Severe Thunderstorm Warning 164, NWS Great Falls, MT

Area Forecast Discussion
National Weather Service Great Falls MT
547 PM MDT Sun Sep 14 2025

Aviation Section Updated.

.KEY MESSAGES...

 - Showers and thunderstorms will affect Southwestern Montana this
   afternoon through this evening.

 - Tonight through Tuesday there will be widespread showers and thunderstorms.

 - It will be warm today with temperatures cooling down through
   the middle of the week.

&&

.DISCUSSION...
 - Meteorological Overview:

This afternoon there is a weak upper-level shortwave over North-
central, Central, and Southwestern Montana before an upper-level
trough associated with a surface cold front begins to move over the
area this evening. Until this evening across North-central, Central,
and Southwestern Montana it will be warm and mostly dry. Late
this afternoon through this evening isolated showers and
thunderstorms will affect Southwestern Montana. Showers will
increase in coverage across North-central, Central, and
Southwestern Montana tonight. On Monday the upper-level trough
remains over the area. This combined with the surface cold front
will cool temperatures down to slightly below seasonal averages
on Monday. On Monday there will be widespread showers across
North-central, Central, and Southwestern Montana. Monday
afternoon and evening there will also be isolated thunderstorms
across the area.

On Tuesday the upper-level trough remains over North-central,
Central, and Southwestern Montana. This will bring showers to the
area with about seasonal averages for temperatures. The showers will
move out of North-central, Central, and Southwestern Montana by
Tuesday evening. On Wednesday an upper-level ridge builds in over
North-central, Central, and Southwestern Montana. This will bring
dry weather with temperatures warming up across the area. On
Thursday the upper-level ridge remains over North-central, Central
and Southwestern Montana which will keep the dry and warm weather
for the area on Thursday. Friday through Saturday an upper-level
trough will move over North-central, Central, and Southwestern
Montana which will bring cooler temperatures and precipitation
chances to the area. -IG

 - Forecast Confidence & Scenarios:

On Monday there is a 15 - 30% chance for thunderstorms across North-
central Montana and a 25 - 45% chance for thunderstorms in
Central and Southwestern Montana with the highest probabilities in
Southwestern Montana. On Tuesday there is a 15 - 30% chance for
thunderstorms in Judith Basin, Fergus, Meagher, and Gallatin
Counties. On Monday there is a 20 - 50% chance for a quarter inch
of rain across North-central, Central, and Southwestern Montana
along and south of a Cut Bank to Lewistown line. On Tuesday there
is a 20 - 50% chance for a quarter inch of rain across North-
central, Central, and Southwestern Montana south of the Hi-Line
east of I-15. -IG

The Friday into the weekend timeframe is where the greatest
uncertainty lies. The difference between reasonable low-end and high-
end (10th to 90th percentile) high temperatures Friday and Saturday
is more than 20 degrees in many locations. Weaker/non-existant
troughing would favor the warmer solution, while a more robust, non
splitting trough would favor the cooler scenario. -AM

&&

.AVIATION...
15/00Z TAF Period.

Main concern will be showers/thunderstorms this evening over the
western portions of the CWA. The storms will generally stay west
of a Great Falls to Bozeman line. Some storms will produce strong
wind gusts. Expect scattered storms after 06z, with showers
developing towards 12z over Southwest MT. The showers will
continue over Southwest MT, including the West Yellowstone area
all day on Monday. Mountains/passes will be obscured at times
through the period, especially over Southwest MT. Brusda

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  52  72  52  73 /  40  40  70  20
CTB  51  67  49  73 /  20  50  40  10
HLN  51  69  50  73 /  50  60  50  30
BZN  45  68  45  68 /  30  60  40  30
WYS  35  60  32  62 /  30  60  30  20
DLN  42  63  40  68 /  50  60  20  10
HVR  54  76  52  77 /  10  20  40  20
LWT  49  71  49  69 /  20  40  70  60

&&

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

&&

http://www.weather.gov/greatfalls

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