Area Forecast Discussion
Issued by NWS Glasgow, MT
Issued by NWS Glasgow, MT
594 FXUS65 KGGW 132058 AFDGGW Area Forecast Discussion National Weather Service Glasgow MT 258 PM MDT Sun Sep 13 2026 .KEY MESSAGES... - Likely scattered rain showers and embedded thunderstorms beginning around midnight and lasting through tomorrow evening. - Winds will reach Lake Wind Advisory Criteria today and tomorrow. Wave heights will have the potential to reach 4 to 5 ft tomorrow afternoon. - Slight chances for rain showers are possible Tuesday night into Wednesday morning. Confidence in rain amounts is low. && .DISCUSSION... Synoptic Setup: A weak ridge is over the western Great Plains and a closed upper- level low has moved over the Pacific Northwest. The interaction of these two systems has produced SW flow aloft over Montana, transporting Pacific moisture into the region. Today Through Tomorrow: While the stability in the upper atmosphere will keep conditions dry into early this evening, the aforementioned PNW low will weaken and dig over Montana tonight. This will likely produce scattered rain showers and embedded thunderstorms beginning around midnight and lasting through tomorrow afternoon. A cold front associated with the trough will likely pass between midnight and 6AM, producing precipitation totals between 0.01" and 0.50". Additionally, vorticity-indudced instability associated with the backside of the low may result in rain showers lasting into early Monday evening across northern portions of the CWA. Confidence in precipitation amounts associated with later afternoon and evening showers is low, but expect higher totals north of a line drawn between Malta and Terry. Winds will veer and become westerly behind the front Monday morning and be comparable in strength to winds experienced today. Winds will reach Lake Wind Advisory Criteria tomorrow. Wave heights will have the potential to reach 4 to 5 ft tomorrow afternoon. Tuesday Onward: The trough will fully exit the region by Tuesday morning, leaving zonal flow in its wake. Slight chances for rain showers are possible Tuesday night into Wednesday morning due to a swath of Pacific moisture moving throughout the flow. Confidence in rain amounts is low, but best chances will be across northern portions of the CWA. Rain chances fully diminish by Wednesday afternoon as skies clear and temperatures warm under a developing ridge over the Central US. Although, a weak trough has embedded itself between us and the ridge in a significant portion of the ensembles, which could potentially produce rain and increasing cloud coverage Friday night. FORECAST CONFIDENCE & DEVIATIONS: There is HIGH confidence in sustained winds at or above 20 mph on today and tomorrow across Fort Peck Lake. There is MODERATE confidence in the timing of scattered showers and thunderstorms on tonight into Monday (They could begin earlier or later), but there HIGH confidence in them lasting into the evenings hours. There is LOW confidence in the forecast beyond Thursday. DON && .AVIATION... LAST UPDATED: 2100Z FLIGHT CAT RANGE: VFR DISCUSSION: Mid-level clouds will slowly drop in height this evening and through tonight as a disturbance and associated front approaches. This disturbance will bring scattered rain showers and thunderstorms to terminals tomorrow morning. SFC WIND: SE and increasing to 10 to 20 gust 30 kts this afternoon and evening. Winds will veer rapidly to W to NW after after the passage of a cold front around midnight. DON && .GGW WATCHES/WARNINGS/ADVISORIES... Lake Wind Advisory until midnight MDT Monday night for Central and Southeast Phillips-Central and Southern Valley-Garfield- McCone-Petroleum. && $$ weather.gov/glasgow