FXUS65 KBYZ 202030 AFDBYZ Area Forecast Discussion National Weather Service Billings MT 230 PM MDT Sun Sep 20 2026 .KEY MESSAGES... - Flood Watch in effect until 6 PM MDT for southeast Montana and portions of northern Wyoming today. - Patchy to areas of fog developing tonight into Monday morning. - Warmer and drier for the work week. Isolated showers linger. && .DISCUSSION... Today through Saturday... Showers continue across southeast Montana and portions of northern Wyoming as an upper low progresses through Wyoming today. Rainfall rates are not expected to be as high as the past few days, though heavier showers and a few thunderstorms this afternoon could produce locally heavy rainfall in southeast Montana and northern Wyoming. Additional rainfall up to a few tenths of an inch are forecast into Monday morning. The greatest accumulations are likely to occur along and south of US-212. Lighter showers over south- central Montana could bring a few hundredths of an inch of additional rainfall through tonight. Flood Watches remain in effect until 6 PM MDT due to the aforementioned risk of locally heavy rainfall this afternoon. The greatest risk exists mainly east of Billings. Patchy to areas of fog are shown developing by several models tonight, the forecast shows this as well. There is uncertainty on fog developing versus low stratus prevailing, mainly for locations west of Billings. Fog could become dense at times into Monday morning, especially for areas that received a lot of rainfall over the past few days. This will need to be monitored overnight as products may be required if fog becomes enough of an issue. Looking ahead, the pattern will get warmer with highs in the 70s Monday through Wednesday. Conditions also look to become drier, though a shortwave moving through Wednesday morning may bring elevated showers and maybe a few thunderstorms to southeast Montana. Otherwise, an additional upper low is shown by ensembles digging into the Pacific Northwest to end the week. This could bring more precipitation to the area as well as cooler temperatures. The latest trends have this system tracking through northern Montana which could leave our area in flux for precipitation amounts. Continue to monitor the forecast as the week progresses. Matos .AVIATION... Widespread showers will continue to impact eastern Montana and northern Wyoming today, gradually diminishing from west to east this evening into tonight. With that said, light showers may linger into Monday morning over south-eastern Montana (15 percent chance). While the chance of thunderstorms is low today, cannot rule out an embedded thunderstorm over south-eastern Montana and northern Wyoming this afternoon and early evening (20 percent chance). The main threat with any thunderstorm is heavy rain. Otherwise, humid conditions will result in areas of MVFR/IFR ceilings along with patchy fog today into tonight. Look for the low stratus or fog to increase in coverage tonight as the precipitation comes to an end. Fog may become locally dense with visibility around or below 1/4SM late tonight into early Monday morning. Any fog that does develop, along with areas of low stratus, will dissipate around 14Z to 17Z Monday. LA && .PRELIMINARY POINT TEMP/POPS... Mon Tue Wed Thu Fri Sat Sun ----------------------------------------------------------- BIL 048/072 048/077 053/078 053/082 054/082 053/070 047/066 10/B 00/U 22/W 00/U 00/U 12/W 22/W LVM 041/073 043/078 048/077 047/081 050/081 046/068 039/066 00/U 00/U 11/U 00/U 00/U 22/W 32/W HDN 045/073 044/080 050/079 047/084 050/085 049/073 043/069 22/W 00/B 32/W 00/U 00/U 11/U 12/W MLS 050/069 049/077 053/077 051/084 057/085 054/073 047/069 22/W 00/U 13/T 00/U 00/U 11/U 21/B 4BQ 050/067 049/076 053/077 052/083 057/084 055/075 049/071 42/W 00/U 21/B 00/B 00/U 00/U 12/W BHK 044/066 043/073 047/078 048/084 052/083 051/076 044/070 32/W 00/N 15/T 10/B 00/N 00/U 22/W SHR 041/070 041/076 047/075 044/082 049/083 048/074 042/070 62/W 00/U 22/W 00/U 00/U 01/U 11/U && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...Flood Watch in effect until 6 PM MDT this evening FOR ZONES 29>33-36-37-57-58-138-169-171-173-235. WY...Flood Watch in effect until 6 PM MDT this evening FOR ZONES 198-199. && $$ weather.gov/billings