341
FXUS65 KTFX 151850
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1250 PM MDT Sat Aug 15 2026

.KEY MESSAGES...

- A few storms may produce localized strong, gusty winds and
  even some instances instances of brief downpours capable of
  localized flooding, mostly over central and southwest Montana.

- Some patchy fog will develop again by early Sunday morning,
  mostly for the southwest valleys and the river valleys over the
  plains.

- Daily rounds of showers and thunderstorms will continue
  through mid- week, most widespread Monday evening through early
  Tuesday.

- Seasonable temperatures will climb back above average towards
  the end of next week with shower and thunderstorm activity
  increasing once again next weekend.

&&

.DISCUSSION...

 - Meteorological Overview:

A moist southwesterly flow aloft will become more westerly and
undergo some drying heading into early next week. This drying will
bring increased breeziness and lowering minimum relative humidity
values. Daily scattered shower and thunderstorm activity will
continue through mid-week, most widespread during a shortwave
passage late Monday into Tuesday.

Ridging aloft strengthens over the Great Basin with heights
rising as high as the 588 to 594 dm range over the Northern
Rockies by Friday. This will reduce shower and storm coverage and
push afternoon temperatures back to the upper 80s to near 90 while
seasonal breeziness continues.

A Pacific trough approaches the region sometime next weekend and
brings increased shower and thunderstorm activity with the warmest
temperatures of week looking to occur just ahead of this system.
This will be followed by breezy to windy conditions and slightly
cooler temperatures. - RCG

 - Forecast Confidence & Scenarios:

Daily rounds of showers and thunderstorms through Tuesday...

Scattered showers and thunderstorms are already developing over S
ID with W MT not far behind. This activity will move toward the
northeast into central and southwest MT and interact with peak ML
CAPE generally running between 500 and 1000 J/kg and effective
shear above 20 kts. With surfaces beginning to dry out, localized
strong, gusty winds, lightning, and perhaps some small hail will
be the primary hazards, but PWATS as high as 0.80 inches may bring
some heavier downpours capable of localized flooding,
particularly for the more sensitive burn scars. No flood products
are planned for today given the isolated nature of the heavier
downpours, but conditions will be closely monitored through the
evening hours. Showers and storms will weaken in coverage and
intensity as they move northward into north-central MT later this
evening into the overnight hours.

Westerly flow aloft will begin to thin the moisture profile
Sunday and Monday, but will maintain at least similar shear and
instability for continued scattered shower and thunderstorm
activity. Dryer sub- cloud layers will increase instances of
strong to severe wind gusts while decreasing the localized
flooding threat. All locations will be subjective stronger storms,
although southwest MT and areas along the Hi-line will be most
susceptible. Showers and storms will be most widespread during a
shortwave passage late Monday into Tuesday, although the timing of
the trough and attendant cold front will determine whether this
activity will be able to take advantage of the peak diurnal
instability for stronger storm initiation. - RCG

&&

.AVIATION...
15/18Z TAF Period

Low CIGS over the plains and valleys of Central and North Central
Montana will continue to slowly lift through 21z this afternoon,
with otherwise low-VFR/VFR CIGS expected through 03-09z Sunday
before CIGS lower once again and patchy fog develops over
portions of Southwest through North Central Montana. Showers and
thunderstorms will develop through 21z this afternoon across
Northeast Idaho and Southwest Montana before lifting northeast
across the remainder of Southwest and portions of Central Montana.
Main threat from these storms will be strong winds gusts and the
potential for heavy rainfall.

For KGTF: Light surface winds through the duration of the TAF
period will yield a low risk of crosswinds exceeding a 15 kt
crosswind; however, thunderstorms lifting northeast into Central
Montana from 02z-06z have the potential to produce outflow
boundaries that could briefly exceed the 15kt threshold. The
probability for these thunderstorms is around a 30% chance. -
Moldan

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  77  51  83  52 /   0  20  30  30
CTB  71  46  77  47 /   0  10  20  20
HLN  78  50  82  53 /  20  80  20  30
BZN  77  47  79  48 /  20  60  30  40
WYS  72  34  75  35 /  50  80  20  20
DLN  74  44  77  46 /  70  70  30  30
HVR  76  49  84  50 /   0  30  20  30
LWT  73  48  79  49 /  30  50  30  30

&&

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

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