757
FXUS65 KTFX 202321
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
521 PM MDT Sun Sep 20 2026

Aviation Section Updated.

.KEY MESSAGES...

 - Above average temperatures return this week.
 - Patchy fog early Monday morning.
 - Next system arrives late week bringing wind and rain.

&&

.DISCUSSION...
/Issued 155 PM MDT Sun Sep 20 2026/

 - Meteorological Overview:

Southwesterly upper level flow will be the predominant weather
pattern this week as upper level ridging stalls out over the
center of the North American Continent this week, keeping us
generally warm and dry for most of this week. Expect temperatures
to generally be either side of 80 along the Missouri River
corridor, with temperatures not as warm in the higher terrain and
along the Rocky Mountain Front. Winds will also be
uncharacteristically light for much of the week, with winds
generally struggling to gust over 20 mph through Thursday. Our
next weather system will arrive Friday or Saturday, which will
bring cooler temperatures, gusty winds, and the possibility for
some widespread precipitation, though the amount of rainfall
remains fairly uncertain at this point in time.

 - Forecast Confidence & Scenarios:

Friday/Saturday system: an upper level trough and associated
surface front embedded in the upper level flow are expected to
arrive in the Northern Rockies Friday or Saturday. Current model
forecasts suggest that this setup will bring some widespread
precipitation, with the potential for many areas to receive over a
quarter inch of liquid equivalent. The other concern will be the
wind, as the strengthening trough may produce a bit of a sting jet
on its southwest side, which would produce some gusty westerly
winds thanks to the sinking air behind a cold front. As of Sunday
afternoon, probabilities for 60 mph wind gusts appear low
(generally under 20 percent), but this event will need to be
watched in case probabilities increase. Ludwig

&&

.AVIATION...
21/00Z TAF Period

Weak ridging aloft moves over the Northern Rockies tonight into
Monday and brings mostly clear skies and light winds; however,
lingering surface moisture combined with the light wind regime will
encourage areas of fog to develop, most widespread along the Hi-
Line between 21/09 and 21/16Z. Probabilities for visibility
falling below a half mile are currently running highest (above
50%) for KHVR and KCTB. Other than the categorical degradations
from morning fog/low stratus, general VFR conditions will
prevail. - RCG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  46  79  49  80 /   0   0   0   0
CTB  44  76  45  77 /   0   0   0   0
HLN  44  76  45  77 /   0   0   0   0
BZN  39  73  41  75 /   0   0   0   0
WYS  27  67  28  69 /   0   0   0   0
DLN  39  72  40  74 /   0   0   0   0
HVR  45  79  47  81 /   0   0   0   0
LWT  42  75  46  79 /   0   0   0   0

&&

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

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