574
FXUS65 KTFX 121513
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
813 AM MST Wed Feb 12 2025

.KEY MESSAGES...

 - Winds increase this afternoon through tomorrow which will lead
   to blowing snow across portions of North-central, Central, and
   Southwestern Montana.

 - Friday through Saturday morning there will be widespread snow
   across North-central, Central, and Southwestern Montana.

 - After a brief warm up on Thursday, cold air returns to North-
   central and Central Montana on Friday and Saturday before
   temperatures warm up on Sunday through early next week.

&&

.UPDATE...

Patchy dense fog has developed across portions of Central and
North-central Montana this morning under clear skies. These clear
skies have also contributed to a cold start, with temperatures
across the region mostly below -10F.

As winds slowly develop through the day today, patchy
blowing/drifting drifting snow concerns will develop along the
Rocky Mountain Front. These concerns spread into the Madison River
Valley and other north south oriented valleys of Southwest
Montana heading into tomorrow.

No significant changes were necessary at this time, with small
tweaks made to account for current trends. The Cold Air
Advisories and Extreme Cold Warning in effect through 11 AM today
remain unchanged at this time, with additional warnings and
advisories going into effect this evening for the overnight. -AM

&&

.DISCUSSION...
/Issued 448 AM MST Wed Feb 12 2025/

 - Meteorological Overview:

A quick moving shortwave is bringing light snow to a portion of
North-central and Central Montana this morning. Due to clear skies
in Southwestern Montana patchy fog has the potential to form. Today
an upper-level ridge begins to move over North-central, Central, and
Southwestern Montana. This upper-level ridge remains over North-
central, Central, and Southwestern Montana on Thursday. This will
gradually warm up temperatures today and Thursday. Due to a strong
surface pressure gradient this afternoon winds will increase across
much of North-central and Central Montana this afternoon through
tonight with the strongest winds along the Rocky Mountain Front.
Along the Rocky Mountain Front and the Montana Highway 200/US
Highway 87 Corridor between Great Falls and Lewistown there will be
blowing snow this afternoon and evening with the greatest impacts
along the Rocky Mountain Front. On Thursday there will be a strong
surface pressure gradient in Southwestern Montana. This will lead to
gusty winds in Southwestern Montana with the strongest winds in
north-south oriented valleys. As a result there will be blowing snow
in Southwestern Montana on Thursday.

Friday morning an upper-level trough combined with an arctic front
will bring another blast of cold air from Canada to North-central
and Central Montana on Friday and Saturday which will cool
temperatures back down. Friday through Saturday morning due to the
warm air in Southwestern Montana and warm air aloft combined with
Pacific moisture there will be an overrunning snow event in North-
central and Central Montana and snow in Southwestern Montana. On
Saturday an upper-level ridge begins to build back in over North-
central, Central, and Southwestern Montana. The upper-level ridge
remains over the area through Tuesday. Due to northwest flow aloft
combined with pacific moisture from upper-level shortwaves there
will be periods of snow across much of North-central, Central, and
Southwestern Montana from Sunday morning through Tuesday morning.
Due to the upper-level ridge temperatures Sunday through Tuesday
will be warmer than this week across the area.

 - Forecast Confidence & Scenarios:

For blowing snow today there is high confidence that it will occur
this afternoon through tonight along the Rocky Mountain Front.
However there is low confidence that it will lead to minor winter
weather impacts and so a Winter Weather Advisory was not issued at
this time. There is a moderate confidence that blowing snow will
occur along the Montana Highway 200/US Highway 87 Corridor between
Great Falls and Lewistown this afternoon through tonight. As a
result a Winter Weather Advisory was not issued at this time. On
Thursday there is high confidence in blowing snow occurring in
Southwestern Montana with the greatest impacts in north-south
oriented valleys.

For fog this morning there is a 30 - 60% chance for it to form in
the Helena and Gallatin Valley. For snow Friday through Saturday
across most of the lower-elevations of North-central, Central, and
Southwestern Montana there is a 30 - 50% chance for an inch of
snow or greater. Along the Montana Highway 200/US Highway 87
Corridor there is a 60 - 80% chance for 2 inches of snow or
greater Friday through Saturday. Across the mountains of North-
central, Central, and Southwestern Montana there is a 30 - 50%
chance for four inches of snow or greater from Friday through
Saturday. For snow Sunday through Tuesday across most of the
lower-elevations of North-central and Central Montana there is a
40 - 80% chance for two inches of snow or greater. For snow Sunday
through Tuesday across most mountain locations of North-central,
Central, and Southwestern Montana there is a 50 - 80% chance for 8
inches of snow or greater.

Today there is a 70 - 90% chance for highs below zero in the
Gallatin Valley over to the Canyon Ferry area and in Northern Hill
and Blaine Counties. For cold high temperatures on Friday and
Saturday there is a 30 - 70% chance for highs below 0 across the
plains of North-central Montana. This morning there is around a 50 -
80% chance for lows of 20 below or colder along the Hi-Line, in the
Helena Valley, and valleys of Southwestern Montana. On Thursday
morning there is greater than a 80% chance for lows of 20 below or
colder in the Gallatin Valley and cold prone valleys of Southwestern
Montana. Thursday morning there is a 70 - 90% chance for low
temperatures of 10 below or colder across Southwestern Montana. As a
result of this, plus the stronger winds for much of North-central,
Central, and Southwestern Montana an Extreme Cold Warning was
issued for Southwestern Montana and a Cold Weather Advisory was
issued for North-central and Central Montana for tonight through
Thursday morning. Saturday morning along the Hi-Line there is a 60
- 90% chance for low temperatures of 10 below or colder. -IG

&&

.AVIATION...
12/12Z TAF Period

Mostly VFR conditions are expected for this TAF period; however,
transient areas of low stratus and patchy fog will persist in the
vicinity of the terminals through 12/16Z or so. Intermittent MVFR
and even IFR/LIFR conditions can be expected at times, with the
worst conditions currently at KEKS and KLWT. Otherwise, west to
southwesterly surface winds increase along the Rocky Mountain
Front and adjacent plains this afternoon and tonight, with gusts
generally in the 20 to 30 kt range. - RCG

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  12  -2  17   3 /  20   0   0  50
CTB  12  -7  11  -5 /   0   0   0  20
HLN   4 -10  17   2 /   0   0   0  40
BZN   1 -26  21   8 /   0   0   0  30
WYS   9 -33  23  11 /   0   0  10  70
DLN   5 -17  17   9 /   0   0   0  10
HVR   3 -10  12  -4 /   0   0   0  10
LWT   8  -4  24   1 /  10   0   0  40

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Cold Weather Advisory until 11 AM MST this morning for Bears Paw
Mountains and Southern Blaine-Beaverhead and Western Madison
below 6000ft-Big Belt, Bridger and Castle Mountains-Canyon Ferry
Area-Cascade County below 5000ft-East Glacier Park Region-
Eastern Pondera and Eastern Teton-Elkhorn and Boulder Mountains-
Fergus County below 4500ft-Gallatin Valley-Gallatin and Madison
County Mountains and Centennial Mountains-Gates of the Mountains-
Helena Valley-Judith Basin County and Judith Gap-Little Belt and
Highwood Mountains-Madison River Valley-Meagher County Valleys-
Missouri Headwaters-Northern High Plains-Northwest Beaverhead
County-Ruby Mountains and Southern Beaverhead Mountains-Snowy
and Judith Mountains-Southern High Plains-Southern Rocky
Mountain Front-Upper Blackfoot and MacDonald Pass-Western and
Central Chouteau County.

Cold Weather Advisory from 6 PM this evening to 11 AM MST
Thursday for Bears Paw Mountains and Southern Blaine-Big Belt,
Bridger and Castle Mountains-Cascade County below 5000ft-East
Glacier Park Region-Eastern Glacier, Western Toole, and Central
Pondera-Eastern Pondera and Eastern Teton-Eastern Toole and
Liberty-Elkhorn and Boulder Mountains-Fergus County below 4500ft-
Gates of the Mountains-Helena Valley-Hill County-Judith Basin
County and Judith Gap-Little Belt and Highwood Mountains-
Northern Blaine County-Northern High Plains-Snowy and Judith
Mountains-Southern High Plains-Southern Rocky Mountain Front-
Upper Blackfoot and MacDonald Pass-Western and Central Chouteau
County.

Extreme Cold Warning until 11 AM MST this morning for Eastern
Glacier, Western Toole, and Central Pondera-Eastern Toole and
Liberty-Hill County-Northern Blaine County.

Extreme Cold Warning from 6 PM this evening to 11 AM MST
Thursday for Beaverhead and Western Madison below 6000ft-Canyon
Ferry Area-Gallatin Valley-Gallatin and Madison County Mountains
and Centennial Mountains-Madison River Valley-Meagher County
Valleys-Missouri Headwaters-Northwest Beaverhead County-Ruby
Mountains and Southern Beaverhead Mountains.

&&

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