FXUS65 KTFX 201145 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 545 AM MDT Wed Aug 20 2025 Aviation Section Updated. .KEY MESSAGES... - Warm today with a chance for scattered showers and thunderstorms in the afternoon and evening. - Cooler and more seasonable temperatures expected Thursday through the weekend. && .DISCUSSION... /Issued 305 AM MDT Wed Aug 20 2025/ - Meteorological Overview: The upper level ridge will start to break down this afternoon and evening as a trough moves through across central and southern Canada. An associated cold front will make its way across the region allowing for scattered showers and thunderstorms through the late evening hours. Similar to previous days, the main concerns will be gusty, erratic winds and lightning with small hail being a secondary threat today. Behind the cold front, cooler and more seasonable temperatures will persist through the weekend. An upper level ridge will start to build over the western CONUS which will bring northwesterly flow to the region and, depending on exactly where the ridge sets up, may bring a chance for afternoon showers and thunderstorms to the region, particularly across southwestern Montana. - Forecast Confidence & Scenarios: Regarding thunderstorms this afternoon, there is still some lingering uncertainty as to how exactly this event will play out. The NBM remains very dry while hi-res guidance brings in the first showers and thunderstorms along the Montana/Idaho border as early as 10 AM to 12 PM in some cases and slowly spreading northward while precipitation coverages also fill in along the Hi-Line as the cold front approaches. The concern, particularly across southwestern Montana, will be how dry these thunderstorms end up being. Model soundings have pointed to drier thunderstorms south of the I-90 corridor with increasing PWATs. A mix of wet and dry thunderstorms is expected across central and north-central Montana which may bring some localized heavier rain but otherwise these storms are expected to bring little in the way of accumulation. Rather instead gusty, erratic winds and more lightning is expected which will be a concern for fire weather concerns. -thor && .AVIATION... 20/12z TAF Period Lingering SHRA across the area this morning will dissipate by 15z, but should not bring impacts to terminals aside from some downdrafts and LLWS near the showers. While winds will be light early today, expect gusts to 25kts or so across the plains by the mid to late afternoon. Another round of SHRA and TSRA will develop during the late afternoon and evening hours today. While any terminal could be impacted from these SHRA/TSRA and their outflows, the most likely terminals to see these are from KGTF and KLWT points south. Ludwig Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .FIRE WEATHER... Critical fire weather concerns are expected this afternoon across portions of southwest Montana with highs in the upper 80s to low 90s, minimum RH values as low as 12%, winds gusting up to 30 mph, and the potential for dry thunderstorms in the afternoon. Elevated fire weather concerns are expected across the remainder of the region with highs across the plains reaching up into the low 90s, minimum RH values in the upper teens to low 20s, winds gusting up to 20 mph, and a chance for thunderstorms in the late afternoon through the evening. A cold front will pass through this afternoon into Thursday which will allow for temperatures to cool down and allow for better overnight recovery heading into Thursday and Friday which will, at least temporarily, ease some of the worst concerns. -thor && .PRELIMINARY POINT TEMPS/POPS... GTF 91 54 80 53 / 10 100 0 CTB 85 48 76 47 / 10 0 0 0 HLN 90 56 85 52 / 10 20 0 0 BZN 93 51 85 48 / 10 20 0 0 WYS 84 41 82 39 / 20 20 0 0 DLN 89 48 84 47 / 20 20 0 0 HVR 92 53 78 49 / 10 20 0 0 LWT 86 53 76 51 / 10 30 0 0 && .TFX WATCHES/WARNINGS/ADVISORIES... && $$ http://www.weather.gov/greatfalls