998
FXUS65 KTFX 312355
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
555 PM MDT Mon Aug 31 2026

Aviation Section Updated.

.KEY MESSAGES...

 - It will be windy across North-central, Central, and
   Southwestern Montana on Wednesday and Thursday.

 - Showers and thunderstorms return Tuesday and continue through
   at least the end of the work week.

 - It will warm up through Tuesday then cool off to end the work
   week.

&&

.DISCUSSION...
/Issued 223 PM MDT Mon Aug 31 2026/

 - Meteorological Overview:

This afternoon there is an upper-level ridge over North-central,
Central, and Southwestern Montana. This will allow temperatures to
warm up with mostly dry weather. On Tuesday the upper-level ridge
remains over North-central, Central, and Southwestern Montana. This
will allow temperatures to warm up to above seasonal averages.
Tuesday evening an upper-level shortwave will move through the ridge
and bring showers and thunderstorms to Southwestern Montana. On
Wednesday an upper-level trough begins to move over North-central,
Central, and Southwestern Montana. This will allow temperatures to
cool down slightly with showers and thunderstorms across the area.
Due to strong southerly flow aloft and strong low-level winds it
will be windy across North-central, Central, and Southwestern
Montana on Wednesday with the strongest winds along the Rocky
Mountain Front and in north-south orientated valleys.

On Thursday the upper-level trough remains over North-central,
Central, and Southwestern Montana. This combined with strong
southerly flow aloft and strong low-level winds will bring another
day of windy conditions to the area. On Thursday there will be
another day of showers and thunderstorms. On Friday an upper-level
low is over Washington and Oregon with southwest flow over North-
central, Central, and Southwestern Montana. This will allow
temperatures to be around seasonal averages with another day of
showers and thunderstorms and breezy conditions. -IG

 - Forecast Confidence & Scenarios:

On Wednesday and Thursday there is a 40 - 80% chance for wind gusts
of 45 mph or greater across Southwestern Montana. On Wednesday and
Thursday there is greater than a 50% chance for sustained winds of 40
mph or greater in the Madison River Valley. As a result a High Wind
Watch was issued for the Madison River Valley from Wednesday
afternoon through Thursday evening. On Wednesday and Thursday there
is a 30 - 60% chance for wind gusts of 35 mph or greater across
North-central Montana. On Friday there is a 40 - 80% chance for wind
gusts of 30 mph or greater across North-central, Central, and
Southwestern Montana with the greatest probability in Southwestern
Montana and along the Rocky Mountain Front.

On Tuesday there is a 15 - 30% chance for thunderstorms across North-
central, Central, and Southwestern Montana. On Wednesday there is a
15 - 30% chance for thunderstorms across most of North-central,
Central, and Southwestern Montana. On Friday there is a 15 - 30%
chance for thunderstorms across Southwestern Montana. On Tuesday
there is a 50% chance for a quarter inch of rain or greater across
Northwestern Beaverhead County.

On Saturday and Sunday there are significant differences in the
track of the upper-level pattern in the deterministic models and
ensembles. One scenario is that the closed low remains situated
over Washington/Oregon. This would keep status quo weather with
seasonal temperatures and precipitation chances. Another scenario
is that the closed upper-level low splits with one part going
south and the other portion going up into Canada. This would bring
breezy conditons to Hi-Line with some precipitation primarily
confined to the Hi-Line. A third scenario is that the upper-level
low moves east and weakens some. This would bring cooler and
wetter conditions to North-central, Central, and Southwestern
Montana. -IG

&&

.AVIATION...
01/00Z TAF Period

VFR conditions will continue for the TAF period as high pressure
continues to shift east. Winds will be light and variable across
all terminals. Focus shifts to KWYS on Tuesday morning with light
rain showers approaching from the southwest lasting into the early
afternoon. Periods of mountain obscuration around KWYS will be
possible due to passing showers.

For KGTF: VFR Conditions with light and variable winds across the
TAF period. A near zero percent chance of crosswinds exceeding
15kts through the TAF period.
-JR

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  48  85  56  81 /   0   0  20  50
CTB  45  82  51  76 /   0   0  10  50
HLN  48  86  51  79 /   0  10  60  70
BZN  46  81  48  78 /   0  20  70  30
WYS  36  68  36  65 /  10  40  60  10
DLN  44  81  45  76 /   0  10  80  40
HVR  46  88  54  86 /   0   0  10  40
LWT  47  83  53  82 /   0  10  20  30

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Watch from Wednesday afternoon through Thursday
evening for Madison River Valley.

&&

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