972
FXUS65 KTFX 011654
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1054 AM MDT Fri Aug 1 2025

Aviation Section Updated.

.KEY MESSAGES...

- Mostly afternoon and evening scattered showers and
  thunderstorms are expected today and Saturday, with some of the
  stronger storms capable of localized flooding, especially over
  urban areas and other flood susceptible areas of Central and
  North-central Montana.

- Additional daily rounds of showers and thunderstorms continue
  through the weekend into early next week, but the threat for
  flooding diminishes.

&&

.UPDATE...
/Issued 829 AM MDT Fri Aug 1 2025/

Today there will be more rounds of showers and thunderstorms with
thunderstorms producing heavy rainfall, gusty winds, and small
hail. Showers and thunderstorms will exit Hill and Blaine County
over the next couple of hours. For the update, PoPs across a
portion of the Hi-line were increased for the next couple of
hours to reflect the latest hi-res model guidance and current
radar imagery. PoPs in Southwestern Montana early this afternoon
were increased to reflect the latest hi-res model guidance.
Temperatures across the plains were increased to reflect current
observations and trends. The rest of the forecast is on track. -IG

&&

.DISCUSSION...
/Issued 829 AM MDT Fri Aug 1 2025/

 - Meteorological Overview:

A weak, but moist and unstable southwesterly flow will remain
over the Northern Rockies today. lingering showers and
thunderstorms from yesterday continue to produce heavy rainfall
and frequent lightning over Blaine County this morning. This
activity will slowly diminish through mid morning, but another
shortwave looks to send another wave of northward moving storms
later this afternoon through the early overnight hours. Excessive
moisture with PWATS well over an inch over Central and North-
central Montana combined with slow storm motion will once again
increase the risk for localized torrential downpours and flash
flooding concerns, particularly for urban areas, burn scars, and
other normally flood prone areas. Given CAPE levels creeping up to
and above 1,500 J/kg, the stronger cells may also contain hail,
and gusty winds over 40 mph.

Similar conditions are expected again on Saturday, although CAPE
levels look to fall from the 1,500 to 2,000 J/kg level to around
1,000 J/kg and less. Additionally, a mid- level low looks to
develop over the Canadian prairies may start to bring in slightly
drier air. Regardless, there`s an expectation for at least general
thunderstorms capable of localized heavy rain, gusty winds, and
hail in addition to lightning.

The aforementioned mid-level low will take the richest moisture
eastward with it, dropping PWATS below the one inch mark by the
afternoon hours. Most of the thunderstorm activity should be
confined to along the Hi-Line and to areas east of a Great Falls
to Havre line. A more progressive southwesterly flow aloft moves
in for next week. There will still be daily rounds of showers and
thunderstorms, but faster storm motion and slightly drier
atmospheric conditions will reduce the risk for flooding. The most
active day looks to be on Monday when a fast moving shortwave
swings into the Northern Rockies and brings a quick round of
showers and thunderstorms, some of which may be on the strong to
severe side. - RCG

 - Forecast Confidence & Scenarios:

localized torrential downpours and flash flooding potential today
and on Saturday...

Another shortwave moves in from the southwest and will interact with
high instability and excessively high moisture levels. PWATS between
an inch and inch and a half combined with CAPE above 1,500 J/kg over
Central and North-central Montana will cause some of the northward
moving storms from Southwest Montana to become strong to severe.
While the scattered nature of the storms will prevent widespread
flash flooding, those that happen to spend time under these storms
may receive rainfall rates up to and over an inch per hour. This
will especially be impactful to the more flood susceptible areas,
including urban centers, burn scars, and low lying areas. Given
these factors and the heavy rains from previous days, a flood
watch was issued for much of Central and North-central Montana.

High moisture and slow storm motion continue on Saturday, but lower
CAPE may reduce the coverage of stronger storms. Then a more
progressive pattern will bring faster storm motion and slightly
drier profiles Sunday into next week. Monday looks to be the day
with the most widespread and strongest activity, but this will
ultimately depend on the timing of the responsible shortwave.
- RCG

&&

.AVIATION...
01/18Z TAF Period

Rain, with embedded thunderstorms, will continue to pivot around a
MCV over Northern Hill and Blaine Counties through 18-22z this
afternoon, with generally broken VFR conditions expected at the
KHVR terminal. Additional showers and thunderstorms are then
expected to develop, initially over the higher terrain of the
Continental Divide and Southwest Montana between 18-20z this
afternoon, with these showers and thunderstorms then lifting to
the northeast at 15-25kts. While VFR conditions will largely
prevail throughout the 0181/0218 TAF period heavy rain beneath
shower and thunderstorm activity, most notably north of a KHLN to
KLWT line, will periodically reduce VIS and/or CIGS to MVFR/IFR
conditions. Widespread mountain obscuration is not expected;
however, localized obscuration is likely near/beneath
precipitation. - Moldan

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

&&

.HYDROLOGY...

...Localized flash flooding potential over portions of Central
and North- central Montana this afternoon and tonight...

Another shortwave moves in from the southwest and bring locally
heavy showers and thunderstorms to Central and North-central
Montana this afternoon and tonight. While the scattered nature of
the storms will prevent widespread flash flooding, areas that
happen to spend time under these storms may observe rainfall rates
up to and over an inch per hour. This will especially be
impactful to the more flood susceptible areas, including urban
centers, burn scars, and low lying areas. Given these factors and
the heavy rains from previous days, a flood watch was issued for
much of Central and North- central Montana north of the highway 12
corridor, excluding the Northern Rocky Mountain Front and Hi-
Line locations going eastward to the Sweet Grass Hills. High
moisture and slow storm motion continue on Saturday, but lower
instability may reduce the coverage of stronger storms.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  85  58  80  57 /  70  80  40  20
CTB  80  57  74  56 /  80  70  50  30
HLN  83  58  81  56 /  70  50  40  20
BZN  86  52  83  50 /  40  30  30  20
WYS  77  40  77  39 /  30  10  40  30
DLN  79  48  79  47 /  60  20  30  20
HVR  87  60  82  59 /  60  90  50  40
LWT  83  53  77  52 /  60  80  50  30

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Flood Watch from 2 PM MDT this afternoon through late tonight
for Bears Paw Mountains and Southern Blaine-Big Belt, Bridger
and Castle Mountains-Cascade County below 5000ft-Eastern Pondera
and Eastern Teton-Fergus County below 4500ft-Gates of the
Mountains-Helena Valley-Hill County-Judith Basin County and
Judith Gap-Little Belt and Highwood Mountains-Northern Blaine
County-Snowy and Judith Mountains-Southern High Plains-Southern
Rocky Mountain Front-Upper Blackfoot and MacDonald Pass-Western
and Central Chouteau County.

&&

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