textproduct: Great Falls

KEY MESSAGES

- There will be isolated showers and thunderstorms in Southwestern Montana this afternoon and evening.

- It will be windy on Tuesday across North-central Montana.

- Today through Friday it will warm up to around seasonal averages with mostly dry weather.

DISCUSSION

/Issued 528 PM MDT Mon Sep 28 2026/

- Meteorological Overview:

This afternoon a weak upper-level trough moves over North-central, Central, and Southwestern Montana. This will bring showers and thunderstorms to Southwestern Montana this afternoon and evening. It will warm up across the area with mostly dry weather north of I-90 this afternoon. On Tuesday there will be zonal (west to east) flow over North-central, Central, and Southwestern Montana. This will allow warm temperatures to remain with dry weather. On Tuesday there will be strong low-level and mid-level winds. This will bring windy conditions to North-central Montana with the strongest winds along the Rocky Mountain Front. On Tuesday there will be light rain and snow showers over the northern Rocky Mountain Front.

On Wednesday and Thursday zonal flow remains over North-central, Central, and Southwestern Montana with strong low-level and mid- level winds. This will bring warm and mostly dry weather to the area with breezy conditons across North-central Montana on Wednesday and Thursday. On Friday an upper-level ridge builds briefly in over North-central, Central, and Southwestern Montana. This will allow temperatures to warm up with mostly dry weather across the area. Friday afternoon/evening an upper-level trough will briefly move over North-central, Central, and Southwestern Montana. On Saturday and Sunday an upper-level ridge will build back in over North-central, Central, and Southwestern Montana. After a cool day on Saturday due to the upper-level trough Friday evening temperatures will rebound on Sunday. It will be mostly dry this weekend. -IG

- Forecast Confidence & Scenarios:

This afternoon there is a 20 - 35% chance for thunderstorms across southern Gallatin and Madison Counties. This afternoon there is a 40 - 70% chance for a tenth of an inch of rain or greater in the West Yellowstone area. On Tuesday across the Northern Rocky Mountain Front there is a 60 - 80% chance for wind gusts of 75 mph or greater. On Tuesday across the plains west of I-15 there is a 40 - 70% chance for wind gusts of 55 mph or greater. As a result a High Wind Warning was issued for the northern Rocky Mountain Front and plains west of I-15 from 12 AM Tuesday to noon on Tuesday. -IG

AVIATION

29/06Z TAF Period.

For KWYS, there is relatively good agreement in the hi-res models for fog developing overnight into the early morning hours. Right now the window of highest confidence is between 29/11Z and 29/15Z, however, fog could start forming in the valley as early as 29/14Z and persist as long as 29/17Z. If fog does develop, LIFR conditions are expected with periods of VLIFR possible until the fog begins to dissipate.

Across Central and North-Central Montana, winds will continue to gradually increase through the overnight hours, first along the Rocky Mountain Front and then across the northern plains. Mountain wave activity is possible along the Rocky Mountain Front with gusts exceeding 50kts at times. Across the plains, gusts up to 40kts are possible for KGTF and KHVR with gusts up to 30kts at KLWT. The strongest winds are expected to start tapering off after 30/00Z, however gusty conditions will continue through the remainder of the period into the evening hours on Tuesday. Periods of LLWS are possible between 29/09Z and 29/14Z as winds aloft increase first before mixing down to the surface. -thor

PRELIMINARY POINT TEMPS/POPS

GTF 47 73 52 67 / 0 10 0 10 CTB 44 66 43 58 / 0 20 0 20 HLN 41 74 47 71 / 0 10 0 0 BZN 38 72 42 70 / 0 0 0 0 WYS 27 65 28 67 / 30 0 0 0 DLN 37 72 40 71 / 0 0 0 0 HVR 43 75 46 65 / 0 10 10 10 LWT 43 75 47 66 / 0 10 0 0

TFX WATCHES/WARNINGS/ADVISORIES

High Wind Warning until noon MDT Tuesday for East Glacier Park Region-Eastern Glacier, Western Toole, and Central Pondera- Northern High Plains.