100
FXUS65 KTFX 210249
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
849 PM MDT Mon Jul 20 2026

.KEY MESSAGES...

 - Trending warmer through the week, with Friday into the weekend
   looking hottest.

 - Slow moving storms across Southwest Montana Wednesday afternoon
   and evening will result in an increased risk for excessive
   rainfall leading to flash flooding.

 - Additional showers and thunderstorms elsewhere Wednesday and
   Thursday ahead of a drying trend Friday into the weekend.

&&

.UPDATE...

Not much change from the previous forecast, but smoke will remain
a bit more persistent than the previous forecast had. Smoke has
been expanded through the overnight. Ludwig

&&

.DISCUSSION...
/Issued 548 PM MDT Mon Jul 20 2026/

 - Meteorological Overview:

Upper level ridging centered over the central and southern US with
axis stretched northwestward toward the Northern Rockies will
generally be the pattern that persists through much of the upcoming
week across the region. The ridge is in its initial stages of
rebuilding, with a drier zonal flow aloft still persisting across
the region. This overall drier setup, along with cooler surface
temperatures behind a cold front will inhibit shower or thunderstorm
development through the remainder of the day and into tonight.
Wildfire smoke will be around at times through much of the
upcoming week.

Monsoonal moisture will begin to move northward through the western
periphery of this upper level ridging as a more southerly or
southwesterly flow aloft develops Tuesday onward. Afternoon and
evening showers and thunderstorms initially look to remain confined
to areas across Southwest Montana before spreading further north
Wednesday and Thursday. Anomalous moisture associated with the
monsoonal push combining with weak winds aloft look to result in
slower storm motions by Wednesday, particularly across Southwest
Montana. This will yield an increased risk for excessive rainfall
which leads to flash flooding. Those in urban areas or near burn
scars or steep terrain should be aware of this increased risk for
excessive rainfall Wednesday.

Storm motions look to increase slightly for Thursday, though still
remain on the slower side. At this point confidence is highest in
Wednesday being the day with the greatest risk for excessive
rainfall, with Southwest Montana being the area of greatest concern.

The risk for severe weather Wednesday and Thursday looks to be more
favorable further north on the plains, where forecast soundings show
slightly deeper inverted-V soundings. The lack of a stronger forcing
mechanism raises concerns as to how widespread shower and
thunderstorm development will be on the plains, but should it occur
the risk for strong wind gusts would certainly exist.

By Friday the most robust monsoonal moisture begins to be shunted
further south and east again as a drier zonal flow develops
across the region. Lingering moisture looks sufficient to result
in another round of afternoon showers and thunderstorms Friday,
though coverage looks lower at this point and the risk for
excessive rainfall looks to decrease significantly. What this does
mean however is that gusty westerly winds will begin to work back
as temperatures continue to trend hotter Friday. As of now the
better monsoonal moisture looks to remain south of the region this
weekend, which would keep things on the hotter and drier side.
Those with outdoor plans this weekend should plan for plenty of
breaks and to hydrate often to help mitigate concerns from the
heat. Areas that see little precipitation this week will have
increased concern for fire weather this weekend given forecast
hot, dry, and breezy conditions. -AM

 - Forecast Confidence & Scenarios:

The main source of uncertainty at this point looks to occur on
Wednesday and Thursday, associated with the risk for excessive
rainfall in southern areas and potential for strong to severe
thunderstorms in northern areas. Where this transition in threat
occurs will largely be dictated by where the `strongest` flow
aloft resides. Should this stronger flow aloft trend northward,
the risk for excessive rainfall leading to flash flooding would
edge northward and vice versa. It should be noted that excessive
rainfall leading to flash flooding will be a concern in urban
areas and burn scars, regardless of where the strongest flow aloft
ends up settling. -AM

&&

.AVIATION...
21/00Z TAF Period

Isolated showers will continue across portions of Central and
Southwest Montana through the evening. Temporary reductions to
low-VFR and mountain obscuration is possible but there is low
confidence in any one shower impacting any of the terminals. Hazy
skies will continue through the rest of the evening and, while
impacts at surface level are generally not expected, there will be
some reduced slantwise visibility upon ascent/descent that will
continue at least through tonight. A BKN to OVC mid-level cloud
deck will start to fill in overnight and persist through much of
the TAF period. Another round of isolated showers and
thunderstorms are possible Tuesday afternoon along the Continental
Divide and south of the I-90 corridor but confidence in location
and timing still remains too low to include it in the TAF.  -thor

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  60  85  60  90 /  10  10  10   0
CTB  56  80  56  87 /   0  10  10   0
HLN  60  87  62  90 /   0  10  10  30
BZN  57  88  58  90 /   0  10  10  40
WYS  50  87  51  82 /   0  30  30  90
DLN  55  84  56  85 /   0  20  20  60
HVR  58  85  60  94 /   0  10  10  10
LWT  54  82  55  86 /   0  10  10  20

&&

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

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