textproduct: Great Falls

KEY MESSAGES

- It will gradually warm up through the end of the work week.

- Showers and thunderstorms will linger through early next week with Monday and Tuesday having the most widespread showers and thunderstorms.

- Thunderstorms will return next weekend with breezy conditions.

DISCUSSION

/Issued 112 AM MDT Sun Aug 16 2026/

- Meteorological Overview:

Today an upper-level ridge with southwest flow aloft is over North- central, Central, and Southwestern Montana. This will allow temperatures to warm up a few more degrees to be around seasonal averages. An upper-level shortwave will move through the flow and bring isolated showers and thunderstorms to North-central, Central, and Southwestern Montana this afternoon/evening. On Monday the upper- level ridge with southwest flow aloft remains over North-central, Central, and Southwestern Montana. By Monday evening the upper-level ridge begins to break down and an upper-level trough begins to move over the area. This will bring breezy conditions to the area with showers and thunderstorms Monday afternoon and evening. Temperatures will remain near seasonal averages on Monday.

On Tuesday there will be zonal flow (west - east) over North- central, Central, and Southwestern. This will allow temperatures to remain near seasonal averages with breezy conditions. There will also be showers and thunderstorms across North-central, Central, and Southwestern Montana on Tuesday. On Wednesday and Thursday an upper-level ridge begins to build back in across North-central, Central, and Southwestern Montana. On Wednesday and Thursday temperatures will remain around seasonal averages. On Wednesday and Thursday it will be mostly dry across the area. On Friday the upper-level ridge is over North-central, Central, and Southwestern Montana. This will bring hot and dry weather to the area. On Saturday an upper-level trough begins to move over North-central, Central, and Southwestern Montana. This will bring showers and thunderstorms back to the area. Due to strong low-level and mid- level winds it will be breezy on Saturday. -IG

- Forecast Confidence & Scenarios:

This morning in any areas that clear fog has a high chance to form. The areas that have the greatest risk for fog forming this morning are the valleys of Southwestern Montana and along the river valleys of North-central Montana. On Sunday there is a 20 - 35% chance for thunderstorms across North-central, Central, and Southwestern Montana.

Monday afternoon/evening into Tuesday the track and timing of the upper-level ridge breakdown/upper-level trough moving through the area will affect the strength of thunderstorms Monday afternoon through Tuesday. On Monday there is a 15 - 25% chance for thunderstorms across North-central and Central Montana. On Monday there is a 25 - 35% chance for thunderstorms in Southwestern Montana. On Tuesday there is a 30 - 40% chance for thunderstorms across Central and Southwestern Montana. On Tuesday there is a 15 - 25% chance for thunderstorms across North-central Montana. -IG

AVIATION

16/12Z TAF Period

VFR conditions will prevail across all terminals during this TAF Period outside of during any thunderstorms. Between 16/18Z and 17/06Z isolated showers and thunderstorms will affect all of the terminals. All thunderstorms will produce frequent lightning, a brief heavy downpour, and gusty, erratic winds. During any thunderstorms there will be a brief period of mountain obscuration. -IG

For KGTF: There will be light winds during this TAF Period with a very low chance for exceeding a 15 kt crosswind. However there is around a 20% chance for thunderstorms to affect KGTF between 16/21Z and 17/03Z. The primary risks from any thunderstorms will be gusty, erratic winds up to 35 kts and lightning. -IG

PRELIMINARY POINT TEMPS/POPS

GTF 83 52 81 52 / 40 40 10 20 CTB 75 47 74 47 / 20 20 10 20 HLN 82 51 81 55 / 30 40 10 10 BZN 80 48 80 50 / 40 50 10 40 WYS 75 36 76 39 / 30 30 20 40 DLN 77 46 79 49 / 40 40 10 40 HVR 84 51 81 50 / 30 30 30 20 LWT 79 50 77 49 / 30 30 20 30

TFX WATCHES/WARNINGS/ADVISORIES

None.