Area Forecast Discussion
Issued by NWS Glasgow, MT
Issued by NWS Glasgow, MT
660 FXUS65 KGGW 252204 AFDGGW Area Forecast Discussion National Weather Service Glasgow MT 404 PM MDT Fri Sep 25 2026 .KEY MESSAGES... - Lake Wind Advisory remains in effect until Saturday at 9 AM. - Daily high temperatures to drop into the mid to upper 60s Saturday through the outlook. - Possible rain showers between late Sunday afternoon and late Monday morning south of the Missouri River and west of Fort Peck Lake. FINDLEY && .DISCUSSION... SYNOPTIC SETUP: An upper-level ridge over the central United States and an Eastern-Pacific neutrally tilted longwave trough, west of British Columbia/Washington State over the Pacific is creating SW flow aloft over Montana. An omega blocking pattern is present over CONUS which is causing the surface low advancing towards our region to be delayed into Monday, perhaps into the evening of Monday. TONIGHT THROUGH TOMORROW: Currently, meridional setup has begun in the region as the ridge has starting exiting eastward, ushering in an upper-level disturbance to our area by this evening. This disturbance is associated with mid-to-low level perturbations which may cause some increased forcing, though forecast preciptable water content is not sufficient per current model guidance. PoPs should remain in the single digits throughout this period. An enhanced pressure gradient force (PGF) will form due to the cold frontal passage causing breezy conditions with peak gusts up to 35 mph. A Lake Wind Advisory is currently in effect until Saturday at 9AM. TOMORROW NIGHT THROUGH SUNDAY: Due to the current blocking pattern, the embedded negatively-tilted shortwave trough will continue eastward as the main trough over western Montana and the front passes by early Saturday morning. Frontal passage will cause winds to veer W/NW and high temperatures Sunday will drop into the mid to upper 60s. Post frontal passage timing remains steady. Furthermore, pressure gradient force (PGF) increases, leading to faster winds by late Saturday afternoon. SUNDAY INTO MONDAY NIGHT: The trough axis will exit to the NE, leaving SW flow aloft over Montana in it`s wake. Low-level moisture moving through this flow coupled with isolated pockets of vorticity may generate rain showers in the furthest-most southeastern counties. Thunderstorms cannot be ruled out during this time in the Yellowstone Valley. Currently, the chance of a wetting rain is possible in southeast Dawson County and to areas further east and south of that TUESDAY MORNING ONWARD: Forecast has shifted a bit since the last update. Current model guidance suggests Hurricane Polo may create a conveyor belt of moisture transport into our region, potentially elevating PoPs. FORECAST CONFIDENCE & DEVIATIONS: Surface winds in the short-term are aligning closer to baseline NBM rather than NBM 90th percentile. NBM90 was initially used last update, however, has become a tad too aggressive. The cold frontal passage timing has also deviated from today, shifting the passage into the early morning hours of Saturday due to the blocking pattern currently in place. There is still some uncertainty during this forecast update regarding possible stronger wind gusts overnight after the frontal passage throughout the early morning hours on Saturday. FINDLEY && .AVIATION... LAST UPDATED: 1800Z FLIGHT CAT RANGE: VFR DISCUSSION: High clouds this afternoon will drop to mid levels as a cold front approaches the area overnight. The approaching front will raise gusty winds with a direction switch from SE to NW on either side of it as it moves through the area around 6 to 12Z. Afterward cloud bases will rise through Saturday. LLWS: There is a small chance (10-30%) for low-level wind shear across the region from 06-15Z tonight due to a developing low- level jet for most terminals. Confidence is only high enough to include LLWS in the TAFs directly at KGDV. SFC WIND: SE at 15 to 25 kts gusting 30 kts this afternoon and evening. Turning W to NW behind a cold front around midnight and reducing to 10 to 20 kts gusting 25 kts Saturday morning through the afternoon. Further reducing to around 10 kts Saturday evening. && .GGW WATCHES/WARNINGS/ADVISORIES... Lake Wind Advisory until 9 AM MDT Saturday for Central and Southeast Phillips-Central and Southern Valley-Garfield-McCone- Petroleum. && $$ weather.gov/glasgow