Area Forecast Discussion
Issued by NWS Missoula, MT
Issued by NWS Missoula, MT
199 FXUS65 KMSO 290941 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 341 AM MDT Fri Aug 29 2025 .DISCUSSION... KEY MESSAGES: - Locally dense fog may reduce visibility this morning, especially along and south of Interstate 90 and in the valleys of north- central Idaho - Thunderstorms capable of heavy rainfall this afternoon in northwest Montana - Warming and drying trend this weekend Lingering low-level moisture will support dense valley fog formation by morning where skies have cleared overnight, generally along and south of the I90 corridor. The exiting trough will focus shower and thunderstorm activity over northwest Montana this afternoon. Weak steering flow will promote slow-moving storms capable of heavy rainfall, with rates potentially exceeding 0.75 inches per hour. This could lead to localized runoff issues, particularly in steep terrain and flood prone basins. Model guidance indicates a 20-30% probability of such rates occurring in Glacier National Park. A significant pattern change arrives this weekend as an upper- level ridge builds over the region. This will bring an end to precipitation and initiate a pronounced warming trend. Dry and progressively warmer conditions are expected through the weekend and much of next week, with high temperatures climbing 10-15F above seasonal normals. && .AVIATION...Low level moisture from rain showers on Thursday has allowed for a mix of stratus and valley fog to develop this morning for many areas in western Montana and north central Idaho. Locally dense fog currently exists along portions of the I90 corridor including at KBTM and periodically at KMSO. Anticipated locally lowered visibility and ceiling through roughly 29/1500z. Chances for afternoon showers and thunderstorms will exist primarily in northwest Montana, with KGPI having the best chance (30-40 percent). The slow moving nature of storms will make heavy rain and lightning the main threats with any storms that develop. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$