523
FXUS65 KTFX 232336
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
536 PM MDT Sat Aug 23 2025

Aviation Section Updated.

.KEY MESSAGES...

- Most locations will see dry conditions and warming
  temperatures through the middle of next week.

- Smoke from regional wildfires will continue to bring hazy skies
  at times, particularly for areas south of the US highway 12
  corridor.

- Monsoon moisture will bring a day to day increase of shower and
  thunderstorm activity over Southwest Montana beginning Sunday
  evening, with some northward expansion into Central and North-
  central Montana during the second half of the upcoming week.

&&

.DISCUSSION...
/Issued 206 PM MDT Sat Aug 23 2025/

 - Meteorological Overview:

Ridging aloft over the western states will maintain general dry
conditions for most of the Northern Rockies through the mid-week
period. Monsoon moisture and weak perturbations will increasingly
compromise the ridge while the main axis of high pressure migrates
southeastward out of the Great Basin towards Texas and New
Mexico. Sufficient moisture and instability will creep into
Southwest Montana and bring cloud builds and perhaps a few
isolated high based showers or storms as early as Sunday evening.
This activity will increase daily as the week progresses and will
begin to expand northward during the second half of the week as a
trough deepens over the Pacific Northwest and sends additional
moisture and shortwaves into the Northern Rockies.

Lightning and localized, gusty winds will initially be the
primary concerns for the southwest given drier boundary layers and
higher based storms. Moisture does markedly increase Tuesday
through Thursday with PWATs pushing into the 0.75 to 1 inch range
or about 2 to 3 standard deviations above climatology according to
the NAEFS (North American Ensemble Forecasting System). This is
expected to result in more widespread rainfall and locally heavy
convective downpours in addition to the lightning and winds. The
aforementioned deepening trough and shortwave energy will expand
the moisture and associated showers and thunderstorms northward
into Central and North-central Montana heading towards the
weekend. Temperatures warm some in response to the ridging aloft,
but the increasing cloud cover and convective activity will mostly
preclude highs from exceeding the 85 to 90 degree range and may
even lower temperatures below average over the southwest on
Wednesday and Thursday. - RCG

 - Forecast Confidence & Scenarios:

Smoke and haze from regional wildfires...

Smoke from regional wildfires will continue cause skies to become
hazy and even overcast at times through the weekend. While some
visibility and air quality reductions can`t be ruled out,
especially in the late night and early morning hours, there`s a
general expectation for most of the smoke to remain aloft. Areas
along and south of the US highway 12 corridor will be most
susceptible to haze and smoke impacts.

Shower and thunderstorm activity returning and slowly expanding
northward next week...

Weak flow aloft and the lack of defined shortwaves adds
uncertainty on precisely how next week`s shower and thunderstorm
activity will initiate and ultimately unfold, but there is an
expectation for at least cloud builds and and a few stray high
based showers or thunderstorms to develop as early as Sunday
evening for locations south of I90. This activity will slowly
increase and expand northward as the week progresses. CAPE values
generally less than 500 J/kg on Sunday and Monday should keep any
storm development from getting very strong or widespread, but
isolated lighting strikes and localized winds gusts can be
expected with the stronger cores.

Increasing moisture will result in more productive showers and
thunderstorms heading towards the mid-week period. The primary
concern will be heavier downpours falling over burn scars. The
probability for daily rounds of rainfall exceeding a quarter of an
inch or more increases to the 40 to 70% range for locations south
of I90 on Wednesday and Thursday, highest along the Montana and
Idaho border. The moisture does lift northward into Central and
North- central Montana during the second half of the week, but
confidence with how widespread the showers and storms will get is
on the low side given high uncertainty of shortwave placement,
timing, and strength. This is reflected in the NBM probabilistic
guidance with less than a 20% chance for daily quarter inch or
higher rainfall totals north of US highway 12. - RCG

&&

.AVIATION...
24/00Z TAF Period.

The primary concern for this TAF period continues to be smoke and
haze over Central and Southwest Montana. Impacts should mostly be
limited to compromised slantwise visibility and occasional scattered
to broken low VFR ceilings. There also may be a few cloud builds
and perhaps an isolated shower or thunderstorm over the higher
terrain of far Southwest Montana between 24/22 and 25/04Z.
Otherwise, mostly VFR conditions are expected under passing mid-
and high level cloudiness. Surface winds will generally be out of
the east to northeast and will gust in the 10 to 20 kt range at
times. - RCG

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  48  83  49  85 /   0   0   0   0
CTB  45  79  46  83 /   0   0   0   0
HLN  52  85  52  86 /   0   0   0   0
BZN  47  85  46  86 /   0   0   0   0
WYS  38  82  38  80 /   0  10   0  20
DLN  47  84  48  84 /   0   0   0  10
HVR  47  80  47  84 /   0   0   0   0
LWT  46  77  47  80 /   0   0   0   0

&&

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

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