287
FXUS65 KTFX 121515
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
915 AM MDT Wed Mar 12 2025

.KEY MESSAGES...

 - It will be windy in Southwestern Montana on Wednesday and
   Thursday with the strongest winds in north-south oriented
   valleys on Wednesday.

 - Thursday through this weekend there will be mountain snow with
   primarily rain at some of the lower elevations of North-central
   and Central Montana on Thursday and Friday and a rain/snow mix
   at the lower-elevations of Southwestern Montana on Thursday and
   Friday.

 - Winds will increase on Sunday before the next system will move
   through early next week.

&&

.UPDATE...

No major changes with the update this morning. Ludwig

&&

.DISCUSSION...
/Issued 506 AM MDT Wed Mar 12 2025/

 - Meteorological Overview:

Today an upper-level ridge builds in over North-central, Central,
and Southwestern Montana. This will warm temperatures up slightly.
Wednesday afternoon and evening an upper-level shortwave will move
through bringing light snow to the higher-elevations of North-
central, Central, and Southwestern Montana. This afternoon and
evening due to strong upper-level flow it will be windy across
Southwestern Montana with the strongest winds in north-south
oriented valleys.

On Thursday an upper-level trough associated with a surface cold
front will move through North-central, Central, and Southwestern
Montana. This will bring precipitation to most of the area with the
greatest amounts south of the Montana Highway 200/US Highway 87
Corridor. At lower-elevation locations the precipitation will start
out as rain or a rain/snow mix for some lower-elevation locations in
Southwestern Montana. Due to warm temperatures and some instability
combined with the frontal passage there is the potential for a
rumble of thunder in Southwestern Montana Thursday afternoon and
evening. This could produce a brief heavy downpour and/or an intense
snow shower/snow squall. See the Forecast Confidence & Scenarios
section for more details. Late Thursday evening rain will transition
to snow at lower-elevations of Southwestern Montana. The rain/snow
transition will gradually move north to the Montana Highway 200/US
Highway 87 Corridor by early Friday morning. On Thursday due to
strong upper-level winds and a strong surface pressure gradient it
will be windy across Southwestern Montana and along the Rocky
Mountain Front and adjacent plains. The upper-level trough will
remain over North-central, Central, and Southwestern Montana on
Friday which will bring cooler temperatures to the area on Friday.
Snow will gradually end Friday morning with the highest snow
amounts in the Madison and Gallatin Mountains.

On Saturday weak upper-level ridging builds in over North-central,
Central, and Southwestern Montana. An embedded upper-level shortwave
will move through the upper-level ridge which will bring light snow
primarily to the mountains of North-central, Central, and
Southwestern Montana on Saturday. The upper-level ridge amplifies on
Sunday which will bring warmer temperatures and windy conditions to
North-central, Central, and Southwestern Montana. Additionally an
upper-level shortwave will bring snow to the mountains on Sunday.
Monday through Tuesday an upper-level trough will move over the area
this will cool down temperature bring precipitation to at least a
portion of North-central, Central, and Southwestern Montana. -IG

 - Forecast Confidence & Scenarios:

For winds on Wednesday there is a 30 - 80% chance for sustained
winds of 40 mph or greater along the Madison River Valley. For winds
on Wednesday there is a 30 - 60% chance for wind gusts of 55 mph or
greater across most of Southwestern Montana. Due to the strong
sustained winds occurring for only a few hours a High Wind Warning
was not issued. For winds on Thursday there is a 30 - 60% chance for
wind gusts of 55 mph or greater across most of Southwestern Montana.
On Thursday there is a 20 - 80% chance for sustained winds of 40 mph
or greater along the Madison River Valley. For winds on Thursday
there is a 50 - 80% chance for wind gusts of 55 mph or greater along
the Rocky Mountain Front and Adjacent Plains. Due to low confidence
in severe winds occurring for 6 hours or longer no High Wind
Products were issued for Thursday. For winds on Sunday there is a 50
- 90% chance for wind gusts of 55 mph or greater across most of
Southwestern Montana and along the Rocky Mountain Front and adjacent
plains.

For snow squalls on Thursday: There is a 15% chance for thunder
Thursday afternoon and early evening. There is a around a 50% chance
for greater than 50 J/kg of instability (CAPE). This is enough to be
supportive of snow squalls. Due to warm afternoon temperatures when
the frontal passage is forecast to occur, at this time across most
lower-elevation locations of Southwestern Montana a brief a heavy
downpour is favored over a snow squall. In the West Yellowstone area
due to the frontal passage occurring later combined with colder
temperatures a snow squall would be more likely to occur. However
there will be less instability at the time of frontal passage which
will reduce the threat for a snow squall. Additionally the precise
timing of frontal passage is uncertain at this time. So the
overall risk for a snow squall in Southwestern Montana Thursday
afternoon and early evening is low at this time. Due to the low
probability for thunder there is a low risk for a brief heavy
downpour across the lower-elevations of Southwestern Montana.

For snow Thursday through Friday there is a 50 - 80% chance for 8
inches of snow or greater across the higher elevations of the
Madison and Gallatin Mountains. For snow Thursday through Friday
there is a 30 - 60% chance for 4 inches of snow or greater in
Northwestern Beaverhead County and at pass-level in the Madison
and Gallatin Mountains. As a result Winter Weather Advisories were
issued for those locations. Monida Pass has around a 50% chance
for 4 inches of snow or greater but due to probabilities falling
off rapidly north of Monida Pass a Winter Weather Advisory for
that area was not issued at this time. For snow Saturday through
Sunday there is a 20 - 50% chance for 2 inches of snow or greater
across the mountains of Southwestern Montana and a 60 - 80% chance
for 4 inches of snow or greater along the Rocky Mountain Front. -IG

&&

.AVIATION...
12/12Z TAF Period

VFR conditions will prevail during all of this TAF Period at all
terminals. It will be windy at the KEKS terminal during the duration
of this TAF Period with winds peaking around the middle of this TAF
Period. There will be isolated instances of mountain wave turbulence
and low-level wind shear across Southwestern Montana from 13/00Z on
through the end of the TAF Period. -IG

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  61  37  59  28 /  10  10  30  20
CTB  55  29  54  19 /  10   0  10   0
HLN  59  36  54  26 /  10  10  60  40
BZN  55  31  53  21 /   0  10  60  70
WYS  44  28  41  16 /  10  60  90  90
DLN  57  33  50  21 /   0  20  80  60
HVR  58  32  62  23 /  10   0  10  20
LWT  55  35  57  26 /  10  10  40  60

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 6 AM Thursday to 6 AM MDT Friday
for Gallatin and Madison County Mountains and Centennial
Mountains.

Winter Weather Advisory from midnight tonight to midnight MDT
Thursday night for Northwest Beaverhead County.

&&

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