textproduct: Great Falls

KEY MESSAGES

- Shower and thunderstorms chances continue through Tuesday, with some of the stronger storms producing gusty outflow winds and heavy downpours.

- Temperatures near normal through much of the upcoming week.

- Gusty winds return from the middle of the work week through the upcoming weekend, which combined with dry conditions will lead to elevated fire weather conditions.

DISCUSSION

/Issued 1151 AM MDT Sun Aug 16 2026/

- Meteorological Overview:

Monsoonal moistures lifting north and east around upper level ridging centered over the Central Rockies through the Desert Southwest will support another day of scattered to numerous showers and thunderstorms across Southwest Montana, with isolated to widely scattered showers and storms over Central and North Central Montana. While showers and thunderstorms will decrease in coverage through the late evening hours tonight an isolated shower or storm can't be ruled out into the early morning hours on Monday, most notably over the plains of Central and North Central Montana where weak low level frontogenetic forcing will reside throughout the overnight hours. Partly clearing skies beyond midnight tonight combined with recent precipitation and light winds will support another opportunity for patchy fog across the Northern Rockies; most notably in the prone valleys of Central and Southwest Montana. - Moldan

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:

Showers and Thunderstorms through Tuesday...

Sufficient shear, but marginal instability, will help to support continued chances for convection through the first half of the upcoming work week as monsoonal moisture continues to lift north and east around broad ridging centered over the Central Rockies and Desert Southwest. Inverted-V soundings and and tall skinny CAPE profiles support the potential for gusty outflow winds and the potential for periods of heavy rainfall, especially across Southwest Montana.

Gusty Winds from Wednesday through next Sunday...

Increasing zonal to southwesterly flow aloft will support gusty winds, most notably during the afternoon and evening hours, from the middle to the work week through next weekend with the exception of Thursday. These gusty southwest to west surface winds will initially occur along the Rocky Mountain Front on Wednesday, with a 20-30% chance that gusts exceed 35 mph. By Friday NBM5.0 probabilities for wind gusts exceeding 35 mph expand to all areas, with probabilities increasing to between a 20-60% chance for the upcoming weekend. While 35 mph wind gusts are not unusual, let alone noteworthy during the windy season, moderating temperatures and dry conditions will lead to increasing fire weather concerns given these speeds. - Moldan

AVIATION

17/00Z TAF Period

Scattered showers and thunderstorms across the whole region are moving eastward producing brief strong, gusty winds, cloud to ground lightning, and localized moderate to heavy rain. Most convection will end by 04Z tonight then overnight there is a 40% chance for patchy fog and mist to set up again between 17/09 and 17/16Z in the KWYS area with MVFR to IFR ceilings and visibility most likely. VFR conditions are expected throughout the rest of the terminals tonight into the morning. Tomorrow afternoon will see more isolated coverage for thunderstorms mainly for the Northern and Southwestern terminals.

For KGTF: Prevailing winds tonight will be light and variable with VFR conditions. Winds will shift to the Northwest after 17/21Z at around 9 KT predominantly. Currently there is only a 10% chance for isolated showers and thunderstorms tomorrow afternoon. - Akins

PRELIMINARY POINT TEMPS/POPS

GTF 52 83 54 84 / 20 20 10 20 CTB 48 77 48 79 / 20 20 20 10 HLN 51 84 55 83 / 20 20 20 20 BZN 48 81 50 81 / 50 10 30 20 WYS 35 77 39 76 / 30 30 40 40 DLN 47 80 50 79 / 30 20 30 30 HVR 52 83 51 85 / 20 20 20 10 LWT 50 79 52 79 / 20 20 10 40

TFX WATCHES/WARNINGS/ADVISORIES

None.