FXUS65 KTFX 050619 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 1115 PM MST Mon Mar 4 2024 UPDATED AVIATION SECTION .SYNOPSIS... After tapering off this evening, snowfall returns to Southwestern Montana on Tuesday as a fast moving weather system moves across the Snake River Valley. Further north, expect temperatures to moderate a bit with most areas seeing temperatures in the mid 30s. Beyond tomorrow, expect temperatures to warm up across the area through the end of the week. && .UPDATE... 8 PM Update...Adjusted overnight lows towards current trends, with w ind chill values around 15 below for areas north of Highway 2 overnight. Otherwise, light snow showers moving from west to east across the CWA are starting to diminish a bit. That trend should continue for most areas, expect the Rocky Mountain Front where they will continue overnight. A band of snow moving through the West Yellowstone area currently, should also diminish in a bit, with a break in the snow in this area until the next system arrives on Tuesday morning. Blowing snow could also be an impact on Tue, especially for areas south of I-90 from Butte to Bozeman. Brusda 6 PM Update...Forecast updated for this evening. Heavy snow is falling in the West Yellowstone area, so the start time for the winter weather advisory has begun for that area, with snow accumulations up to 5 inches expected tonight. Overnight lows were adjusted a bit colder over North Central MT, as daytime highs today did not get as warm as forecasted. Brusda && .AVIATION... 1115 PM MST Mon Mar 4 2024 (05/06Z TAF Period) North Central Montana (KCTB KHVR): Low clouds and patchy fog will continue to spread south over the Hi-Line through 09Z, bringing mainly mountain-obscuring MVFR conditions. Ceilings are forecast to lift and break up between 15Z and 18Z, leaving VFR conditions with passing high- and mid-level cloudiness through 06/06Z. Winds will generally be light, but gusts to 35 kt are possible close to the Rocky Mountain Front through around 18Z, also with periods of low level wind shear there through 12Z. Central Montana (KGTF KLWT KHLN): VFR conditions are forecast to continue through at least 06/06Z with passing high- and mid-level cloudiness. However, a disturbance will move east through the area between 12Z and 00Z, which could bring some mountain top obscuring snow showers. Otherwise, surface winds should remain light. Southwest Montana (KBZN KEKS): VFR conditions will continue until around 12Z, then a disturbance will lower conditions to mostly low VFR/MVFR after 15Z or so in snow showers with mountain obscuration; periods of IFR conditions are also possible, especially after 21Z. Southerly surface winds will also increase south of Interstate 90 between 14Z and 20Z, producing gusts in the 25 to 40 kt range on ridge tops and through south-north oriented valleys, and causing low level wind shear with westerly winds aloft causing mountain wave turbulence. -Coulston Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PREV DISCUSSION... /ISSUED 553 PM MST Mon Mar 4 2024/ Key points: -Snow showers continue across Southwestern Montana today and Tuesday -Warmer and drier weather is expected for the second half of the week Short Term (through Tuesday)... Scattered snow showers are expected across Southwestern Montana as the warm March sunshine destabilizes a cold air mass across the area. We will have to watch these this afternoon for a few heavier snow showers that could put down a quick half inch or so and cause brief reductions in visibility to under a mile at times, but the overall disorganized nature of these snow showers should help to keep impacts isolated. As we head into the day on Tuesday, a low pressure system moving along a stationary front will push through Southwestern Montana, bringing a round of mostly light to moderate snowfall across areas along and near the Montana-Idaho border. With that said, there could be an area along the stationary front that sees enhanced snowfall, with periods of heavy snow with under a half mile visibility and snowfall rates in excess of 1 inch/hour. At this time, it appears that the greatest risk for this type of snowfall is south of a line from Bozeman to Dillon. While I am holding off on any sort of upgrade to a Winter Storm Warning at this time, should this band set up some areas could see in excess of a foot of snowfall thanks to the orographic and frontogenetic (mountain- induced and front-induced, respectively), forces at play. Snowfall amounts were nudged upwards to account for this possibility. Extended (Wednesday through next Monday)... On the heels of this system, expect clearing skies across the area as surface winds turn westerly/southwesterly thanks to building upper level ridging. With this ridge in place through the end of the week, expect temperatures to moderate to near to near to above average temperatures across the area with breezy, but otherwise tranquil, conditions across the area. Our upper level ridge will begin to break down as we head into next week, which will allow for a more active pattern to set up for the beginning of next week. Ludwig && .PRELIMINARY POINT TEMPS/POPS... GTF 7 36 14 37 / 10 0 0 0 CTB -3 29 6 31 / 0 0 0 0 HLN 12 33 14 35 / 20 20 10 0 BZN 7 29 13 33 / 40 40 40 10 WYS 1 27 9 29 / 90 90 80 50 DLN 5 30 14 32 / 20 40 30 10 HVR -2 21 6 23 / 10 0 10 10 LWT 11 32 12 32 / 30 10 10 10 && .TFX WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 5 AM MST Wednesday for Gallatin and Madison County Mountains and Centennial Mountains. Winter Weather Advisory from 5 AM Tuesday to 5 AM MST Wednesday for Madison River Valley-Ruby Mountains and Southern Beaverhead Mountains. && $$ http://www.weather.gov/greatfalls