390
FXUS65 KTFX 212337
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
437 PM MST Fri Nov 21 2025

Aviation Section Updated.

.KEY MESSAGES...

 - Valley fog may return to the valleys of Southwestern Montana
   overnight tonight.
 - First signs of an upcoming pattern change arrive Monday with
   cooler temperatures and some mountain snowfall.
 - A more significant pattern change looks to arrive late next
   week, bringing the coldest air of the season so far and the
   possibility of snow to all elevations.

&&

.DISCUSSION...
/Issued 251 PM MST Fri Nov 21 2025/

 - Meteorological Overview:

Weak upper level ridging over the Northern Rockies today will
persist through the weekend, keeping temperatures slightly above
average for this time of year along with mostly benign weather
conditions. However, as we head into next week, a shortwave trough
will push through the Northwestern United States, which will
usher in a round of cooler and unsettled weather to the area.
While snowfall should generally be confined to the higher terrain,
a few of the lower elevation locations in and around Great Falls
may also see some light snowfall as this system passes through
Monday and Tuesday.

Behind this system, we will return to more of a ridging patter
aloft, but temperatures will remain near to below average here at
the surface thanks to a surface high pressure system over Southern
Alberta. However, this high pressure system will not last long as
the next weather system begins to push into the Pacific Northwest
for Thanksgiving Day. While this will generally only result in
some snowfall across the Continental Divide north of Lincoln, some
gusty winds are likely across the plains Thanksgiving Day as
well.

The coldest air of the season so far will likely begin to surge
into the area from the north on Friday as a plume of moisture
makes its way up from the southwest. As these meet, a widespread
and potentially impactful snowfall is possible across at least
some of the area as folks travel back from the Thanksgiving
holiday and/or post-Thanksgiving errands. Ludwig

 - Forecast Confidence & Scenarios:

High Wind Potential on Monday...

Climate anomaly indicators such as the NAEFS and ECMWF EFIs suggest
the potential, albeit limited, for a climatologically unusual period
of winds Monday morning/afternoon with the passage of an upper level
shortwave and cold front. H700 wind speeds per NAEFS analysis
support values approaching 50kts overspreading portions of Southwest
and North Central Montana between 12-18z, which are nearly 2
standard deviations above normal. ECMWF EFIs with respect to wind
gusts range from between 0.5 to 0.6 north of the I-90 corridor and
south of the MT Hwy 200 corridor, with the highest values located
along the Continental Divide (i.e. MacDonald Pass area). NBM4.3
probabilities for wind gusts in excess of 48kts across lower
elevations generally range from a 25-50% chance along and southwest
of a Cut Bank, to Great Falls, to Judith Gap line and along and
north of the I-90 corridor. -Moldan

Accumulating Snow on Monday...

NBM4.3 probabilities for snowfall accumulations in excess of 4" from
late Sunday night through Monday night are in excess of a 70% chance
north of the Benchmark area along the Continental Divide, with even
a 30% chance in the Little Belts of Central Montana. Additionally
there is 60% or greater chance for snowfall accumulations of 6" or
more for the Marias Pass and Logan Pass areas over this same
timeframe, with ECMWF EFIs with respect to snow across the East
Glacier Park Region now in excess of 0.5. These increasing
probabilities and EFI values suggest the growing potential for some
winter weather related impacts to those traveling  on US Hwy 2 west
of Browning during the day on Monday. - Moldan

Late Week System...

Models continue to suggest that late next week could be on the
snowy and cold side as a big pattern change continues to come into
increase in likelihood. Current NBM probabilities have continued
to slowly adjust upward for a few inches of snow late next week
for just about the entire state, and while temperatures remain a
bit uncertain at this range most areas north of the Little Belt
and Snowy Mountains have at least a 5 to 10% chance of seeing
temperatures dip below the 0 degree mark Friday night. Those with
interests in post-Thanksgiving travel should continue to monitor
the forecast as the event approaches, as the timing of this event
could result in some higher than normal impacts. Ludwig


&&

.AVIATION...
22/00Z TAF Period

The initial concern this TAF period will be for lingering gusty
surface winds across the plains, which will continue to diminish
into the remainder of the evening. Attention then turns to
Southwest Montana valleys late tonight for additional patches of
fog. Scattered upper level cloudiness may end up mitigating
concerns for fog development, but there was enough confidence to
include a VCFG mention for KBZN late tonight into early Saturday.

Another period of gusty surface winds is forecast to develop for
areas near and west of I-15 on the plains Saturday from late morning
through the afternoon. -AM

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  34  55  40  55 /   0   0   0   0
CTB  29  50  36  52 /   0   0   0   0
HLN  28  50  28  51 /   0   0   0   0
BZN  25  50  23  51 /   0   0   0   0
WYS  22  40  17  43 /   0   0   0   0
DLN  26  49  24  49 /   0   0   0   0
HVR  27  52  32  57 /   0   0   0   0
LWT  29  55  34  58 /   0   0   0   0

&&

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

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