FXUS65 KBYZ 012101 AFDBYZ Area Forecast Discussion...Updated National Weather Service Billings MT 201 PM MST Sun Nov 1 2026 .KEY MESSAGES... - Patches of dense fog continue early this afternoon for portions of south-central Montana. Prepare for significant reductions to visibility. - Widespread precipitation expected this afternoon through Monday. Well above normal precipitation amounts forecast for southeast Montana. - Moderate to heavy snowfall expected for north and west aspects of the Absaroka/Beartooth and Bighorn Mountains through Monday. Very difficult conditions expected in the back country as well as travel through the Bighorns. - Windy conditions on Monday, gusts 25 to 45 mph. A few gusts of 50 mph or higher in Southeast Montana and Northern Wyoming. && .DISCUSSION... Rest of Today through Saturday... While widespread dense fog has largely ended, current observations and model trends show patches of dense fog continuing into this afternoon. Areas impacted include Stillwater, Yellowstone, Musselshell, Treasure, Bighorn, and portions of Carbon County. As a result, the Dense Fog Advisory has been extended until 2 PM this afternoon for reductions to visibility to a quarter mile or less. Please use caution when traveling. An upper trough is beginning to impact the Northern Rockies as it progresses through the Mountain West into the new week. This system will bring an abundance of atmospheric moisture to the region, with precipitable water anomalies of nearly 300% over southeast Montana into Monday. The liquid precipitation forecast is shown as an extreme event for this time of year, with the ECMWF EFI (Extreme Forecast Index) displaying values of 0.8 to 1.0 (with 1 being the maximum). Values of 0.8 or greater signify an extreme or very unusual event. More on this shortly. Showers have begun to develop over south-central Montana and will continue to spread across the entire forecast area through this afternoon and last into Monday. Widespread rainfall is expected, while snowfall will occur in the mountains. Moderate to heavy rainfall is expected south and east of Billings where there 0.75 to 1.5 inches of rainfall is forecast. The latest probability for greater than 1 inch of rainfall is 60 to 90% for portions of Big Horn and Treasure Counties and all counties to the east. The probability for at least 2 inches of rainfall for the same area is 10 to 30%. For portions of northern Wyoming, rainfall up to or greater than an inch are possible although confidence is lower. This is partly do to a developing surface low in southern Wyoming that may result in some drier periods over the next 24 hours. The probability for at least a half inch remains high (60 to 85%) though. For the rest of south-central Montana several tenths of an inch of rainfall are in the forecast, though amounts are lower going north and west of Billings. The probability for at least half an inch of rain is 40 to 90% (greatest around Billings and the Absaroka/Beartooth foothills). Circling back to the EFI discussion, the single day precipitation record for the Miles City Airport in November is 1.17" on November 1st of 1957. For the upcoming event, the forecast has 1 to 1.4 inches of rainfall in the Miles City area. It does not appear as though KMLS will set a new single day record, as several tenths of an inch of rain are forecast for this evening splitting the storm total across the first two days of the month. While a single day record for KMLS looks unlikely, the average precipitation total for the month of November at KMLS from 1990 to 2020 was 0.33". Across the entire period of record for KMLS (records began in 1937), the average for November is 0.42". In other words, this is going to be a very wet month after just 2 days. ForSheridan, the single day November precipitation record occurred on November 9th, 1978 when 0.85" of precipitation fell. For this event around 3/4 of an inch are forecast for Monday. A single day record could be broken. For the month overall, the average from 1990 to 2020 was 0.76". The period of record goes back to 1907 and the average since then is 0.78". KSHR may surpass the monthly average after two days as well. In the mountains, snowfall will begin tonight and last through Monday afternoon. North and west aspects of the Absaroka/Beartooths and the Bighorns will be favored. This system will not bring much cold air with it, although snow levels drop as low as 5,500 feet Monday morning. A rain/snow mix will start in the high country before transitioning to all snow tonight. For the Absaroka/Beartooths, 4 to 8 inches of snowfall are forecast though locally higher amounts are possible. In the Pryors, up to 4 inches are forecast. For the Bighorns, 5 to 10 inches are forecast with locally higher amounts possible. The majority of accumulations in the Absaroka/Beartooth and Bighorn Mountains will fall above 7,500 feet. With snow levels as low as 5,500 feet, foothill locations such as Red Lodge could see some light snowfall as well although accumulations will be minimal (less than an inch). A cold front is expected to move across the area tonight into Monday, this will bring widespread breezy north-northwest winds with gusts in the 20s to 40 mph. Windier conditions are forecast for southeast Montana and northern Wyoming with gusts in the 40s to low 50s mph. The probability for gusts of 50 mph or greater in Sheridan County is 40 to 90%, greatest along the Johnson County line. The probability for gusts greater than 60 mph in Sheridan County is around 20 to 40%, almost exclusively along the Johnson County line. For locations in southeast Montana, the probability for 50 mph is 40 to 80% along and east of State Highway 323 and greatest along the border. The probability for 60 mph winds is 20% or less. The combination of snowfall and windy conditions in the Bighorns will result in very difficult conditions for those traveling along Highway 14, as well as those in the back country. Because of this, a Winter Weather Advisory is in effect until 8 PM MST Monday with up to 11 inches of snowfall and winds gusting to 50 mph. Please be prepared if you have plans in the Absaroka/Beartooth, Pryor, and Bighorn mountains during this time. Ridging is shown rebuilding Tuesday through midweek, with warmer seasonable temperatures (50sF) and mostly dry conditions. An occasional disturbance in the flow pattern may bring an isolated shower or two into the mountains. Matos .AVIATION... Persistent fog and low are continuing to bring areas of IFR/LIFR conditions into early afternoon. There may be a period of local VFR briefly at some sites in the west (ie KLVM, KBIL) around midday. Then, as precipitation becomes more widespread this afternoon, MVFR/IFR conditions will be common. Mountains will be obscured through the period. Expect occasional local reductions to LIFR tonight into Monday morning, especially near KMLS. Precipitation will begin to end from west to east late Monday morning. Winds become breezy out of the northwest late this evening into Monday morning, with widespread gusts of 25 to 40 kts. Archer && .PRELIMINARY POINT TEMP/POPS... Tdy Mon Tue Wed Thu Fri Sat ------------------------------------------------------- BIL 047 040/047 032/055 034/052 033/056 035/057 036/054 9/W +9/W 10/B 00/B 00/B 00/B 20/U LVM 047 032/045 024/055 030/052 027/054 028/053 028/052 8/W +7/W 00/B 00/B 00/U 11/B 30/U HDN 052 036/047 027/057 027/054 027/057 029/059 033/056 7/W ++/W 10/B 00/B 00/B00/B 31/U MLS 054 041/046 030/052 030/052 030/054 031/055 035/053 7/W ++/W 10/U 00/B 00/B 00/U 11/B 4BQ 058 041/044 029/053 030/052 030/055 032/056 036/053 7/W ++/W 50/U 00/B 00/B 00/U 21/B BHK 058 040/050 028/050 026/053 026/053 029/055 030/051 3/W ++/W 40/B 00/U 00/B 00/B 11/B SHR 051 031/044 025/057 027/054 026/057 028/058 030/055 5/W ++/W 30/U 00/B 00/U 01/U 31/N && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...Winter Weather Advisory in effect from 11 PM this evening to 8 PM MST Monday FOR ZONE 171. WY...Winter Weather Advisory in effect from 11 PM this evening to 8 PM MST Monday FOR ZONE 198. && $$ weather.gov/billings