203 FXUS65 KGGW 230812 AFDGGWArea Forecast Discussion National Weather Service Glasgow MT 212 AM MDT Tue Sep 23 2025
.DISCUSSION... KEY MESSAGES:
- Several days of dry weather is expected.
- Warmer temperatures are expected today and Wednesday followed by somewhat cooler temperatures Thursday and Friday.
- South winds on Wednesday may reach Lake Wind Advisory criteria.
WEATHER PATTERN OVERVIEW:
An upper ridge over the Pacific NW will expand into Montana today and Wednesday. This will bring dry weather with warmer temperatures today and Wednesday. The upper upper trough that was over Montana on Monday moved to the south overnight. This trough will be over Colorado today and form the eastern low on a quasi omega block with another low off the southern California coast. The northern end of the upper ridge will be along the US/Canada border with fast zonal flow just to the north of the ridge over Canada. Southerly winds will increase over the area on Wednesday with very warm temperatures for late September which will be in the 80s in most areas. There is about a 10 percent chance at this point that the winds will be strong enough for a Lake Wind Advisory on Wednesday.
A wave on this zonal flow aloft will flatten the ridge enough Wednesday night to allow a weak cold front through the forecast area with somewhat cooler temperatures on Thursday. An dry upper trough on Friday will cool temperatures a few more degrees.
The ridge returns over the weekend with warmer temperatures. FORECAST CONFIDENCE & DEVIATIONS: Very high confidence on the dry weather for several days and the very warm temperatures on Wednesday.
Low confidence on the speed of the southerly winds on Wednesday and whether they will be strong enough for a Lake Wind Advisory.
No deviations from the NBM at this time.
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.AVIATION... UPDATE: 0815Z, September 23
FLIGHT CAT RANGE: VFR
DISCUSSION: Mostly clear skies will be over the region today and tonight with a few daytime cumulus this afternoon.
WIND: Light and variable winds most of the time today and tonight except for KGGW which will have south winds 5 to 10 knots this afternoon and SE winds 5 to 10 knots tonight.
EQUIPMENT: KSDY AMD NOT SKED will remain in place until METARs comms issue is repaired.
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.GGW WATCHES/WARNINGS/ADVISORIES... None. &&
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NWS GGW Office Area Forecast Discussion