FXUS65 KTFX 120533 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 1133 PM MDT Fri Apr 11 2025 Aviation Section Updated. .KEY MESSAGES... - Breezy and gusty winds today and Saturday, especially along the Rocky Mountain Front. - A slight chance for few showers and a thunderstorm for Southwest and Central Montana this evening. - Increasing chances for rain and snow Saturday through Sunday morning. - Drier weather and warming temperatures Monday and Tuesday. && .UPDATE... /Issued 823 PM MDT Fri Apr 11 2025/ Evening update has been published, with the main adjustment being to increase PoPs an additional 10-20% beyond 3AM MDT (09z) Saturday. Hi-Res guidance early this evening continues to support a band of moderate to heavy precipitation associated with and embedded shortwave/vort max lifting northeast and across portions of Southwest and Central Montana between 3AM MDT (09z) and noon MDT (18z) on Saturday. Snowfall rates of 1/4" to 1/2", with localized amounts approaching 3/4", will occur at and above mountain pass levels within this band of precipitation while lower elevations see predominately rain (although snow may mix in with the heaviest burst). Current suite of Winter Weather Advisories remain on track, but the overnight shift may need to consider adding the Little Belt and Highwood Mountains should precipitation overspread these areas sooner, which would allow for slushy accumulations on road surfaces prior to them (road surfaces) warming adequately to melt the snow. - Moldan && .DISCUSSION... /Issued 823 PM MDT Fri Apr 11 2025/ - Meteorological Overview: Breezy and gusty winds persists through the rest of the afternoon today. Increasing moisture and a weak upper-level disturbance moving through will produce a slight chance develop a few showers and a low chance for an isolated thunderstorm this afternoon and evening in Southwest and Central MT. Chances for precipitation increases Saturday morning along the cold front for Central and Southwest MT. A vorticity maximum at 500mb and PWAT's around 0.4-0.5" will develop a band of wetting precipitation stretching from western Beaverhead County to Fergus County. Rain will fall across lower elevations, with mountain passes getting wet snow. Weak instability builds in Saturday afternoon, which allows for a low end chance for a few thunderstorms to develop in the Southwest. Stronger winds aloft from the system will bring another round of gusty winds to the Rocky Mountain Front and breezy winds elsewhere. A dry slot moving in behind the front will allow for a brief lull in precipitation in the afternoon before late Saturday night and Sunday morning. Another wave of precipitation wrapping around the low pressure system will bring additional mountain snow, with some light snow mixing in at lower elevations. Snow quickly diminishes Sunday afternoon. A ridge building in will warm temperatures up and bring dry weather Monday and Tuesday. Ensembles hint at a brief breakdown of the ridge Wednesday, which brings a low end chance for precipitation. - Forecast Confidence & Scenarios: Precipitation Saturday: There is a good chance for wetting precipitation with showers/snow Saturday with the moist atmosphere and enhanced forcing along the front. There's a 50-80% for 0.1" of moisture for areas along and south of the Montana Highway 200 corridor, and a 40-60% chance for 0.25" of precipitation in Central MT (where the widespread band of precipitation looks to set up Saturday morning). For Mountain passes, the main concern is moderate to heavy bursts of snow quickly creating slushy road conditons Saturday morning. 1-3" of quick hitting snow will provide variable road conditons and reduced visibilities for travel. Therefore, A Winter Weather Advisory was issued to account for these minor driving impacts on Boulder Hill, Homestake Pass, and Chief Joseph Pass. The Little Belts, will also get this quick hitting snow. However, they will be impacted in the late morning/afternoon, where pavement temperatures look to be warm enough for the snow to melt off. An earlier start time may warrant an advisory in a future forecast. Precipitation Sunday: There's a 30% chance for 6" of snow along King's Hill Pass Sunday, and about a 30-70% for 2" of snow along the Montana Highway 200 corridor between Armington Junction and Stanford. Winds gusting to 40 mph at times can also reduce visibility with snow. Since this is a quick hitting system, there remains some uncertainty in exact amounts due to timing, especially for the northerly upslope regions. The lower elevations will see light snow mix in Sunday morning, but little to no snow accumulations are expected. -Wilson && .AVIATION... 12/06Z TAF Period VFR conditions will prevail at the KHVR, KGTF, KBZN, and KEKS terminals during the duration of this TAF period. However there is a 20% chance for a thunderstorm between 12/21Z and 13/00Z at the KEKS and KBZN terminals which would reduce visibility and ceilings to MVFR levels. At the KGTF terminal there is a 25 - 50% chance for rain between 12/10Z and 12/21Z. At the KHVR and KLWT terminals there is a 20 - 50% chance for rain from about 12/19Z through the end of this TAF period. At all terminals after 12/18Z it will be windy. Between 12/12Z and 12/18Z there will be isolated instances of low- level wind shear and mountain wave turbulence across Southwestern Montana. -IG Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PRELIMINARY POINT TEMPS/POPS... GTF 42 57 34 48 / 40 50 60 30 CTB 35 53 28 46 / 0 20 80 10 HLN 42 55 33 51 / 70 80 20 40 BZN 39 52 27 47 / 40 90 40 20 WYS 32 54 18 44 / 30 90 40 10 DLN 41 57 25 49 / 30 70 10 0 HVR 35 60 32 50 / 10 30 80 30 LWT 37 50 29 42 / 60 90 50 40 && .TFX WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 3 AM to noon MDT Saturday for Elkhorn and Boulder Mountains-Northwest Beaverhead County. && $$ http://www.weather.gov/greatfalls