Whitefish Mountain

000
FXUS65 KTFX 221748
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1148 AM MDT Sat Aug 22 2026

Aviation Section Updated.

.KEY MESSAGES...

- Scattered showers and thunderstorms today, some storms
  will contain strong, gusty winds, heavy downpours capable of
  localized flooding over burn scars, and dangerous cloud to
  ground lightning.

- A surface front will bring gusty winds and elevated fire weather
  conditions on Sunday, there will also be a few lingering 
  showers and storms east of I15, some may be strong to severe.

- There will be a modest cooldown early next week with some widely
  scattered showers and storms, mostly over southwest Montana.

&&

.UPDATE...
/Issued 641 AM MDT Sat Aug 22 2026/ 

A small update was made this morning to reflect latest trends in
showers. There is no change in thinking with respect to showers
and thunderstorms this afternoon and evening. Gusty winds and
briefly heavy rain will be the primary concerns today. -AM

&&

.DISCUSSION...
/Issued 641 AM MDT Sat Aug 22 2026/ 

 - Meteorological Overview:

A subtle shortwave moving through an increasingly southwesterly 
flow aloft is bringing scattered showers and isolated 
thunderstorms this morning. This activity will continue to weaken 
as it moves northeastward, but may produce localized gusty winds, 
lightning, and brief downpours. Stronger forcing associated with a
trough approaching from the Pacific NW still looks to send a more
impactful wave of showers and thunderstorms through the forecast 
area later this afternoon and evening. 

ML CAPE looks to generally fall in the 400 to 900 J/kg range for 
most locations, but there are some pockets with values as high as 
1500 J/kg over portions of central and southwest MT. Very warm and
dry boundary layers will increase instances of strong gusty winds
up to and exceeding 60 mph, especially if linear upscale growth 
takes place. Hail and brief downpours capable of flash flooding of
normally flood prone areas will also be present with effective 
shear generally above 25 kts and PWATS surpassing the one inch 
mark in some areas. The focus of this activity will be over 
southwest MT and and along the Continental Divide, although at 
least some of it will move northeastward onto the plains during 
the late evening and perhaps the overnight hours.

The Pacific NW trough will swing northeastward through W MT and 
into Canada on Sunday while its attendant surface front traverses 
the CWA and brings gusty westerly winds and elevated fire weather 
conditions. There will also be lingering instability for widely 
scattered showers and thunderstorms, with some on the strong side,
mainly for locations east of I15. Temperatures modestly cooldown 
Monday and Tuesday with some shower and thunderstorm activity in 
southwest MT. This looks to be followed by ridging aloft briefly 
rebuilding before a couple Pacific troughs move through the 
Northern Rockies during the mid to latter part of next week. These
systems will bring more showers and thunderstorms ahead of them 
followed by gusty westerly winds in their wake. - RCG

 - Forecast Confidence & Scenarios:

Scattered strong thunderstorm activity through Sunday...

Higher quality forcing brings more impactful showers and 
thunderstorms this afternoon and evening. Strong gusty winds in 
excess of 60 mph and lightning will be the primary hazards, 
especially if the storms become linear and undergo upscale growth.
This threat will be highest over southwest MT and along the 
Continental Divide. Some weakening is expected with this activity 
as it moves northeastward, though these same hazards apply to 
plains locations as well. In addition to the winds, there will be 
localized heavy downpours capable of flash flooding of burn scars 
and other flood prone locations, mainly in central and southwest 
MT where there is around a 10% chance for excessive rainfall and 
localized flooding. While this activity will be monitored for the 
aforementioned flash flooding, I will continue to hold off sending
out flood products per the more scattered nature of higher 
rainfall rates and progressive storm motion. The focus of this 
activity shifts eastward on Sunday with a few stronger storms for 
locations east of I15. Central/north-central locations east and 
southeast of the highway 87 corridor will see the strongest storm 
ceiling with strong, gusty winds, hail, and downpours all on the 
table. - RCG

&&

.AVIATION...
22/18Z TAF Period 

VFR conditions will prevail throughout this TAF period, with the 
exception of periods of MVFR conditions due to a passing 
thunderstorm. Thunderstorms will begin to develop in Southwest MT 
around 21Z, moving northeast throughout the evening. While 
confidence was too low in thunderstorms reaching KHVR to include 
in the TAF, an isolated thunderstorm cannot be ruled out. Any 
thunderstorms that develop will be capable of producing gusty, 
erratic winds, brief, heavy downpours, frequent lightning and 
hail. Periods of mountain obscuration will develop due to passing 
thunderstorms. 

For KGTF: Thunderstorms are expected to begin moving over KGTF as
early as 01Z, and will be capable of producing gusty, erratic 
winds greater than 40 kt, frequent lightning, brief, heavy 
downpours and hail. Thunderstorms are expected to exit the area 
around 06Z. Outside of any gusty, erratic winds a thunderstorm may
produce, the chance of a cross-wind greater than 15 kts is less 
than 10% due to a southwesterly direction. -Dzomba

&&

.FIRE WEATHER...

Widely scattered showers and storms with cloud to ground 
lightning and little or light precipitation will continue to 
weaken this morning as they move northeastward. Even though this 
activity is of lower grade, some new fire starts can't be ruled 
out. More productive storms move in this afternoon and evening, 
but increased cloud to ground lightning activity may still ignite 
new fire starts. 

The most cornering fire weather day will be on Sunday when a 
surface front brings gusty westerly winds amid continued very warm
and dry conditions. The timing of this front will ultimately 
determine how long the dry and windy conditions persist. The 
latest NBM probabilistic guidance continues to highlight large 
areas of north- central and portions of southwest Montana with 
over a 70% chance for wind gusts over 30 mph. Although the fuels 
aren't quite as dry as they were in earlier in the month, elevated
fire conditions will be present and the wind may be enough to 
ignite any lightning caused hold over fires from Friday and 
Saturday's storms. In addition to the winds, there will be more 
widely scattered showers and thunderstorms, some with strong, 
erratic wind gusts. - RCG 

&&

.HYDROLOGY...

The combination of increased monsoonal moisture aloft and lower 
level moisture moving in from the east today will result in a 10% 
chance for localized heavy thunderstorm rains producing flash 
flooding over and near burn scars, urban areas, and other normally 
flood prone locations. While this activity will be monitored for the 
aforementioned flash flooding, a flash flood watch will issued with 
this forecast package per the more scattered nature of higher 
rainfall rates and progressive storm motion. The moisture profile 
begins thin on Sunday, which will reduce the threat for excessive 
rainfall through early next week. - RCG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  90  61  89  53 /  30  40  20   0 
CTB  85  57  81  50 /  30  20  20   0 
HLN  90  57  87  52 /  30  60  30   0 
BZN  87  53  86  50 /  50  40  40  10 
WYS  81  45  78  41 /  50  40  30  10 
DLN  86  52  85  48 /  40  60  10   0 
HVR  93  61  93  55 /  20  10  40  20 
LWT  88  59  89  52 /  20  30  40  20 

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
&&

$$
http://www.weather.gov/greatfalls