FXUS65 KTFX 092057 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 257 PM MDT Fri May 9 2025 .KEY MESSAGES... - The warming and drying trend will peak on Saturday with maximum temperatures approaching daily records and gusty southwest winds developing in the afternoon. - Scattered thunderstorms Saturday afternoon and evening could produce strong wind gusts with a few isolated cells producing small hail. - Showers and thunderstorms become more widespread on Sunday with a few strong to severe thunderstorms possible in the afternoon. - Cooler and wetter conditions develop early next week with a spring storm system likely to bring widespread rain and higher elevation snow to parts of central and southwest Montana Tuesday and Wednesday. && .DISCUSSION... - Meteorological Overview: The area remains on the NW periphery of an upper level ridge with axis extending from the SW US into the Northern Plains states with dry and mild conditions persisting tonight. On Saturday, southwest flow aloft increases as the ridge begins to shift east ahead of an upper level trough moving toward the west coast. Deep mixing and the increased flow aloft will result in breezy to locally windy conditions developing Saturday afternoon as temperatures warm to near daily records at many lower elevation locations. The combination of increasing mid-level moisture and instability will lead to the development of thunderstorms across central ID and SW MT, which track northeast across central and n-central MT Saturday afternoon and evening. Storm motion should be fairly quick on Saturday with available moisture keeping thunderstorm coverage scattered and precipitation pretty brief. The primary risk with tomorrows thunderstorms will be strong wind gusts as an initially deep and dry boundary layer support enhanced downdraft/outflow winds. Additional rounds of showers and thunderstorms move across the region Sunday as deeper and moisture and embedded shortwave disturbances eject out of the offshore trough moving onto the west coast. Temperatures begin to cool Sunday as well but remain warmer than average until the larger scale trough moves inland on Monday. There is some larger scale support for organized/strong thunderstorms on Sunday from somewhat diffluent mid level flow and upper level jet energy moving in ahead of the trough but still some uncertainty with the degree of instability and timing of an embedded frontal feature moving across the Northern Rockies. - Forecast Confidence & Scenarios: High resolution ensemble guidance focuses much of tomorrow's convection along an axis centered from Jefferson county northeast through Hill and Blaine counties where the risk for thunderstorm gusts in excess of 50kts ranges from 10-30%. The larger scale trough moves across the region Monday through much of next week with medium range model ensembles generally supporting an embedded mid-upper level low lifting from the Northern Great Basin across MT and WY in the Tue/Wed period. There are still some differences in specific track and timing of this feature leading to some uncertainty in the northern extent of widespread precipitation but this is a favorable track for precipitation across much of southwest and central MT. Cooling by Tuesday and Wednesday will also support some higher elevation snow down to at least 7000 ft, but impacts/accumulation below this level are still somewhat uncertain. Hoenisch && .AVIATION... 09/18Z TAF Period VFR conditions will prevail at all terminals during the duration of this TAF period with mostly scattered mid/high level clouds. Between 10/18Z and 11/00Z there is a 10% chance for a thunderstorm at the KBZN terminal. Any thunderstorm will bring lightning, and gusty, erratic winds. -IG Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PRELIMINARY POINT TEMPS/POPS... GTF 50 87 51 78 / 0 40 30 50 CTB 46 82 48 72 / 0 20 20 60 HLN 51 87 53 80 / 0 50 30 60 BZN 46 84 50 75 / 0 10 20 60 WYS 34 75 43 66 / 0 10 20 70 DLN 46 80 50 73 / 0 30 10 40 HVR 49 90 50 80 / 0 20 40 40 LWT 52 84 53 77 / 0 20 40 50 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ http://www.weather.gov/greatfalls