869
FXUS65 KTFX 300556
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1156 PM MDT Sat Aug 29 2026

Aviation Section Updated.

.KEY MESSAGES...

 - Showers and thunderstorms overnight, some of which could
   produce gusty winds and brief downpours.

 - Cool and breezy Sunday with highs in the 60s for most lower
   elevation locations, with 50s in the mountains.

 - Drier Monday, but showers and thunderstorms return by Tuesday.

&&

.UPDATE...
/Issued 801 PM MDT Sat Aug 29 2026/
Current forecast that is out looks valid, no updates planned for
at this time. The stronger thunderstorms from earlier this evening
have mostly pushed north/east of the CWA. The main concern for the
rest of tonight is where the band of steadier rain develops per
the NAM/GFS models. This band of rain should develop over
Southwest MT around Midnight, then move northeastward up towards
Central MT by daybreak. Rainfall of 0.20 to 0.40 inches is
possible with that area of precipitation overnight into Sunday
morning. Cooler air will also move into the CWA by Sunday morning,
changing the rain to snow, mostly for elevations above 8000 feet.
Otherwise, temperatures look on track. Expect a cooler day across
the CWA on Sunday, even though it will be windy over North Central
MT on Sunday afternoon. Brusda

&&

.DISCUSSION...
/Issued 801 PM MDT Sat Aug 29 2026/

 - Meteorological Overview:

A deep upper level low moving into the Pacific Northwest will
continue to funnel moisture into North Central and Southwestern
Montana today on southwesterly flow aloft. Early afternoon radar
has shown numerous showers and thunderstorms developing across
Southwestern Montana, with a few also developing over the Rocky
Mountain Front and Little Belt and Snowy Mountains. While severe
wind gusts are not expected today, I cant entirely rule out a
stronger storm producing a rogue gust over 50 mph or so, along
with some heavier downpours, especially if they can get a bit more
organized. The most likely area for the winds to get gusty will
be across the plains, where clouds will hold off just long enough
to allow for some better thermal mixing and deepening of the mixed
layer. While storms should weaken after sunset, showers with a
few rumbles of thunder will remain possible through much of the
overnight thanks to persistently strong upper level dynamics.

As we head into the day on Sunday, winds shift to the west as the
upper level low moves overhead, which will bring a surface cold
front along with it late tonight/early Sunday morning. Behind this
front, expect temperatures to be notably cooler tomorrow, with
most locations only rising into the 60s, along with a breezy
westerly wind with most areas on the plains gusting to 25-40 mph
and 15-30 mph across the southwest.

While it will remain breezy on the plains/Rocky Mountain Front
overnight Sunday night into Monday morning, expect more pleasant
conditions to arrive for the daytime on Monday as upper level
ridging begins to build back across the Northern Rockies. While
this ridge will keep us dry on Monday, it will quickly move east
as a strong trough moves towards the West Coast. As this trough
approaches, southwesterly flow aloft will bring a surge of
moisture into the area, resulting in afternoon thunderstorm
development Tuesday and Wednesday. A stronger upper level low will
likely move towards the Pacific Northwest late next week, which
would allow for additional showers and thunderstorms Thursday and
Friday.

 - Forecast Confidence & Scenarios:

Rain today: Some of the convection allowing models have wanted to
have some pockets of heavier rainfall (up to an inch) from some
of the showers and thunderstorms today. While our soils should be
able to readily absorb these heavier rainfall amounts, repeated
heavy rainfall may result in some ponding of water in poor
drainage areas.

Winds Sunday: Behind the cold front mentioned above, expect gusty
winds to affect most of North Central and Southwestern Montana on
Sunday. While cooler temperatures, recent rainfall, and RH values
generally staying above 25-30% will prevent critical fire weather
conditions, wind gusts will still be notable for late August.
Expect an 80-90% chance of seeing wind gusts over 40 mph along the
Rocky Mountain Front, northern slopes of the Little Belt and
Snowy Mountains, and around the Bears Paw Mountains, and a 30-60%
chance of seeing gusts over 48 mph. While not impossible, the risk
of seeing high wind gusts (over 58 mph) appears to be low,
generally under 10-20%, I can not completely rule out an isolated
instance of high winds tomorrow. Ludwig

&&

.AVIATION...
30/06Z TAF Period

Showers and thunderstorms will linger throughout the majority of
the CWA during the first few hours of this TAF period, beginning
to dissipate around 14Z. Westerly winds will increase in the late
morning/early afternoon, with most terminals seeing gusts between
25-30 kts. KGTF, KCTB and KHVR will see gusts around 35-40 kts.
These winds will last into the evening, before beginning to
dissipate around 01Z. VFR conditions will prevail throughout this
TAF period, with MVFR conditions and mountain obscuration
possible due to a passing shower or thunderstorm.

For KGTF: Thunderstorms will continue to impact KGTF through 09Z,
before transitioning to light rain showers. The rain showers will
dissipate and southwesterly winds will begin to increase around
14Z, with a sustained wind around 20 kts and gusts around 35 kts.
The winds will last into the evening, beginning to dissipate
around 01Z. Due to the southwesterly component of these winds,
there is a less than 10% chance of a cross-wind exceeding 15 kts
outside of a thunderstorm. -Dzomba


&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  50  65  45  77 /  70  30   0   0
CTB  46  61  44  74 /  60  20  10   0
HLN  46  67  43  78 /  80  30   0   0
BZN  47  67  39  78 /  70  70   0   0
WYS  36  62  30  71 /  90  70   0   0
DLN  44  69  38  79 /  70  30   0   0
HVR  51  68  47  77 /  80  50  10   0
LWT  47  64  42  77 /  80  70   0   0

&&

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

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