textproduct: Great Falls

KEY MESSAGES

- It will be dry today.

- Thunderstorms return Friday through this weekend with breezy conditions Saturday evening through Sunday. - It will warm up through Saturday and then cool back down to slightly below seasonal averages early next week.

DISCUSSION

/Issued 144 AM MDT Thu Aug 20 2026/

- Meteorological Overview:

Today there is an upper-level ridge over North-central, Central, and Southwestern Montana. This will keep warm and dry conditions for the area on Thursday. Today and Thursday upper-level shortwaves will move through the upper-level flow and keep temperatures slightly cooler and bring breezy conditions to North-central, Central, and Southwestern Montana. On Friday the upper-level ridge is over North- central, Central, and Southwestern Montana. This will bring hot and mostly dry weather to the area. An upper-level shortwave will move through the upper-level flow and bring breezy conditions and an increase in monsoonal moisture to North-central, Central, and Southwestern Montana. Due to the increase in monsoonal moisture Friday afternoon and evening there will be isolated showers and thunderstorms in Southwestern Montana.

On Saturday an upper-level trough begins to move over North-central, Central, and Southwestern Montana. Due to southwest flow aloft monsoonal moisture remains over Montana on Saturday. This will bring showers and thunderstorms back to the area. Due to modestly strong low-level and mid-level winds it will be breezy on Saturday evening. On Sunday the upper-level trough is over North- central, Central, and Southwestern Montana. This will cool down temperatures slightly and due to the monsoonal moisture bring another round of showers and thunderstorms to the area. On Sunday due to modestly strong low and mid-level winds it will be breezy across North-central, Central, and Southwestern Montana. On Monday there will be upper-level zonal flow over North-central, Central, and Southwestern Montana. This will slightly cool down temperatures and bring mostly dry weather to the area on Monday. On Tuesday and Wednesday an upper-level ridge is over North- central, Central, and Southwestern Montana. This will allow temperatures to warm up on Tuesday and Wednesday. On Wednesday an upper-level trough also begins to approach Montana. This will bring a return of showers and thunderstorms to the area on Wednesday. -IG

- Forecast Confidence & Scenarios:

On Saturday there is a 25 - 35% chance for thunderstorms in Southwestern Montana. On Saturday there is a 10 - 25% chance for thunderstorms across North-central and Central Montana. On Sunday there is a 30 - 40% chance for thunderstorms across Central and Southwestern Montana. On Sunday there is a 15 - 30% chance for thunderstorms across North-central Montana. Saturday through Sunday there is a 30 - 50% chance for a quarter inch of rain or greater across the mountains of Southwestern Montana. Precipitable Water (PWAT) will increase this weekend which has the potential to lead to localized flash flooding on burn scars with the stronger thunderstorms.

On Saturday there is greater than a 50% chance for wind gusts of 25 mph or greater across North-central, Central, and Southwestern Montana. On Saturday in northern Blaine County there is greater than a 60% chance for wind gusts of 40 mph or greater. On Sunday there is a 60 - 80% chance for wind gusts of 30 mph or greater across most of North-central, Central, and Southwestern Montana. On Sunday there is a 60% chance for wind gusts of 40 mph or greater along the Rocky Mountain Front. On Sunday afternoon across North-central Montana there is a 10 - 30% chance for wind speeds of 15 mph or greater combined with relative humidity of 20% or less (red flag criteria). On Sunday there is low confidence in relative humidity reaching critical levels and so at this time it appears on Sunday there will be at least elevated fire weather concerns due to gusty winds. -IG

AVIATION

20/12Z TAF Period

VFR conditions will prevail at all terminals during this TAF Period with primarily light and variable winds. During this TAF Period smoke from wildfires will reduce slantwise visibility across North-central Montana. -IG

For KGTF: Winds will be light and variable until around 20Z. Between 20Z and 01Z westerly to northwesterly winds will gust to 15kts. There is a 65% chance for a 15kt crosswind between 21Z and 01Z.

PRELIMINARY POINT TEMPS/POPS

GTF 91 57 87 58 / 0 0 0 0 CTB 85 52 81 54 / 0 0 0 0 HLN 92 58 91 60 / 0 0 0 10 BZN 90 54 91 55 / 0 0 0 10 WYS 85 45 88 47 / 0 0 0 10 DLN 88 53 89 55 / 0 0 0 20 HVR 91 55 89 58 / 0 0 0 0 LWT 88 55 85 56 / 0 0 0 0

TFX WATCHES/WARNINGS/ADVISORIES

None.