Wildfire in Montana, August 19 to 31, 2025

Area Forecast Discussion
National Weather Service Great Falls MT
713 AM MDT Tue Aug 19 2025

.KEY MESSAGES...

 - Hot temperatures expected today with temperatures reaching the
   low to mid 90s across the lower elevations.
 - Isolated showers and thunderstorms this afternoon and evening,
   some could produce some gusty winds.
 - Not as warm after Wednesday through the weekend, but
   temperatures trend back upwards for the weekend.

&&

.UPDATE...

A building upper ridge and associated H5 height rises will
support temperatures rising well above average across the region
today. The thought is that the peak of the heat will only be
today, with overnight relief tonight before a warm, but not overly
hot day Wednesday. Hence, no Heat Advisories are being considered
at this time.

After peak heating today attention then turns to a wave
progressing through the southwesterly flow aloft across western
and North-central Montana this evening. This looks to result in at
least widely scattered showers and thunderstorms, initially west
of the Continental Divide early this evening, which spread across
North-central Montana late evening into the overnight. The depth
of the sub-cloud layer and overall magnitude of DCAPE should help
downdrafts to overcome the building (and largely shallow) surface
inversion over the plains tonight, hence resulting in a threat for
strong wind gusts from the most robust thunderstorms.

Overall minor changes were made this morning to account for
current trends. -AM

&&

.DISCUSSION... /Issued 403 AM MDT Tue Aug 19 2025/

 - Meteorological Overview:

Upper level ridging building across the Western US will bring
increasing temperatures to the Treasure State today and Wednesday,
with temperatures rising into the 90s for most lower elevation
locations this afternoon. While most of us will be dry today, a
few isolated showers and thunderstorms are expected to develop
across the Plains late this evening. Depending on the timing of
these storms, I can’t rule out a few strong to severe wind gusts.
However, most of these should push through the area late in the
evening as temperatures begin to fall for the night, resulting in
an inversion that should keep wind gusts just above the surface.
With that said, some localized higher elevations could still see
some isolated gusts from these storms.

Our upper level ridge will begin to break down on Wednesday as an
upper level tough pushes through Alberta, which will keep our
temperatures slightly cooler Wednesday afternoon, but will also
result in increased wind gusts and a few isolated to scattered
showers and thunderstorms in the afternoon. Again, some of the
storms may produce some stronger wind gusts, particularly before 8
or 9PM when our inversion will set up again.

As we head into the later part of the week, upper level ridging
will set up to our west, resulting in northwesterly flow aloft
over us and high pressure at the surface. This will keep us fairly
dry and calm, with temperatures not quite as warm with highs
generally in the 80s across the lower elevations. Ludwig

&&

.AVIATION...
19/12Z TAF Period

The initial concern this TAF period will be for patchy smoke from
regional wildfires. Slant-range visibility reductions look to
be more common than surface visibility reductions through the day
today.

Attention then turns to this evening and overnight, when a period
of showers and thunderstorms is forecast, mainly over the plains
of North-central Montana. Lightning and gusty erratic winds are
the main concern with thunderstorms that do form.

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

&&

.FIRE WEATHER...

Fire weather concerns will continue through Tuesday and Wednesday
with highs in the 90s expected across the plains and valleys across
the region. Minimum RH values will range from the single digits to
the mid teens with Tuesday expected to be the warmest and driest day
of the week. Winds are less of a concern these days, however, an
isolated afternoon dry thunderstorm cannot be ruled out which will
keep fire weather concerns elevated until a cold front passes
through late Wednesday into Thursday. -thor

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  96  60  92  55 /   0  30   0  20
CTB  90  58  86  49 /  10  50  10   0
HLN  96  60  92  56 /   0  20   0  20
BZN  96  54  93  53 /   0   0  20  20
WYS  86  47  85  42 /   0   0  20  20
DLN  92  52  90  50 /   0   0  20  20
HVR  96  62  93  55 /   0  40   0  20
LWT  93  58  88  54 /   0   0   0  40

&&

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

http://www.weather.gov/greatfalls