textproduct: Great Falls

KEY MESSAGES

- It will warm up through Monday with a brief cooldown on Tuesday before it warms up to end the work week.

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

DISCUSSION

/Issued 154 AM MDT Sat Aug 15 2026/

- Meteorological Overview:

This morning there is upper-level zonal flow over North-central, Central, and Southwestern Montana which will build into an upper- level ridge with southwest flow aloft by this afternoon. This will keep monsoonal moisture around but allow temperatures to warm up several degrees compared to yesterday but still be slightly below seasonal averages. This afternoon and evening there will be another round of showers and thunderstorms primarily confined to Southwestern Montana. On Sunday the upper-level ridge with southwest flow aloft remains 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 Sunday 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. This will bring breezy conditions to the area with isolated 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 Montana. This will allow temperatures to cool down to below seasonal averages with breezy conditions due to modestly strong low and mid-level winds. 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 warm back up to 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. -IG

- Forecast Confidence & Scenarios:

In any areas where skies clear this morning there is a moderate chance for fog to form.

Today there is a 30% chance for showers and thunderstorms in Central and Southwestern Montana. On Sunday there is a 20 - 30% chance for thunderstorms across North-central, Central, and Southwestern Montana. On Monday there is a 15 - 30% chance for thunderstorms across North-central, Central, and Southwestern Montana. On Tuesday there is a 30 - 40% chance for thunderstorms across most of North- central, Central, and Southwestern Montana.

Today there is a 20 - 50% chance for a quarter inch of rain or greater across most of Southwestern Montana. As a result there is too low of a risk to consider any potential flash flooding on burn scars today. -IG

AVIATION

15/12Z TAF Period

VFR conditions will prevail across the KEKS and KBZN terminals during this TAF Period outside of during any thunderstorms. During the beginning of this TAF Period at the KGTF, KCTB, and KLWT terminals ceilings will be at least IFR-levels for a couple hours before gradually going to VFR-levels around 15/18Z. At the KWYS and KCTB terminals for the first couple of hours of this TAF Period fog will reduce visibility to one half mile or less and then the visibility will gradually improve. Across the KBZN, KEKS, KWYS, and KHLN terminals there will be showers and thunderstorms after 15/18Z. All thunderstorms will produce gusty, erratic winds and frequent lightning. During the first 6 hours of this TAF Period and during any thunderstorms there will be mountain obscuration across North-central, Central, and Southwestern Montana. -IG

For KGTF: There will be light winds during the duration of this TAF Period with a low risk for exceeding a 15 kt crosswind. Between 03Z and 05Z there is a 20% chance for a thunderstorm. Any thunderstorms have the potential to produce gusty, erratic winds and/or an outflow boundary which could briefly cause the 15 kt crosswind threshold to be exceeded. -IG

PRELIMINARY POINT TEMPS/POPS

GTF 77 51 83 52 / 0 20 20 20 CTB 71 46 77 47 / 0 0 10 10 HLN 78 50 82 53 / 20 50 10 20 BZN 77 47 79 48 / 20 40 10 30 WYS 72 34 75 35 / 50 50 20 10 DLN 74 44 77 46 / 50 40 10 30 HVR 76 49 84 50 / 0 0 10 20 LWT 73 48 79 49 / 30 40 30 20

TFX WATCHES/WARNINGS/ADVISORIES

None.