430
FXUS65 KTFX 312023
AFDTFX

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

.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...

 - 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...
31/18Z TAF Period

VFR conditions are expected to prevail for the next 24 hours as
high pressure moves though Montana. Winds will largely be light
and variable. Only concern is a 30% chance of a shower near KWYS
late Tuesday morning. SHRA/TSRA will eventually move into SW MT
during the afternoon Tuesday.

For KGTF: With light and variable winds in the forecast, there is
a near zero percent chance of crosswinds over 15 kts through 18z
Tuesday. The chance will increase on Tuesday afternoon as some
southeasterly winds gust to around 15 kts. Ludwig


&&

.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