837
FXUS65 KTFX 221100
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
500 AM MDT Tue Sep 22 2026

Aviation Section Updated.

.KEY MESSAGES...

 - Above average warmth through Friday.

 - Scattered showers and isolated thunderstorms primarily across
   southwest MT this evening and overnight.

 - Pacific weather system brings windy and cooler conditions for the
   upcoming weekend.

&&

.DISCUSSION...
/Issued 206 AM MDT Tue Sep 22 2026/

 - Meteorological Overview:

Large scale ridging centered east of the region will maintain above
average warmth and a southwesterly flow aloft across the Northern
Rockies and MT through Friday before a broadening upper trough in
the North Pacific edges inland this weekend. An upper level
disturbance and some monsoon-related moisture embedded within the
southwesterly flow around the ridge will spread increasing cloud-
cover northward across the area today with scattered showers and
isolated weak thunderstorms tracking across primarily SW MT late
this afternoon through tonight. The warmest temperatures this week
are likely Thursday and Friday as southwesterly flow increases
ahead of the incoming upper trough with afternoon temperatures
pushing well into the 80s for many areas. This would be around 15
degrees above seasonal averages but well below daily records, which
are still in the lower to mid 90s.

A relatively strong Pacific cold front is forecast to traverse the
northern Rockies late Friday into Friday night. However, model
discrepancies persist regarding the precise timing and intensity of
the embedded shortwave as it lifts northeastward from the Northern
Rockies into AB by Saturday morning. Gusty southwest winds are
likely to precede the front late Friday with showers and potentially
some thunderstorms accompanying the frontal passage, followed by
gusty west winds and cooler temperatures for the weekend.

 - Forecast Confidence & Scenarios:

Instability will be constrained this afternoon due to high cloud-
cover and decreasing late September solar input, keeping CAPE values
mostly under 500 J/kg. Consequently, thunderstorm threats will be
limited primarily to isolated lighting strikes and wind gusts to
around 30 mph.

The main hazard to watch with the approaching Pacific trough and cold
front early this weekend remains the potential for elevated winds
Friday night into Saturday. Recent model guidance has shifted the
shortwave slightly further north however, and somewhat weakened
the accompanying mid-level wind field. The overall setup, featuring
downward transport of winds following the shortwave and moderate
pressure rises in the wake of the front, continues to support the
potential for locally strong winds gusts and probabilistic guidance
now indicates a 30-40% chance of gusts exceeding 55 mph along the
Rocky Mountain Front and adjacent areas on Saturday. Hoenisch

&&

.AVIATION...
22/12Z TAF Period.

Fog development early this morning is mainly limited to areas near
the Milk River and upper Missouri breaks, but will include the KHVR
vicinity, where LIFR cigs/vis are possible through 16z. Elsewhere,
VFR conditions prevail with an increase in mid to high level
cloud-cover from south to north through this afternoon. Scattered
showers and a few isolated/weak thunderstorms develop across
southwest MT late this afternoon and look to track as far north as
near KHLN and KLWT overnight. Some local mountain obscuration and
brief MVFR conditions are possible near showers this evening/overnight.
Hoenisch

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  80  52  80  49 /   0   0   0   0
CTB  77  48  73  45 /   0   0   0   0
HLN  77  49  77  48 /  10  20   0   0
BZN  75  47  75  45 /   0  30   0   0
WYS  66  35  64  30 /   0  60   0   0
DLN  73  43  74  42 /  10  40   0   0
HVR  80  50  81  47 /   0   0  10   0
LWT  79  50  77  48 /   0  20  20   0

&&

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

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