textproduct: Great Falls

KEY MESSAGES

- Above average temperatures this week.

- Dry conditions aside from a stray shower or thunderstorm Tuesday afternoon and Wednesday.

- Next system arrives late week with windy and wet conditions.

UPDATE

Updated forecast is out. Just minor adjustments towards current trends. Some fog still possible by morning along the Highway 2 corridor from Cut Bank to Harlem and in the West Yellowstone area. Otherwise, should be a quiet night. Thunderstorms return tomorrow afternoon/evening over Southwest and Central MT. Brusda

DISCUSSION

/Issued 200 PM MDT Mon Sep 21 2026/

- Meteorological Overview:

Southwesterly upper level flow will be the predominant weather pattern this week as upper level ridging stalls out over the center of the North American Continent this week, keeping us generally warm and dry for most of this week. Expect temperatures to generally be either side of 80 along the Missouri River corridor, with temperatures not as warm in the higher terrain and along the Rocky Mountain Front. Winds will also be uncharacteristically light for much of the week, with winds generally struggling to gust over 20 mph through Thursday. Aside from a stray shower or thunderstorm across Southwestern Montana Tuesday or Wednesday afternoon, our next weather system will arrive Friday or Saturday, which will bring cooler temperatures, gusty winds, and the possibility for some widespread precipitation, though the amount of rainfall remains fairly uncertain at this point in time.

- Forecast Confidence & Scenarios:

Friday/Saturday system: an upper level trough and associated surface front embedded in the upper level flow are expected to arrive in the Northern Rockies late Friday. Current model forecasts suggest that this setup will bring some widespread precipitation, with the potential for many areas to receive over a quarter inch of liquid equivalent. The other concern will be the wind, as the strengthening trough may produce a bit of a descending jet on its southwest side, which would produce some gusty westerly winds thanks to the sinking air behind a cold front. As of Monday afternoon, probabilities for 60 mph wind gusts still appear low (generally under 20 percent). However, wind gusts over 50 mph are likely to be common, and stronger wind gusts will be heavily dependent on the timing and strength of this system. Ludwig

AVIATION

22/00Z TAF Period

Quiet and dry conditions are expected overnight, expect for some fog that could develop, mostly around Havre and West Yellowstone. LIFR conditions are possible in dense fog at times around 12z. There is a chance for showers/thunderstorms, mostly after 21z Tue over Southwest MT. These showers/thunderstorms will spread northward towards Central MT by 00z Wed. Mountains/passes could be obscured at times Tue afternoon by showers/thunderstorms. Brusda

PRELIMINARY POINT TEMPS/POPS

GTF 49 80 50 80 / 0 0 0 0 CTB 45 77 48 73 / 0 0 0 0 HLN 46 78 48 78 / 0 0 20 0 BZN 41 75 45 75 / 0 0 20 0 WYS 30 66 33 65 / 0 0 50 0 DLN 41 73 42 74 / 0 10 20 0 HVR 46 80 49 81 / 0 0 0 0 LWT 45 79 49 78 / 0 0 10 0

TFX WATCHES/WARNINGS/ADVISORIES

None.