413
FXUS65 KTFX 240002
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
602 PM MDT Sun Aug 23 2026

Aviation Section Updated.

.KEY MESSAGES...

 - Scattered thunderstorms this afternoon capable of strong wind gusts
   up to 80 mph and marginally large hail, mainly east of I-15
   ahead of a cold front.

 - Gusty winds behind a cold front this afternoon, with elevated
   fire weather conditions.

 - Generally near or above average temperatures this week with a few
   days of scattered showers and thunderstorms.

&&

.DISCUSSION...
/Issued 1236 PM MDT Sun Aug 23 2026/

 - Meteorological Overview:

Potent upper level troughing moving across the region today will
bring an array of impacts, including strong to severe thunderstorms
and elevated fire weather conditions. A cold front will be moving
through today, which will delineate the transition between a more
thunderstorm focused risk and fire weather risk.

Ahead of the cold front ample moisture looks to coincide with
daytime heating and forcing from the passing upper level disturbance
to result in scattered showers and thunderstorms, mainly east of I-
15. Deep mixing and shear on the order of 30-40kts will support the
risk for large hail with initial storms before the risk transitions
to be more wind focused. Latest mesoanalysis features DCAPE in
excess of 1200 J/Kg over the plains, which would support the risk
for wind gusts approaching 80 mph in the strongest thunderstorms
that form. While PWATs are still elevated, the deep inverted-V
profiles will support a mix of wet and dry thunderstorms.

Behind the cold front a period of breezy west winds is forecast to
develop in most areas. The lowest portion of the atmosphere dries
out quite quickly behind the front, which will allow for relative
humidity to continue falling behind the front, even as temperatures
cool. The combination of the breezy and dry conditions, as well as
the potential for a few dry thunderstorms brings about an elevated
fire weather risk across most of the region.

Heading into Monday the upper system responsible for active weather
today will exit eastward. Weak ridging builds in across the west in
wake of this system, though with some lingering monsoonal moisture
near the Idaho border between Monida and West Yellowstone, a few
thunderstorms cannot be ruled out by late afternoon. The rest of the
region looks dry Monday.

The upper level ridging more or less persists much of the upcoming
week, but as it shifts slowly eastward an upper level trough
approaching the Pacific NW will slowly allow for showers and
thunderstorms to spread further and further northward across the
region each day. -AM

 - Forecast Confidence & Scenarios:

The main source of uncertainty today is with respect to how ongoing
convection over the plains north of Great Falls will modify the
convective environment this afternoon. On one hand this activity may
limit destabilization in some areas where forcing is greatest.
Conversely this activity and associated outflow may serve as a focus
for additional convective initiation mid-afternoon, resulting in
perhaps a greater areal extent of convective activity.
ADditionally, if this activity persists, it could eventually break
the cap and intensify and become the main area of concern across
the Hi-Line. Nonetheless, any thunderstorm that forms this
afternoon will be capable of strong wind gusts, and at least
briefly large hail. -AM

&&

.AVIATION...
24/00Z TAF Period

Aside from a few lingering SHRA and TSRA south and east of KBZN
and KEKS, expect largely VFR conditions to persist across North
Central and Southwestern Montana. While gusty westerly winds will
persist through the remainder of the evening, winds should
dissipate overnight tonight. Winds increase again again Monday
afternoon, particularly north and east of KLWT and KCTB.

For KGTF: Westerly winds will diminish over the next few hours and
into the overnight hours. Expect generally light winds Monday with
gusts generally under 15kts, initially from the southwest after
sunrise before shifting to northwest after 18z. While crosswinds
are likely in the afternoon, the risk of seeing crosswinds over 15
kts is under 10%. Ludwig

&&

.FIRE WEATHER...

A surface front will bring gusty westerly winds through the
afternoon hours across the region. Widespread gusts over 35 mph
are possible and will be enhanced by any thunderstorm activity
that develops. Minimum RH values will be most critical in
Southwest Montana where the RFW is currently in effect for Sunday
afternoon and evening. Further north, conditions will be windy but
not quite as dry. Additionally there is some disagreement in the
latest models as to how the thunderstorms will develop and how
widespread they will be. With this uncertainty in place the
decision was made to hold off on issuing a RFW for North-Central
Montana for now. But elevated to near-critical fire weather
conditions will be a concern across the entire region. Where
thunderstorms do develop, the concerns will be frequent lightning
and gusty/erratic winds which may lead to new fire starts and make
new and/or existing fires difficult to contain.  -thor

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  54  81  53  83 /   0   0   0   0
CTB  50  77  48  79 /   0   0   0   0
HLN  50  84  52  85 /   0   0   0   0
BZN  48  82  49  84 /  10   0   0  20
WYS  39  79  41  79 /  20   0  20  20
DLN  47  84  50  85 /   0   0   0  20
HVR  55  82  51  84 /  10   0   0   0
LWT  52  79  48  82 /  30   0   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
&&

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