987
FXUS65 KTFX 242251
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
451 PM MDT Sun Aug 24 2025

Aviation Section Updated.

.KEY MESSAGES...

 - Temperatures will gradually warm up today through Tuesday, with
   temperatures slightly cooling down Wednesday through Friday.

 - Showers and thunderstorms will return to Southwest Montana
   starting tomorrow and last through the rest of the work week.

 - Wildfire smoke will continue to impact the air quality in
   locations near active fires.

&&

.DISCUSSION...
/Issued 304 PM MDT Sun Aug 24 2025/

 - Meteorological Overview:

Over the next few days upper level ridging will move to the east
enough to allow monsoonal moisture to make its way into southern
Montana. The result of this will be daily chances for showers and
thunderstorms across southwest Montana and, to a lesser extent,
central Montana. Wildfire smoke will continue to impact locations
and valleys surrounding active fires with periods of reduced air
quality possible.


 - Forecast Confidence & Scenarios:

The greatest concerns for thunderstorms this week will be across
southwest Montana. Drier and more isolated thunderstorms are
expected on Monday and Tuesday south of I-90. The main concerns
will be gusty outflow winds which will increase fire weather
concerns, especially near active wildfires.

Shower and thunderstorm coverage will become more widespread
Wednesday through Friday with additional moisture allowing for
wetter thunderstorms and heavy downpours across southwest Montana
into portions of central Montana. Exactly far north these showers
go is still a bit of an unknown but locations south of Hwy 200
are likely to see at least some rain over the next week.

One of the wild cards with this event is how much CAPE is present
each day. Right now model values are relatively low which suggests
more of a stratiform event and less of a convective event.
However, should CAPE values start to increase with future model
runs then convective weather starts becoming a much greater
threat. In particular, the potential for heavy downpours will
increase which may turn into a flash flood concern (see
HYDROLOGY).

As of now, there is still a bit of uncertainty with regards to
exactly how this event will play out. But the main things to watch
will be increased fire weather concerns at the start of the
event transitioning into more of a flood concern towards the
middle and end of the event. Things are likely to change so the
best advice now is to stay tuned for future updates and model
runs to resolve the finer details. -thor


&&

.AVIATION...
25/00Z TAF Period.

VFR conditions are generally expected for this TAF period under
passing mid- high level cloudiness. Afternoon instability will
initiate some cloud builds and perhaps an isolated shower or
storm over the higher terrain of far Southwest Montana through
25/04Z. A better chance for isolated showers and thunderstorms is
expected for southwestern locations south of I90 Monday afternoon
and evening. Also, smoke and haze from area wildfires may cause
compromised slantwise visibility and occasional scattered to
broken low VFR ceilings. The trend for east to northeasterly
surface breezes will continue. - RCG

Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.

&&

.HYDROLOGY...

The main timeframe of concern is Wednesday through Friday with the
highest concerns for excessive rainfall south of I-90. Currently
the NAEFS mean PWAT values are sitting at 3 to 4 standard
deviations above normal across southwest Montana meaning that the
expected moisture will be well above normal and, should it all
precipitate out, it will be a flood concern. These concerns are
amplified around the recent burn scars in southwest Montana which
will be more susceptible to flash flooding and debris flows.

For right now, it is too early to pin point the exact extent of
the flood threat so no products will be issued with this forecast.
However, this will be something to watch with future updates. -thor


&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  50  86  53  86 /   0   0   0   0
CTB  47  84  50  84 /   0   0   0   0
HLN  53  87  55  87 /   0   0   0  10
BZN  47  87  49  86 /   0   0   0  20
WYS  39  81  43  72 /   0  10  30  70
DLN  49  84  52  80 /   0   0  10  50
HVR  48  85  50  87 /   0   0   0   0
LWT  48  81  48  81 /   0   0   0   0

&&

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

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