988 FXUS65 KMSO 221906 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 106 PM MDT Sun Jun 22 2025 .DISCUSSION... KEY MESSAGES: - Showers continue tonight and Monday. - Frost potential Monday morning. - A weak ridge builds in causing fair weather on Tuesday. - Transition to a thunderstorm pattern on late Wednesday that lasts into next weekend. An upper level low continues to spin over the region causing showers. Some locations, like Lemhi County, ID and Glacier National Park have picked up quite a bit of snow. As the low moves east this evening and tomorrow, showers will continue, but snow levels and temperatures will start to rise, so any remaining showers should be rain. In areas that clear out a bit tonight, cold temperature are a concern for Monday morning. The main area of concern is in the Bitterroot valley of Montana and near Salmon, Idaho. Further north in western Montana, there should be enough cloud cover with the shortwave coming through to prevent any frost impacts. Places like Seeley Lake, Ovando, and the higher elevation valleys of western Montana frequently get frost in June anyway, so it`s not really an impact there, but this would be a very late frost event for Salmon and the Bitterroot Valley, so we`ve issued a frost advisory for these valleys. By Tuesday a weak ridge builds over the region, but it is embedded in a broader trough pattern. As a result, there will still be some convection Tuesday, but we expect it will be a bit subdued and mostly over the mountains. On Tuesday temperatures will also rebound to slightly above average for this time of year and remain there for the rest of the week and into next weekend. Late Wednesday southwest flow returns to the region. Current forecasts have several shortwaves embedded in the southwest flow, and this is a classic pattern for thunderstorms in the region. With the warmer temperatures in place, plenty of recent moisture, and short waves moving through we expect scattered thunderstorm coverage most days through the weekend. There are no strong indicators of severe thunderstorms at this time, but depending on the timing of the shortwaves that is possibility. Characterizing the convection and whether or not there will be severe storms will be the main focus of our efforts this week. && .AVIATION...The upper level low over the region is moving eastward today. Moist northerly to northwesterly flow will continue over night causing some showers, especially near terminal KGPI. The main impact will be occasional showers and mid-level ceilings causing intermittent MVFR and IFR conditions. For back country fliers, the snow levels are rising, but low ceilings and fog / mist will likely impact back country air strips through at least Tuesday morning. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...Frost Advisory from 2 AM to 9 AM MDT Monday for Missoula/Bitterroot Valleys. ID...Frost Advisory from 2 AM to 9 AM MDT Monday for Eastern Lemhi County. && $$