FXUS65 KTFX 091209 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 509 AM MST Thu Jan 9 2025 Aviation Section Updated. .KEY MESSAGES... - Winds will increase this evening along the Rocky Mountain Front and adjacent plains and spread to the plains of North-Central and Central Montana Friday morning continuing through Friday night. - There will be primarily mountain and mountain adjacent snow Friday evening through Monday morning with the heaviest snowfall Saturday evening through Sunday morning. - Temperatures will warm up to well-above seasonal averages by the middle of next week. && .DISCUSSION... /Issued 324 AM MST Thu Jan 9 2025/ - Meteorological Overview: Today an upper-level ridge slowly begins to move back over North- central, Central, and Southwestern Montana. Fog will develop in the Bozeman-Belgrade area this morning due to clear skies and light winds. The ridge remains over the area on Friday. There will be a strong surface pressure gradient over North-central and Central Montana tonight through Friday which will lead to strong winds tonight along the Rocky Mountain Front which will spread to the rest of North-central and Central Montana on Friday. Due to the winds temperatures will warm up to well-above seasonal averages on Friday. Friday evening into Saturday morning a surface cold front associated with an upper-level trough begins to move through the area. The upper-level trough will remain over North-central, Central, and Southwestern Montana through Monday. This will bring cooler temperatures and mostly mountain and mountain adjacent snow with the highest amounts in northerly upslope areas Friday evening through Monday morning. An upper-level ridge moves over North-central, Central, and Southwestern Montana on Tuesday and will stay over the area through next Thursday. This will warm temperatures back up to well-above seasonal averages by the middle of next week with dry conditions. - Forecast Confidence & Scenarios: There is a 60% chance for patchy dense fog to form in the Bozeman- Belgrade area this morning. Due to low-confidence in clouds clearing early this morning to allow fog to form, at this time a Dense Fog Advisory will not be issued. There is a 20% chance for fog to form in the Helena valley this morning. Due to the low confidence a Dense Fog Advisory will not be issued. Thursday evening there is a 50% chance for winds of 55 mph or greater along the Rocky Mountain Front. On Friday there is a 75 - 95% chance for wind gusts of greater than 75 mph along the Rocky Mountain Front. On Friday there is a 50 - 70% chance for winds of 55 mph or greater along the plains adjacent to the Rocky Mountain Front. As a result a High Wind Watch was issued for the Rocky Mountain Front and adjacent plains from this evening through Friday night. Across portions of the Montana Highway 200 Corridor, Bears Paw Mountains, and Sweet Grass Hills there is a 50 - 80% chance for winds of 55 mph or greater on Friday. As a result of low confidence in widespread high winds in these areas a High Wind Watch was not issued at this time. On Saturday there is a 50 - 80% chance for winds of 55 mph or greater in the Sweet Grass Hills, Bears Paw Mountains, and portions of Fergus County. For snow on Saturday there is a 50 - 80% chance for 8 inches of snow or greater in the Little Belts. On Saturday across most lower- elevation locations there is a 10 - 40% chance for an inch of snow or greater. On Saturday there is a 40 - 70% chance for 4 inches of snow or greater between Belt and Stanford along the Montana Highway 200 Corridor. On Saturday in the Bears Paws Mountains there is a 50% chance for 6 inches of snow or greater. As a result of this being a northwest flow event and probabilities not fully matching up with what can be expected meteorologically, a Winter Storm Watch was issued from 11 PM Friday to 5 PM Saturday for the Highway 200 Corridor. In addition Winter Storm Watches remain in effect for the Little Belt, Highwood, Little Snowy, Judith, and Bears Paw Mountains. On Sunday there is a 50 - 80% chance for 8 inches of snow or greater in the Little Belts and Little Snowies. On Sunday there is a 60 - 80% chance for 4 inches of snow or greater across most of the Highway 200 Corridor east of Great Falls and in the Bears Paw Mountains. Across most of the rest of Central Montana on Sunday there is a 30 - 70% chance for an inch of snow or greater. On Monday in the Little Belts, Highwoods, and Little Snowies there is a 40 - 70% chance for 2 inches of snow or greater. On Monday there is a 30 - 70% chance for an inch of snow or greater along the Montana Highway 200 Corridor. -IG && .AVIATION... 09/12Z TAF Period Low stratus and light snow will continue to thin out in a north to south fashion as the morning progresses; however, the partial clearing will introduce patchy fog development potential. KBZN, KHLN, and KLWT look to be most susceptible to IFR/LIFR fog (30 to 60%) through 09/18Z. Probabilities drop off this afternoon, but the low January sun angle will be slow to burn the fog off should it become widespread at KBZN or KHLN. Otherwise, expect a shift to VFR conditions with increasing winds along the Rocky Mountain Front and after 10/00Z. Mountain obscuration will generally decrease today, except along the Montana/IDaho/Wyoming borders. - RCG Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PRELIMINARY POINT TEMPS/POPS... GTF 34 21 42 28 / 0 0 10 90 CTB 32 20 39 24 / 0 0 10 80 HLN 34 18 39 28 / 0 0 0 80 BZN 32 11 36 23 / 0 0 10 90 WYS 27 0 23 9 / 0 0 20 100 DLN 30 12 34 20 / 0 0 0 40 HVR 31 15 41 27 / 0 0 10 80 LWT 33 17 43 25 / 0 0 10 80 && .TFX WATCHES/WARNINGS/ADVISORIES... High Wind Watch from this afternoon through Friday evening for East Glacier Park Region-Eastern Glacier, Western Toole, and Central Pondera-Northern High Plains-Southern High Plains- Southern Rocky Mountain Front. Winter Storm Watch from Friday afternoon through Saturday afternoon for Bears Paw Mountains and Southern Blaine-Little Belt and Highwood Mountains-Snowy and Judith Mountains. Winter Weather Advisory until 5 AM MST early this morning for Big Belt, Bridger and Castle Mountains-Gallatin and Madison County Mountains and Centennial Mountains. Winter Storm Watch from Friday evening through Saturday afternoon for Cascade County below 5000ft-Fergus County below 4500ft-Judith Basin County and Judith Gap. && $$ http://www.weather.gov/greatfalls