936 FXUS65 KTFX 050502 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 1102 PM MDT Wed Jun 4 2025 Aviation Section Updated. .KEY MESSAGES... - Showers and isolated thunderstorms will decrease this evening with a few isolated showers and weak thunderstorms possible again each afternoon through Saturday. - Temperatures gradually warm to above seasonal averages by the weekend with the warmest conditions expected on Monday. - A transition back to seasonal temperatures with opportunities for precipitation is expected next week. && .UPDATE... /Issued 820 PM MDT Wed Jun 4 2025/ Shower activity will continue to diminish this evening with the loss of diurnal heating, but a shortwave trough overhead will maintain some cloud cover and a stray shower or two, mostly along the Rocky Mountain Front. There will also be some patchy fog late tonight into Thursday morning, particularly over and near river valleys. A modestly unstable northwesterly flow aloft will remain in place on Thursday for another round of scattered afternoon showers and perhaps a few thunderstorms. - RCG && .DISCUSSION... /Issued 820 PM MDT Wed Jun 4 2025/ - Meteorological Overview: Area remains beneath cyclonic NW flow aloft within the broad circulation of an upper level trough centered near Hudson Bay. Subtle shortwave disturbances moving through the NW flow and daytime instability beneath relatively cool air aloft has led to the development of scattered showers with the possibility of a few weak thunderstorms and similar development is expected Thursday afternoon. Gradual warming aloft will lead to increased stability with a more limited coverage of isolated showers and thunderstorms by Friday and Saturday. An upper level ridge shifts inland later this weekend and across the Northern Rockies on Monday. Temperatures warm to well above average by Monday beneath the upper ridge and are likely to remain warm on Tuesday as a southwest to westerly flow develops as the ridge progresses east of the area. Longer range model ensembles generally support a more zonal flow with some embedded moisture developing by the middle of next week with potential for deeper troughing moving onshore late next week. There is still a wide spread in details but a transition back to more seasonal temperatures with increased chances for showers and thunderstorms is likely as this pattern develops mid-late next week. - Forecast Confidence & Scenarios: High resolution/short range model ensembles give areas along the Rocky Mountain Front and over the Little Belts the highest risk (30- 50%) for lightning this afternoon with much lower probabilities (15% or less) across the plains and valleys. Similar probabilities for lightning are forecast for late Thursday with most southwest MT mountain ranges also having a 20-40% risk for lightning. There is a 30-50% chance that maximum temperatures reach or exceed 90F on Monday, primarily across portions of north-central MT below 4000 ft (Great Falls, Cut Bank, Havre) while probabilities are 20% or less elsewhere including Helena, Lewistown and Bozeman. Hoenisch && .AVIATION... 05/06Z TAF Period VFR conditions will prevail across all terminals during this TAF period with light and variable winds and scattered to few high-level clouds outside of any rain showers. At the KWYS, KHLN, KEKS, KBZN, and KLWT terminals there is a 15 - 30% chance for rain showers between 05/18Z and 06/00Z. Between 05/18Z and 06/00Z there is a low chance (< 10%) for an isolated rain shower at the KCTB, KHVR, and KGTF terminals. During any rain shower ceilings will briefly lower to low-VFR levels. At the KLWT terminal there is a 15% chance for a thunderstorm between 05/18Z and 05/21Z. Any thunderstorm will bring frequent lightning and gusty, erratic winds. At the KWYS terminal between 05/11Z and 05/13Z there is a low chance (< 10%) for patchy fog to form. During any rain shower there will be a brief period of mountain obscuration. -IG Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PRELIMINARY POINT TEMPS/POPS... GTF 37 72 46 80 / 20 10 0 0 CTB 38 73 45 78 / 20 10 0 0 HLN 45 75 48 81 / 20 20 0 0 BZN 38 70 41 78 / 10 20 0 0 WYS 29 65 30 70 / 10 30 10 10 DLN 36 68 41 76 / 0 20 0 0 HVR 42 75 46 83 / 20 10 0 0 LWT 40 67 43 75 / 40 30 0 0 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ http://www.weather.gov/greatfalls