Wildfire in Montana, September 1 to 30, 2025

Area Forecast Discussion
National Weather Service Great Falls MT
1118 PM MDT Sun Aug 31 2025

Aviation Section Updated.

.KEY MESSAGES...

 - Temperatures will be hot this afternoon through Tuesday before
   cooling Wednesday through Friday.

 - Each day this week there is at least a low chance for isolated
   showers with chances peaking towards the end of the work week.

 - There will be smoke/haze around North-central, Central, and Southwestern
   Montana for at least the next couple of days due to wildfires
   in the region.

&&

.UPDATE...
/Issued 852 PM MDT Sun Aug 31 2025/

Ridging aloft will maintain mostly fair conditions tonight into
Monday, but a bit of instability and moisture initiated a few
isolated showers and storms earlier this afternoon and evening.
Most of this activity has since faded out with the loss of diurnal
heating, but a few cells will move eastward towards the Northern
Rocky Mountain Front and nearby high plains through around
midnight. Cloud to ground lightning and gusty winds up to around
35 mph will be the primary impact. Otherwise, hazy skies from
regional wildfire smoke can be expected for the overnight hours.
- RCG

&&

.DISCUSSION...
/Issued 852 PM MDT Sun Aug 31 2025/

 - Meteorological Overview:

This afternoon there is an upper-level ridge over North-central,
Central, and Southwestern Montana. This will allow temperatures to
warm up this afternoon with mostly dry weather. The upper-level
ridge will remain over North-central, Central, and Southwestern
Montana on Monday. This will allow temperatures to warm up further
to well above seasonal averages with mostly dry weather on
Monday. Due to southwest upper-level flow it will be hazy and
smoky across North-central, Central, and Southwestern Montana this
afternoon through Monday due to regional wildfires. On Tuesday
the upper-level ridge remains over North-central, Central, and
Southwestern Montana with strong northwest flow aloft. This will
cool temperatures down a few degrees along the Hi-line with above
seasonal average temperatures for the rest of North-central,
Central, and Southwestern Montana. Also due to the northwest flow
aloft there is the potential for very isolated showers Tuesday
afternoon and evening. Due to the hot temperatures on Tuesday
combined with the northwest flow aloft there is also the potential
for isolated thunderstorms.

Wednesday through Friday the upper-level ridge remains over North-
central, Central, and Southwestern Montana with strong northwest
flow aloft. This will cool temperatures down but they will remain
above seasonal averages each day Wednesday through Friday. Due to
the northwest flow aloft there will be isolated showers each day
Wednesday through Friday. On Saturday the upper-level ridge remains
over the area with weak upper-level flow. This will keep warm
temperatures around with mostly dry weather.

 - Forecast Confidence & Scenarios:

There is a 25 - 40% chance for high temperatures of 90 degrees or
greater around/near Fort Benton, Great Falls, the Helena Valley, and
the Gallatin Valley on Monday. On Tuesday there is a 25 - 50% chance
for a high of 90 degrees or greater for the lower elevations near
and along I-15 from Great Falls through the Helena Valley. On
Tuesday there is less than a 20% chance for thunderstorms across
North-central, Central, and Southwestern Montana. However due to
there being northwest flow aloft those probabilities are too low.

Overall there is high confidence in the overall pattern for this
forecast period. The biggest uncertainty is where and if showers
will form each afternoon today through Friday. Since northwest flow
increases in strength Tuesday through Friday, those days have the
highest probability for isolated showers.

Looking out a bit beyond this forecast period there is growing
confidence in a significant cooldown around September 9th. 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 9th. The deterministic ECMWF (European
Model) has also been hinting at a cool down with less run to run
consistency than the GFS. The deterministic ECMWF also has the cool
down being a day or two later than the deterministic GFS. -IG

&&

.AVIATION...
01/06Z TAF Period.

VFR conditions are expected to prevail through the period.

Smoke and haze will be an ongoing concern across the region
through at least 02/00Z with the main impact being degraded
slantwise visibility. At this time there is low confidence in
surface-level impacts as the worst of the smoke looks to stay
aloft through the period.  -thor

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  55  89  55  88 /  10  10  10   0
CTB  51  87  52  83 /  20  10  20   0
HLN  57  90  57  90 /  10   0   0   0
BZN  51  89  51  88 /   0   0   0   0
WYS  37  80  39  80 /  10   0   0   0
DLN  47  83  49  85 /  10   0   0   0
HVR  55  87  55  83 /   0   0  10  10
LWT  55  84  54  83 /   0   0  10  10

&&

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

http://www.weather.gov/greatfalls