275
FXUS65 KTFX 141109
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
509 AM MDT Fri Aug 14 2026

Aviation Section Updated.

.KEY MESSAGES...

 - Another cooler day with showers and thunderstorms.

 - Some thunderstorms will be capable of heavy rain today.

 - Trending warmer this weekend, though afternoon and evening
   showers and thunderstorms will remain.

&&

.DISCUSSION...
/Issued 1239 AM MDT Fri Aug 14 2026/

 - Meteorological Overview:

A southwesterly flow aloft will persist across the region over the
upcoming week. This flow aloft is initially cyclonic in nature,
which will aid in lots of showers and thunderstorms, even during the
overnight, through tonight. Precipitable water values are still
somewhat elevated, which will allow for a few stronger thunderstorms
to produce heavy rainfall rates, at least briefly. Should one of
these stronger thunderstorms move over an urban area or a burn scar,
there would be flash flooding concerns.

Heading into the weekend the southwesterly flow becomes more
anticyclonic in nature, with rising heights aloft. Typically this
would suppress convection somewhat, but given the forecast lingering
moisture near the surface across Southwest and Central Montana and
rising temperatures, another round of showers and thunderstorms
looks to develop Saturday afternoon and evening. Precipitable water
looks to decrease at least somewhat, which would favor a lower
probability for excessive rainfall.

The same story plays out Sunday, though with another day of drying,
overall coverage of showers and thunderstorms becomes more
questionable. Continued southwest flow aloft with a few embedded
waves will foster additional round of scattered showers and
thunderstorms into early next week as temperatures trend to near
average. Confidence in specifics wanes after Tuesday, though the
main takeaway continues to be for additional scattered showers and
thunderstorms. -AM

 - Forecast Confidence & Scenarios:

Flooding risk today:

Precipitable water values fall ever so slightly today, but still
look to be high enough to result in some heavier rainfall rates.
Storm motions look to be slightly faster, which also would favor
lesser of a risk for excessive rainfall leading to flash flooding.
Given the threshold for flash flooding is so low over the active
fires in the Pioneers, and that they have already received a wetting
rain over the previous 24 hours, another flash flood watch was
issued from 1 pm to 9 pm for today. A few high resolution members
take a shower or thunderstorm through this area early this morning,
but the probability of this occurring is too low to warrant having
the watch begin early this morning. Trends will continue to be
monitored for changes in confidence in this area this morning.

As of now the concern level at Horse Gulch Burn Scar is slightly
lower. Should this concern level rise even slightly, an additional
flash flood watch would become necessary. -AM


&&

.AVIATION...
14/12Z TAF Period

VFR conditions will prevail across the KEKS and KWYS terminals
during this TAF Period. During this TAF Period at the KBZN, KGTF,
KCTB, and KLWT terminals ceilings will lower to at least IFR-levels.
During this TAF Period there will be showers and thunderstorms
across North-central, Central, and Southwestern Montana. During the
duration of this TAF Period there will be mountain obscuration
across North-central, Central, and Southwestern Montana. -IG


For KGTF: Light winds are forecast this TAF period, which will yield
a nearly zero probability of a 15 kt crosswind. Aside from the
low clouds and intermittent showers or isolated thunderstorm, the
main concern will be for icing. Most forecast soundings feature at
least at shallow layer of clouds in the 0C to -15C range through
the early afternoon today. -IG/AM

&&

.HYDROLOGY...

Precipitable water values fall ever so slightly Friday, but still
look to be high enough to result in some heavier rainfall rates.
Storm motions look to be slightly faster, which also would favor
lesser of a risk for excessive rainfall leading to flash flooding.
Given the threshold for flash flooding is so low over the active
fires in the Pioneers, and that they have already received a
wetting rain over the previous 24 hours, another flash flood watch
was issued from 1 pm to 9 pm for today. HREF probabilities for a
quarter inch of rain over an hour in the neighborhood of the
active fires is roughly 50%. This gave enough confidence to
warrant the flash flood watch. Trends will continue to be
monitored further north for the Horse Gulch Burn Scar for an
additional flash flood watch.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  66  50  76  50 /  60  40   0  20
CTB  59  44  71  45 /  50  20   0  10
HLN  70  50  77  51 /  60  50  20  40
BZN  73  47  75  46 /  60  60  30  40
WYS  66  35  70  34 /  60  60  60  60
DLN  72  45  73  44 /  70  50  50  50
HVR  68  48  76  48 /  50  30  10  20
LWT  65  47  72  48 /  70  40  40  40

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch from 1 PM MDT this afternoon through this
evening for Northwest Beaverhead County.

&&

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