Area Forecast Discussion
Issued by NWS Glasgow, MT
Issued by NWS Glasgow, MT
639 FXUS65 KGGW 060620 AFDGGW Area Forecast Discussion National Weather Service Glasgow MT 1220 AM MDT Sun Sep 6 2026 .KEY MESSAGES... - Shower and thunderstorm chances at times today with a risk of a severe thunderstorm. - Widespread rain is expected tonight through Monday night as the upper low moves through Montana. - Strong west winds develop Monday afternoon and continue through Tuesday. && .DISCUSSION... WEATHER PATTERN OVERVIEW: Montana will be in SW flow aloft today with upper low over the Pacific NW and upper ridge to the east. A humid airmass will combine with the moist SW flow aloft today to create an unstable atmosphere which will allow for chances for showers and thunderstorms at times. A few storms could become severe with large hail and damaging winds. It looks like the Yellowstone Valley and points east will have another hot day with highs in the 90s. Surface low develops over SE Montana this afternoon and tonight. Meanwhile, a wave on SW flow aloft tonight will allow widespread rain with scattered thunderstorms to develop with heavy rain possible at times. The upper low moves into Montana on Monday as the surface low moves north into Saskatchewan. Rain is expected to continue most of the time in the north while the models differ on how much the dry slot will limit rain in the south. The upper low moves to Saskatchewan and Manitoba Monday night and becomes stacked with the surface low. Gusty west winds will develop during the day on Monday and continue Monday night and Tuesday with gusts to 40 to 50 mph possible. A Lake Wind Advisory will most definitely be needed for Monday night into Tuesday. Wrap around rain is likely Monday night and Tuesday over the NW half of the forecast area while the SE will be dry most of the time. Rainfall totals 1 to 2 inches are likely in the NW between tonight and Tuesday while some areas in the SE could end up with less than a tenth of an inch. The system exits the region Tuesday night and Wednesday and Thursday are expected to be dry. FORECAST CONFIDENCE & DEVIATIONS: There is moderate to high (50 to 80 percent) confidence in rain amounts from tonight through Tuesday, and winds for Monday afternoon through Tuesday. There is low confidence in the showers and thunderstorm chances today. Tweaked pops at times tonight to provide better hour to hour consistency. && .AVIATION... LAST UPDATED: 0630Z FLIGHT CAT RANGE: VFR most of the time with areas of IFR/MVFR DISCUSSION: There will be varying amounts of low and mid level clouds today and tonight. CIGS will be VFR most of the time but areas of MVFR/IFR CIGS are possible this morning and again tonight. Southwest flow aloft will help bring in some upper level moisture, so there will be shower and thunderstorm chances at times today and this evening. Widespread rain with scattered thunderstorms will develop late tonight and continue on Monday. WINDS: North to northeast at 5 to 15 knots today becoming east to NE tonight. && .GGW WATCHES/WARNINGS/ADVISORIES... None. && $$ weather.gov/glasgow