg) and wind shear profiles (35-45kts) suggest storms may organize into multicellular line segments, with outflow winds and brief heavy rain being the primary storms threats. Forecast confidence decreases Wednesday into Thursday next week. Guidance is struggling with the amplitude and track of the aforementioned Pacific trough as it moves eastward. Roughly 40% of solutions suggest the trough will deepen into a closed low, with widespread precipitation and another round of snow across southwest MT and the higher elevations in ID, while the other members portray a weaker trough with higher snow levels and less precipitation. By Thursday, ensemble probabilities for 1" or more of snow reach 30-40% above 5,000 feet across central ID and southwest MT. /Lukinbeal && .AVIATION...Shower activity will continue across the Northern Rockies airspace through this evening into early Sunday morning as a Pacific trough moves into eastern MT. The atmosphere will continue to destabilize, with the best axis of instability setting up along the divide, where probabilities for thunderstorms hit 15-20% from 25/2000Z to 26/01000Z. /Lukinbeal && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$