Special Weather Statement, NWS Great Falls, MT

Area Forecast Discussion
National Weather Service Great Falls MT
114 PM MDT Mon Aug 12 2024

.SYNOPSIS...

Showers and thunderstorms will occur through at least
Friday across at least some portion of North-central, Central, and
Southwestern Montana. The showers and thunderstorms will be the most
widespread on Tuesday. Isolated thunderstorms this afternoon and
evening and Tuesday afternoon and evening will produce severe wind
gusts, large hail, and heavy rainfall. A cold front moves through
on Tuesday which cools down temperatures on Wednesday.

&&

.DISCUSSION...

This afternoon through Tuesday... This afternoon an upper-level
ridge remains over North-central, Central, and Southwestern
Montana. This afternoon through this evening an upper-level level
shortwave moves through the upper-level flow. This will cause
there to be showers and thunderstorms in the Golden Triangle
region (the region from Cut Bank to Havre to Great Falls) and
Southwestern Montana through this evening. This afternoon the
Storm Prediction Center (SPC) has issued a Marginal Risk for
severe weather(5% chance for severe wind gusts within 25 miles of
point)for the Golden Triangle region, Madison and Gallatin
Counties, and eastern Beaverhead County. Isolated thunderstorms
will produce severe wind gusts (wind gusts greater than 58 mph).
The upper-level ridge remains over North-central, Central, and
Southwestern Montana through Tuesday morning before an upper-level
trough begins moving over the area Tuesday afternoon. A cold
front associated with the upper-level trough will move through
North-central, Central, and Southwestern Montana Tuesday afternoon
through early evening. On Tuesday the SPC has issued a Marginal
Risk for severe weather(5% chance for severe wind gusts and a 5%
chance for golf ball-sized hail withing 25 miles of point) for
eastern Beaverhead, southeastern Madison, and Gallatin Counties
and Eastern Fergus and Blaine Counties. Isolated thunderstorms
will produce severe wind gusts (wind gusts greater than 58 mph)
and hail the size of golf balls (primarily in eastern Beaverhead,
southeastern Madison, and Gallatin Counties). Some thunderstorms
will produce heavy rainfall. On Tuesday locations across
Southwestern Montana have a 20 - 50% chance for receiving a
quarter inch of rain or greater. On Tuesday locations in Central
Montana have a 30 - 60% chance for receiving a tenth of an inch of
rain or greater.

Wednesday through Friday... On Wednesday the upper-level trough
remains over North-central, Central, and Southwestern Montana. This
will allow for showers and thunderstorms in the afternoon and
evening across the area. Due to the cold front that moves through on
Tuesday temperatures will be 5 to 10 degrees below seasonal averages
across the lower-elevation's of North-central, Central, and
Southwestern Montana on Wednesday. On Wednesday locations across
Southwestern Montana have a 40 - 60% chance for receiving a tenth of
an inch of rain or greater. On Thursday an upper-level ridge moves
back over North-central, Central, and Southwestern Montana. However,
an upper-level shortwave moves through the upper-level flow and
will bring showers and thunderstorms to the area. On Thursday all
lower-elevations of North-central, Central, and Southwestern
Montana have a 20 - 40% chance for a tenth of an inch of rain or
greater. On Friday the upper-level ridge remains over North-
central, Central, and Southwestern Montana. However, an upper-
level shortwave moves through the upper-level flow and will bring
showers and thunderstorms to the area.

Saturday through next Monday... On Saturday clusters show an upper-
level ridge over North-central and Central Montana with an upper-
level trough beginning to move over the area. This will keep similar
weather on Saturday to Friday. On Sunday and Monday deterministic
models and clusters begin to diverge. This will continue to be
monitored for details. -IG

&&

.AVIATION...
12/18Z TAF Period

The primary concern this TAF period will be for showers and widely
scattered thunderstorms this afternoon and evening. Gusty winds are
the main concern with thunderstorms, with small hail being a lesser
concern. Wildfire smoke may obscure distant mountains and reduce
slant-range visibility. Additional showers will be around late
morning tomorrow, but mention in TAFs was excluded for now due to
low confidence in terminal impacts. -AM

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  55  83  56  78 /  10  40  40  30
CTB  52  82  54  78 /  20  20  20  20
HLN  56  83  55  80 /  20  60  50  40
BZN  52  80  49  78 /  20  60  60  50
WYS  44  70  39  68 /  40  70  60  70
DLN  50  76  46  73 /  10  70  40  40
HVR  56  89  59  83 /  20  20  30  20
LWT  52  83  52  76 /  10  30  60  40

&&

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

http://www.weather.gov/greatfalls

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