Area Forecast Discussion
Issued by NWS Glasgow, MT
Issued by NWS Glasgow, MT
808 FXUS65 KGGW 130648 AFDGGW Area Forecast Discussion National Weather Service Glasgow MT 1248 AM MDT Sun Sep 13 2026 .KEY MESSAGES... - Rain will be likely across northeast portions of Montana this evening through Monday afternoon. Precipitation totals will range between 0.01" and 0.25". - A Lake Wind Advisory has been issued due to SE wind being expected to reach 20 to 25 mph sustained this afternoon. Wave heights have the potential to reach 3 ft. - SW Winds will likely reach Lake Wind Advisory criteria again Monday afternoon. Wave heights have the potential to reach 4.5 ft. && .DISCUSSION... Synoptic Setup: Forecast begins with a weak ridge poking up from Colorado through Wyoming and into eastern Montana. Far to the West a closed low has begun moving onto the shore of the Pacific Northwest. In between these two airmasses SW flow has set up in between pulling in pacific moisture from off the coast of northern California into Idaho and western Montana. Today through this evening: Ridge exiting to the west will keep conditions stable through most of the day and therefore dry. However as the closed low to the west moves inland over the PCNW a surface pressure gradient will form creating a strong wind that will easily lead to a Lake Wind Advisory this afternoon. Monday morning to evening: While the stability in the upper atmosphere will keep conditions dry into the early evening. The exit of the trough and entrance of SW flow will allow enough instability and pacific moisture to strike off some scattered rain showers and embedded thunderstorms around midnight lasting through Monday afternoon. Cold front associated with the trough will likely pass across the area from midnight to 6AM and produce precipitation totals ranging between 0.01" and 0.25". The front itself has backed up 6 to 12 hours from the previous forecast so their is lower confidence in the timing of the passage and associated showers. Wind will veer westerly behind the front Monday morning. This will of comparable in strength to today in reaching advisory criteria. Wave heights have the potential to reach 4.5 ft, particularly Monday afternoon. Tuesday onward: The trough will fully exit the region Tuesday morning with the zonal flow left in its wake. Slight chances for rain showers are possible Tuesday night into Wednesday morning due to a swath of pacific moisture moving throughout. Confidence in rain amounts are low. Rain chances diminish Wednesday afternoon as skies clear and temperatures warm under a developing ridge over the PCNW Thursday. A weak trough has embedded itself between us and the ridge in a significant portion of the ensembles which is lowering confidence heavily from Thursday onward. FORECAST CONFIDENCE & DEVIATIONS: No Deviation from NBM were observed. There is HIGH confidence in sustained winds at or above 20 mph on today and Monday across Fort Peck Lake. There is MODERATE confidence timing of scattered showers and thunderstorms Monday morning,(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/GAH && .AVIATION... LAST UPDATED: 0700Z FLIGHT CAT RANGE: VFR DISCUSSION: BKN mid level clouds will likely clear out from west to east early this morning. High clouds will then enter this evening hours and slowly drop to mid levels as a disturbance and front approaches. This disturbance will bring scattered rain showers and thunderstorms to the terminals Monday morning. SFC WIND: E at 10 kts or less through the morning. Veering SE and increasing to 10 to 20 gust 30 kts in the afternoon and evening. Veering rapidly W to NW after after the passage of a cold front around midnight. DON/GAH && .GGW WATCHES/WARNINGS/ADVISORIES... Lake Wind Advisory from 10 AM this morning to midnight MDT tonight for Central and Southeast Phillips-Central and Southern Valley-Garfield-McCone-Petroleum. && $$ weather.gov/glasgow