390
FXUS65 KTFX 221142
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
442 AM MST Sat Nov 22 2025

Aviation Section Updated.

.KEY MESSAGES...

 - Patchy valley fog in the valleys of Southwest Montana may be
   locally dense on Saturday morning.

 - Gusty winds continue through the weekend, along with above
   normal temperatures and dry overall conditions.

 - A cold front will bring falling temperatures on Monday, along
   with another period of strong winds and increasing
   precipitation chances.

&&

.DISCUSSION...
/Issued 237 AM MST Sat Nov 22 2025/

 - Meteorological Overview:

Zonal flow aloft over the Northern Rockies will help to maintain
above normal temperatures and windy conditions across Southwest
through North Central Montana through the weekend. The warmest
conditions through this timeframe will occur over the plains of
Central and North Central Montana where gusty downsloping winds will
contribute to additional warming and drying. Overall dry conditions
can be expected through the weekend, with increasing precipitation
chance along the Continental Divide from Sunday afternoon as an upper
level shortwave begins to dig into the Pacific Northwest and Pacific
moisture is advected northeastward over the Northern Rockies within
a region of warm air advection.

By Monday the aforementioned upper level shortwave will slide
eastward and over the Northern Rockies, with an attendant cold front
diving southeast from Alberta during the morning through early
afternoon hours. Windy conditions and increasing precipitation
chances will accompany this upper level disturbance and cold front,
along with falling temperatures through the day on Monday. Heaviest
precipitation during the day and overnight hours on Monday is
expected to fall in the mountains. Quasi-zonal to northwest flow
aloft settles in over the Northern Rockies for much of the remainder
of the work week/Thanksgiving, with near to below normal
temperatures and daily chances for rain/snow showers across lower
elevations and mountain snow, especially along the Continental
Divide. - Moldan

 - Forecast Confidence & Scenarios:

Accumulating Snow from Sunday evening through Monday night...

ECMWF EFIs continue to support the potential for a climatologically
unusual snow event throughout the period, particularly along the
Continental Divide north of the Montana Hwy 200 corridor where EFI
values range between 0.5 to 0.7. NBM4.3 probabilities for snowfall
in excess of 4" have changed very little over the past 24 hours,
with the highest values in excess of a 70% chance still residing
over northern portions of the Southern Rocky Mountain and all of the
East Glacier Park Region. Additionally the probability for 6" or
more of snow is in excess of an 80% chance for Marias Pass, with
even a 30% chance for 12" or more of snow. At this time the heaviest
period of snow looks to fall during the afternoon and early evening
hours on Monday, with relatively warm ground temperatures likely to
inhibit snowfall accumulations initially during the daylight hours
on Monday.

Strong Winds on Monday...

Confidence in high winds occurring with and following the passage of
the upper level disturbance and attendant cold front has decreased
over the past 24 hours, but NBM4.3 probabilities do still indicate
the potential for gusts in excess of 48kts. Latest probabilities for
gusts in excess of 48kts now hold at between a 10-30% chance for
most locations along and north of the I-90 corridor, which has been
a 20-40% chance reduction as compared to 24 hours ago. None-the-less
the passage of the upper level wave and surface cold front is still
expected to occur during peak mixing hours, which does support a
better window for the transport of higher momentum to surface.
Additionally, rain/snow showers along and in wake of the font may
also contribute in bringing stronger winds aloft to the surface. We
will continue to monitor this event for future wind highlights, but
for now we will withhold issuing any High Wind Watches given low
probabilistic support.

Late Week System...

Ensemble guidance continues to support a large scale pattern shift
to colder and snowier conditions across the Northern Rockies;
however, significant differences between these ensemble also casts
doubt on the arrival of the coldest temperatures and precipitation.
Those with post Thanksgiving travel plans should continue to monitor
future forecast as impacts to travel, most notably over mountain
passes, are likely at some point between Friday and next Sunday. -
Moldan


&&

.AVIATION...
22/12Z TAF Period

Scattered to broken low clouds over Southwest Montana, generally
along and south of the I-90 corridor, will reduced CIGS to
between 6-9kft through 16-18z Saturday. Additionally, patchy fog
was attempting to develop on the edge of these low clouds,
specifically near the KBZN terminal, but confidence in reductions
in VIS occurring at the terminal remained too low for any
prevailing mention outside of vicinity fog. Otherwise VFR
conditions will prevail throughout the 2212/2312 TAF period, with
gusty southwest to west winds once again occurring over the
plains of Central and North Central Montana. Mountain obscuration
will continue over Southwest Montana through the morning hours. -
Moldan

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  56  43  56  38 /   0  10  10  20
CTB  51  38  52  29 /  10  10  20  30
HLN  51  29  51  31 /   0   0   0  30
BZN  51  22  51  29 /   0   0   0  20
WYS  41  17  43  23 /  10   0   0  10
DLN  49  25  50  25 /   0   0   0  10
HVR  53  33  57  31 /   0   0  10  30
LWT  55  34  58  33 /   0   0   0  20

&&

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

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