847
FXUS65 KTFX 200529
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1029 PM MST Wed Nov 19 2025

Aviation Section Updated.

.KEY MESSAGES...

 - After lingering showers diminish this afternoon, patchy fog looks
   to develop heading into Thursday morning.

 - Another period of breezy winds across the plains develops Friday
   into Saturday.

 - Confidence increasing in another at least breezy period Monday
   ahead of a trend cooler next week.

&&

.UPDATE...
/Issued 830 PM MST Wed Nov 19 2025/

A few rain/snow showers moving across Southwest MT will dissipate
through the rest of this evening as weak upper level ridging
builds across the Northern Rockies. Skies have cleared across much
of north-central MT with at least partial clearing expected later
tonight across Southwest MT, setting the stage for areas of fog
development. Areas from Cascade County to the southern Rocky Mtn
Front may see the earliest development (by midnight) as skies
have cleared with light winds and dewpoints remain elevated with
some high resolution model guidance indicating the potential for
fog spreading as far north as Cut Bank and Shelby late tonight.
Fog may also develop across Southwest MT valleys later tonight as
skies partially clear. Hoenisch

&&

.DISCUSSION...
/Issued 830 PM MST Wed Nov 19 2025/

 - Meteorological Overview:

Weak troughing associated with a more potent wave further north in
Canada and an upper low in CA will pass across the Northern Rockies
through the remainder of the afternoon before exiting eastward
tonight. Forcing for light rain and snow will wane through the late
afternoon and evening. Additional snow accumulations look light and
focused in the mountains. As skies attempt to clear tonight, at
least patchy fog will develop. Areas most favored for fog will be in
Southwest Montana valleys in addition any other areas that see more
than just a trace of rain or snow through the remainder of the
afternoon and early evening.

Brief shortwave ridging moves in for Thursday, allowing for a dry
day with temperatures trending milder again. Another splitting
trough then moves in across the Pacific NW late Thursday into
Friday, with the main upper disturbance shifting well south of the
region, with a weaker wave staying further north. A largely zonal
flow develops as a result, which will result in at least light
precipitation along the Continental Divide north of Lincoln Friday
into Saturday. Additionally, breezy winds look to return over the
plains Friday (Locally stronger along the Rocky Mountain Front),
lingering through the day Saturday.

The largely zonal flow continues into early next week, with
increasing confidence in a quick moving disturbance moving across
the region Monday into Tuesday. Another period of at least breezy
winds looks to accompany this system, with areas north of Lincoln
along the Continental Divide once again favored for precipitation.

A northwesterly flow aloft look to develop in wake of the
Monday/Tuesday system, which would strongly favor a cooling trend,
with at least low-end probabilities for snow. -AM


 - Forecast Confidence & Scenarios:

Winds Friday into Saturday:

Although cross barrier flow does not look overly impressive from a
magnitude perspective, the combination of strong ridgetop stability
and a building pressure gradient will help to translate these winds
to the surface Friday into Saturday. The probability for a 55 mph
gust in Cut Bank is roughly 50% late Friday into Saturday. Further
west in Browning the probability for a 70 mph gust is around 40%.
Given the lower confidence in stout cross barrier flow and reliance
on a strong pressure gradient developing, I have opted to hold off
from any High Wind Watches at this time for Friday into Friday
night. Trends will continue to be monitored for changes in
confidence for higher impact wind over this timeframe.


Winds Monday:

Ensemble guidance is beginning to key in on another at least breezy
period across the region Monday. Although this is the case, the
range of scenarios remains rather high. The 25th-75th percentile
spread for a max wind gust at Cut Bank is roughly 25 mph (25th
percentile is roughly 40 mph and the 75th percentile is roughly 65
mph). All this to say: Confidence is increasing in a breezy period
Monday, with confidence in specific magnitudes remaining low.


Cooldown Next Week:

After the period of breezy winds Monday, a northwesterly flow aloft
will ensue. Cooler air looks to move in as a result, with daytime
highs falling a touch below average by Wednesday. Although the
probability for precipitation increases toward the middle of next
week, an overly wet scenario is not favored. The probability for
3 inches of snow over the 48 hours prior to Thanksgiving morning
is less than 10% at lower elevations. -AM

&&

.AVIATION...
20/06Z TAF Period

VFR conditions will prevail across all but the KBZN, KEKS, and KCTB
terminals during this TAF Period. Between 20/11Z and 20/18Z there
will be fog at the KBZN and KCTB terminals which will reduce
visibility to at least IFR levels but there is a 20 - 40% chance
that visibility will be reduced to IFR levels. At the KHLN, KGTF,
and KHVR terminals between 20/09Z and 20/17Z there is a 20 - 35%
chance for fog to reduce visibility to at least MVFR levels. For
the first 12 hours of this TAF Period there will be Mountain
obscuration across Southwestern Montana. -IG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  23  52  31  53 /   0   0   0   0
CTB  21  49  27  49 /   0   0   0   0
HLN  26  48  26  50 /   0   0   0   0
BZN  24  49  24  51 /   0   0   0   0
WYS  24  45  17  44 /  30  10   0   0
DLN  26  46  25  49 /  10   0   0   0
HVR  19  45  24  53 /   0   0   0   0
LWT  24  52  29  55 /   0   0   0   0

&&

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

$$
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