390 FXUS65 KTFX 220233 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 833 PM MDT Sat Jun 21 2025 .KEY MESSAGES... - Precipitation becomes more widespread this evening after a lull throughout much of the day, with precipitation lingering into the afternoon and evening hours on Sunday. - Temperatures will be well below normal on Sunday, with some locations struggling to warm out of the 40s. - Freezing temperatures are becoming more likely across the valleys of Southwest and Central Montana Sunday night and into Monday morning. - A return to more typical June conditions expected by the middle of next week. && .UPDATE... The primary change this evening was to lower snow levels to the valley floors in Southwest Montana with the cold core of the Pacific low moving directly over this area late tonight into Sunday morning. This added the mention of snow in the higher valleys above 5,000 ft. A special weather statement was sent out earlier to address the minor expected impacts and the situation will continue to be monitored should the snow come in a little heavier than expected. Winds along the Hi- Line from Cut Bank to the Sweet Grass Hills area are now in the decreasing phase, though a few gusts are still approaching and exceeding the 50 mph mark. So the high wind warning was left as is for now. No other changes were made other than routinely refreshing the winter weather statements. - RCG && .DISCUSSION... /Issued 145 PM MDT Sat Jun 21 2025/ - Meteorological Overview: An anomalously strong summer storm will continue to bring widespread impacts to the Northern Rockies through Sunday night. These impacts include but are not limited to : accumulating snow to as low as 5000- 6000ft across all of Southwest through North Central Montana; high winds along and north of the Hi-Line in North Central Montana; and cold (for June) temperatures with the potential for overnight lows to fall below freezing across lower elevations. Outside of Glacier, Toole, and Pondera Counties most areas have seen a break from the precipitation today, with the strong and gusty west winds being the biggest story of the day. By this evening the lull in precipitation will come to an end as rain and mountain snow begin to overspread Southwest Montana, with the precipitation shield over northwestern portions of North Central Montana (i.e. Glacier, Pondera, Teton, and Toole) Counties beginning to pivot south and east towards Central Montana. These two areas of precipitation will expand in coverage through the remainder of the overnight hours, with widespread rain and mountain snow expected southeast of a Havre to Dupuyer line through the afternoon/early evening hours on Sunday. Most lower elevations through this timeframe can expect to see between 0.25-0.5" of QPF, with the mountains of Southwest Montana seeing liquid equivalents of between 0.5-1" and the Continental Divide north of Teton Pass seeing between 0.5-1.5". - Moldan From Monday through next Saturday, a return to more typical June conditions is expected. Afternoon temperatures will warm to slightly above normal readings by Wednesday, which will then continue into next weekend. The chance for showers/thunderstorms will become more isolated as we go later into the week. There will be chances for thunderstorms, but the overall strength of the upper level disturbances to produce the precipitation will be on the weaker side, thus the more isolated potential for storms. - Brusda - Forecast Confidence & Scenarios: Main area of uncertainty that continues to exist within the forecast over the next 24 hours will be snow levels across Southwest and Central Montana as the cold and deep upper level low moves over these areas. Current forecast has largely incorporated the NBM 10th Percentile for snow levels, which generally lowers most locations across Southwest through Central Montana to around 6000 feet. While this 10th Percentile would appear to be a reasonable lowest possible snow level, recent June snowstorms dating back to 2020 would suggest that even these levels may still be 1000-2000 feet too high. Given these past experience an additional 500-1000 feet were taken off of the NBM 10th Percentile snow levels, but even this reduction still keep the valley floors as rain. For now we will hold off on any Winter Weather Advisories for the valley floors of Central and Southwest Montana, but a short notice advisory may be needed should levels crash quickly tonight. Main impact to the valley floors would be snow accumulating on foliage, which could lead to isolated power outages. With most road surfaces being well above freezing accumulations here would be slushy at best. - Moldan && .AVIATION... 22/00Z TAF Period Areas of widespread precipitation and MVFR/IFR/LIFR conditions will slowly develop from north to south after 22/03Z and persist through much of the remaining TAF period. Gusty west to northwesterly winds over the plains will become more northerly and slowly diminish after 22/06Z. - RCG Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PRELIMINARY POINT TEMPS/POPS... GTF 41 47 37 67 / 60 100 70 40 CTB 38 50 36 62 / 90 70 30 70 HLN 43 49 37 69 / 70 100 50 30 BZN 39 49 32 68 / 90 90 30 10 WYS 32 45 24 61 / 80 100 70 10 DLN 31 46 30 63 / 90 90 30 10 HVR 43 50 39 67 / 30 100 80 40 LWT 38 46 34 65 / 60 90 70 20 && .TFX WATCHES/WARNINGS/ADVISORIES... High Wind Warning until 3 AM MDT Sunday for Eastern Glacier, Western Toole, and Central Pondera-Eastern Toole and Liberty. Winter Storm Warning until noon MDT Sunday for East Glacier Park Region. Winter Weather Advisory until noon MDT Sunday for Big Belt, Bridger and Castle Mountains-Elkhorn and Boulder Mountains- Gallatin and Madison County Mountains and Centennial Mountains- Little Belt and Highwood Mountains-Northwest Beaverhead County- Ruby Mountains and Southern Beaverhead Mountains-Southern Rocky Mountain Front. && $$ http://www.weather.gov/greatfalls