934
FXUS65 KTFX 191611
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
911 AM MST Sun Jan 19 2025

.KEY MESSAGES...

 - Very cold temperatures persist through Tuesday morning, with
   Monday being the coldest.
 - Very light snow develops today across the Divide, Central, and
   Southwest MT.
 - Windy conditions expected along the Rocky Mountain Front
   Monday night and Tuesday.
 - Next round of widespread snow will be Friday into Saturday.

&&

.UPDATE...

Northwesterly flow aloft continues across the region as an amplified
ridge nudges eastward across the far eastern Pacific Ocean. Within
this northwesterly flow aloft there exists just enough moisture to
wring out light snow across the Northern Rockies. Expectation is for
snow to remain quite light in nature today, with additional
accumulations totaling up to a half of an inch or so. Another push
of northerly winds arrives late this morning into the afternoon
as surface high pressure nudges southwestward in Alberta, which
may result in a brief period of blowing and drifting snow over the
plains. Confidence in this lasting much longer than a half of an
hour or so is low though, given the low amount of blowable
snowpack.

Northerly to northwesterly surface winds persist across much of the
plains into the evening and into early Monday, which will allow for
wind chill temperatures to drop below -25F in most areas. A
pressure gradient will develop late tonight crossing the
Continental Divide, initiating southwest winds along the
immediate eastern slopes of the Rockies. This will result in
light southwesterly winds in these areas, keeping the window for
the coldest wind chills to a few hours before temperatures begin
to rise. Wind chills below -35 will be possible across areas in
Hill and Blaine counties. We are considering an upgrade to an
Extreme Cold Warning for this area and will make a final decision
early this afternoon. -AM

&&

.DISCUSSION...
/Issued 513 AM MST Sun Jan 19 2025/

 - Meteorological Overview:

Temperatures have dropped to the single digits to negative teens(a
few below low 20s) across the region this morning. Temperatures
won`t warm up too much today, only reaching near 0 to single
digits across the North-Central MT plains and to the teens across
the Southwest Valleys. Embedded disturbances within this northwest
flow aloft pattern will bring very light snow across the Divide,
Central, and Southwest MT today, but little snow accumulations are
expected. This arctic airmass will bring in colder air for Monday
morning, with wind chill values dropping as low as 35 below
across the plains and the southwest valleys towards the Idaho
border.

This upper level ridge breakdowns late Monday night and Tuesday.
brining in gusty winds across the Rocky Mountain Front and the
North Central MT plains. This will begin the warm up back to
close to normal temperatures Tuesday. There`s a slight chance for
light snow east of the Inverness to Bozeman line late Tuesday
night and early Wednesday morning as well from this ridge
breakdown. Breezy winds continue across Fergus and Blaine Counties
Wednesday. The next winter system arrives along a cold front
Friday and Saturday.


 - Forecast Confidence & Scenarios:

Snow:

Hi-resolution model guidance are in good agreement for the typical
"dirty northwest flow pattern" light snow today. Little
accumulations of up to 1-2" are expected at higher elevations.

There is a big spread in snowfall amounts Friday and Saturday. The
current patterns highlights the favored northerly upslope snow
areas across the Montana Highway 200 corridor/Little Belts region.
There`s about a 30% chance for 8" of snow. The 25th-75th
percentile (lower end to higher end amounts) range between 4-12"
of snow, showing the uncertainty in snowfall amounts.

Cold Temperatures:

The Browning and Boulder Hill areas were added to the Cold
Advisory Monday morning, since there was a 60-80% for reaching
-25 degree wind chills. Along the Hi-Line, there`s good
 confidence for wind chills dropping to -30 to -35 degrees.
 Isolated -40 below is possible, but with not as much confidence
 in these temperatures being widespread, I turned the Extreme Cold
 Watch into to a Cold Advisory. How quickly we warm up Tuesday
 morning will depend on how quick the warm downsloping winds
 arrive across the plains.

Winds:

The NBM(National Blend of Models) puts the Cut Bank area in a
50-70% chance for 55mph winds Tuesday. Looking at the overall
synoptic set up and forecast soundings in the area, I am not
overly confident for strong winds at this time. Though we will
monitor this in future forecast packages. -Wilson

&&

.AVIATION...
19/12Z TAF Period

Expect VFR to MVFR conditions to persist across the area as an
arctic air mass settles into the area. Will likely have a few
scattered snow showers, especially around KHLN, KEKS, and KBZN
today as a second surge of cold air pushes into the area. Ludwig

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF   4 -17  14   6 /  30  10   0   0
CTB   4 -19  15   7 /  30  10   0   0
HLN  13 -13   7   2 /  30  20   0   0
BZN  13 -23   5  -8 /  30  20   0   0
WYS  14 -35   5 -23 /  40  20   0   0
DLN  18 -14   5  -3 /  30  30   0   0
HVR  -2 -21   3  -4 /  20   0   0   0
LWT   0 -17   9  -3 /  30  10   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Cold Weather Advisory from 5 PM this afternoon to noon MST
Monday for Bears Paw Mountains and Southern Blaine-Big Belt,
Bridger and Castle Mountains-Cascade County below 5000ft-Eastern
Glacier, Western Toole, and Central Pondera-Eastern Pondera and
Eastern Teton-Eastern Toole and Liberty-Elkhorn and Boulder
Mountains-Fergus County below 4500ft-Hill County-Judith Basin
County and Judith Gap-Little Belt and Highwood Mountains-Meagher
County Valleys-Northern Blaine County-Northern High Plains-Snowy
and Judith Mountains-Western and Central Chouteau County.

Cold Weather Advisory from midnight tonight to 9 AM MST Monday
for Gallatin and Madison County Mountains and Centennial
Mountains-Ruby Mountains and Southern Beaverhead Mountains.

&&

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