724
FXUS65 KTFX 292025
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
225 PM MDT Fri Aug 29 2025

.KEY MESSAGES...

 - This afternoon rain showers will continue across much of
   Central and North-central Montana with isolated showers on
   Saturday in Blaine and Fergus County.

 - This afternoon it will be cool with temperatures warming up
   Saturday through Monday.

 - Saturday morning patchy fog will form across portions of North-
   central, Central, and Southwestern Montana.

&&

.DISCUSSION...

 - Meteorological Overview:

This afternoon there will be weak upper-level flow over North-
central, Central, and Southwestern Montana. Due to a surface high,
monsoonal moisture is being pulled into Montana. Due to this
combined with vorticity maximums aloft there will be scattered
showers across most of North-central and Central Montana on Friday.
Due to surface heating that has occurred, this afternoon and
evening across North-central and Central Montana there will be
isolated thunderstorms. On Saturday morning due to the recent
rainfall any areas that have clear skies will see patchy fog. On
Saturday an upper-level level ridge will build back in over North-
central, Central, and Southwestern Montana. This will warm
temperatures back up with dry weather except in Fergus and Blaine
county where there will be isolated showers around.

On Sunday and Monday the upper-level ridge remains over North-
central, Central, and Southwestern Montana. This will allow
temperatures to warm up further with mostly dry weather. On Tuesday
a weak cold front will move through North-central, Central, and
Southwestern Montana which combined with strong northwest flow
aloft will cool temperatures down and bring precipitation chances
to the area. On Wednesday an upper-level ridge builds back in
over North-central, Central, and Southwestern Montana with strong
northwest flow aloft. This will cool temperatures down further
with precipitation chances for the area. The upper-level ridge
will remain over North-central, Central, and Southwestern Montana
on Thursday which will allow temperatures to slowly warm back up
with mostly dry weather

 - Forecast Confidence & Scenarios:

There is a 30 - 50% chance for dense fog to form in central
Glacier through Toole County Saturday morning. There is a 10 - 30%
chance for fog across North-central, Central, and Southwestern
Montana Saturday morning. Overall there is high confidence in the
upper-level pattern for this forecast period. However, on Monday
evening/night some models bring a weak cold front while others do
not. Other models bring the cold front on Tuesday evening/night.
As a result on Tuesday and Wednesday there is high uncertainty in
the forecast.

Looking out a bit beyond this forecast period there is growing
confidence in a significant cooldown around September 8th. The
deterministic GFS has been exhibiting very good run to run
consistency with this cool down. The only discrepancy is how cold it
will get around September 8th. The deterministic ECMWF (European
Model) has also been hinting at a cool down around September 8th with
less run to run consistency than the GFS. -IG

&&

.AVIATION...
29/18Z TAF Period.

Scattered to numerous showers and isolated thunderstorms are
expected along and north of a KHLN to KLWT line though 00-06z
Saturday, with isolated showers and thunderstorms to as far south
as the I-90 corridor. Low-VFR/VFR conditions will predominately
prevail through the 2918/3018 TAF period, but temporary MVFR
conditions are likely beneath the heavier showers and
thunderstorms between 21z this afternoon and 03z Saturday north of
the KHLN to KLWT line. Mountains will be obscured through 03-15z
Saturday, with improving conditions from southwest to northeast.
Otherwise the only other concern over the next 24 hours will be
fog development during the morning hours on Saturday, most notably
in the valleys of Southwest and Central Montana. At this time
there is a 20% chance for MVFR VIS due to this fog at the KBZN
terminal between 09-15z Saturday. - Moldan

Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.

&&

.HYDROLOGY...
There is still a small chance that a stronger thunderstorm could
produce some heavy rainfall in a short time today. The probability
is low, generally less than 5 percent, with the highest
probability in the Stanford, Lewistown and White Sulphur Springs
area. Brusda

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  53  83  53  87 /  50  10   0   0
CTB  48  82  50  86 /  30  10   0   0
HLN  53  84  54  87 /  30  10   0   0
BZN  49  81  49  84 /  20  10   0   0
WYS  37  74  36  76 /  10  10   0   0
DLN  45  77  45  81 /  10   0   0   0
HVR  55  77  53  86 /  50  20  10   0
LWT  51  76  53  81 /  60  20  10   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&

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