552
FXUS65 KTFX 181002
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
402 AM MDT Sat Jul 18 2026

.KEY MESSAGES...

- Another round of scattered showers and thunderstorms will move
  in a southwest to northeast fashion this afternoon and tonight,
  mostly impacting southwest MT and north-central areas east of
  I15.

- Thunderstorm hazards will include strong, gusty winds, hail,
  and heavy downpours capable of producing isolated instances of
  localized flooding.

- Sunday will be breezy and dry with continued very warm to hot
  temperatures.

- After a brief cooldown Monday, summer heat and daily rounds
  of storms return heading towards the middle of next week.

&&

.DISCUSSION...

Lingering shower and thunderstorm activity from last night has
mostly diminished and ended while some patchy areas of low stratus
and fog develop over portions of central and southwest MT this
morning. This should clear out by mid- morning with the focus
turning to another shortwave passing through an unstable
southwesterly flow aloft and bringing another round of scattered
showers thunderstorms this afternoon and evening. Similar to
yesterday, this activity will initialize over west and
southwestern MT early in the afternoon before moving northeastward
over the plains and valleys later in the afternoon and evening.

Model guidance has ramped up today`s ML CAPE values to around 800
to 1,500 J/kg, resulting in more widespread convective activity
than what was anticipate 24 hours ago, especially for southwest MT
and for central/north-central areas east of I15. Drier surface
conditions suggest that instances of localized strong wind gusts
over 60 mph will be more pronounced while shear above 25 kts will
be marginally supportive of hail events. These storms will also be
capable of producing isolated flooding of sensitive burn scars
and urban areas, although PWATS look to drop off some compered to
the last few days. Given slightly lower moisture levels and more
progressive storm motion, I decided to hold off on flash flood
products for now.

Today`s showers and storms should wind down by late this evening
with increased westerly flow aloft bringing drier, breezy, and
continued hot conditions on Sunday. Deep layer mixing and H700
flow approaching 30 to 35 kts will keep the windiest conditions
along the Rocky Mountain Front and the plains. Any shower or
thunderstorm activity will be isolated and mostly confined to the
higher terrain of southwest MT. A Canadian surface front will
bring a northerly wind shift and a brief cooldown on Monday before
ridging aloft strengthens and brings a return to hot conditions
heading towards the middle of next week. Passing shortwaves
interacting with monsoon moisture will also increase daily shower
and thunderstorm activity. - RCG

&&

.AVIATION...
18/06Z TAF Period

Showers and thunderstorms over north-central and southwest MT
will slowly diminish in coverage as they move northeastward
during the overnight hours. Gusty winds in excess of 25 kts,
lightning, and brief low VFR/MVFR conditions will be the primary
impact through around 18/10Z. Patchy fog development will be
present over the wind protected river valleys between 18/09 and
18/15Z, especially areas that received rainfall Friday afternoon
and evening. Another shortwave moves in from the southwest and
brings additional scattered showers and storms moving in a
southwest to northeast fashion by 18/20Z. This activity will be
most widespread over southwest MT and central/north-central areas
east of I15. Strong gusty winds will be the primary impact, but
some storms will have hail and downpours as well. - RCG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  95  61  95  59 /  30  30   0   0
CTB  91  57  87  55 /  20  20   0   0
HLN  93  61  94  59 /  40  50  10   0
BZN  92  57  93  56 /  30  30  10  10
WYS  87  48  86  48 /  20  20   0   0
DLN  89  55  90  55 /  30  30   0   0
HVR  97  63  95  58 /  30  30   0   0
LWT  89  57  90  54 /  30  40  20  10

&&

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

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