435
FXUS65 KTFX 081719
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1019 AM MST Wed Jan 8 2025

.KEY MESSAGES...

-  Windy conditions and varying degrees of blowing and drifting
   snow continue along the Rocky Mountain Front and portions of
   the plains through this afternoon.

-  Another quick round of snow moves through the northern plains
   today and tonight

-  Winds increase along the Rocky Mountain Front and the plains
   again on Friday before periods of accumulating snow and cooling
   temperatures move in for the weekend.

&&

.UPDATE...
1015 AM...Strong winds continue to affect the Cut Bank area. Thus
a high wind warning was issued until late afternoon in this area.
Otherwise, the main band of snow moving southeastward through the
CWA is now moving into Central MT. The winter weather advisory for
this area was pushed up in time to start now. Otherwise, snowfall
forecast are on track from previous forecasts. The snow lets up
tonight, but another round of snow is expected Friday night into
Saturday, and additional winter statements might be needed for
that event. Brusda

540 AM...Dense fog along highway 287/12 from Helena to Bozeman
has largely dissipated, so the dense fog advisory was canned
early. - RCG

&&

.DISCUSSION...
/Issued 545 AM MST Wed Jan 8 2025/

 - Meteorological Overview:

An active northwesterly flow aloft will send a series of troughs,
interrupted by transient ridges, through the region for the next
week or so. Overnight ridging aloft combined with inversions have
maintained stubborn dense fog along the highway 12/287 corridor
between Helena and Bozeman. Higher clouds and cooler air aloft
moving in will work to dissipate this fog early this morning.
Otherwise, the focus continues to be the tightening surface
pressure gradient and resultant strong gusty winds along the Rocky
Mountain Front and plains. Overnight wind speeds have generally
stayed within the 25 to 45 mph range for sustained winds and 40 to
70 mph for gusts, with Cut Bank seeing the highest representative
winds so far. Winter weather impacts from blowing and drifting
snow will continue until temperatures sufficiently rise above
freezing and snow scours out later today. Snow drifting and
potential road blockages loom to be the primary concern going
forward rather than visibility reductions.

A fast moving shortwave then dives southeastward this afternoon
and tonight for a quick round of light to moderate snow over and
near the Central Montana island ranges and the Madison/Gallatin
mountains. While winds diminish this afternoon along the Rocky
Mountain Front and the western plains, winds shift to the
northwest and remain gusty for locations east of Great Falls to
Havre line. This may be accompanied by quick bursts of snow for
short term lower elevation impacts this evening.

After a brief cool down and dry conditions on Thursday, transient
ridging returns on Friday with another windy day and milder
temperatures along the Rocky Mountain Front/plains before a series
of shortwaves bring periods of snow and cooling temperatures this
weekend. Mountain areas will be favored for the heavier snow, but
most lower elevations will see at least some accumulations. There
will be another round of transient ridging for drier conditions
and slightly milder temperatures. - RCG

 - Forecast Confidence & Scenarios:

Fog in Helena/Bozeman highway 12 corridor.

Mid- and higher level clouds have indeed thinned out the dense
fog, but left the dense fog advisory out for now with
probabilities for less than 1 mile visibility still running around
40 to 50% through mid-morning. This will be reevaluated as the
morning progresses for a potential early cancellation.

Winds and blowing/drifting snow.

Winds and associated winter weather impacts will peak this
morning along the Rocky Mountain Front and the western plains. The
gusty winds may persist a little longer for locations farther
east, especially for areas east of a Havre to Great Falls line
where winds will shift northwesterly in the afternoon and remain
gusty through the evening hours. No changes were made the ongoing
winter weather advisories nor their expected impacts. Roughly
similar winds are expected again on Friday, though the winter
impacts will be far less due to the melting/scouring out of the
snow pack.

Snow today and tonight.

Snowfall amounts look to remain light outside of the central
island ranges and the Madison/Gallatin mountains where NBM
probabilities for 2" or more are running over 80%. The Little Belt
Mountains look to see the highest accumulations, generally in the
4 to 10 inch range. Lower elevations may see some snow, though
accumulations look to be negligible; however, there is an
expectation for at least some short term minor impacts this
afternoon and evening for locations east of Great Falls to Havre
line due to snow shower activity and gusty northwesterly winds. No
changes were made to the ongoing winter weather advisories
covering this snow.

This weekend`s snow.

By Friday afternoon/evening the first of a series of more potent
disturbances within northwest flow will begin to approach the
Northern Rockies and bring more impactful snow to mountain areas,
mainly the central island ranges and the Madison/Gallatin
mountains. NBM probabilities for 4 inches or more of snow range
from 70-90% for both of these areas Friday afternoon through
Saturday evening, with 30 to 50% chance for 12 inches snow or more
over the Little Belts. Lower elevations don`t look to do as well
as the mountains, but the parade of disturbances with colder air
aloft will likely send at least periods of minor accumulations
through out the weekend. - RCG


&&

.AVIATION...
08/18Z TAF Period

Main concern is strong winds/blowing snow in the Cut Bank area
today, along with light snow over Central and Southwest MT. The
strong winds in the Cut Bank area will diminish late this
afternoon. However, do expect blowing snow with reduced
visibility until mid afternoon in this area. The light snow will
affect areas around Helena, Bozeman and Lewistown through this
afternoon, with the snow diminishing overnight. Do expect IFR or
lower conditions in areas of snow. Mountains passes will also be
obscured in areas of falling snow over Central and Southwest MT.
Brusda

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  39  18  33  19 /  60  40   0   0
CTB  37  14  30  19 /  30  20   0   0
HLN  40  22  35  19 /  40  70   0   0
BZN  35  19  33  12 /  50  70   0   0
WYS  22   3  27   1 /  50  70   0   0
DLN  35  16  31  14 /  10  30   0   0
HVR  41  17  30  12 /  60  30   0   0
LWT  37  19  33  15 /  80  80   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Warning until 4 PM MST this afternoon for Eastern
Glacier, Western Toole, and Central Pondera.

Winter Weather Advisory until 5 PM MST this afternoon for
Cascade County below 5000ft-East Glacier Park Region-Eastern
Glacier, Western Toole, and Central Pondera-Eastern Toole and
Liberty-Fergus County below 4500ft-Hill County-Judith Basin
County and Judith Gap-Northern Blaine County-Northern High
Plains-Southern High Plains-Southern Rocky Mountain Front.

Winter Weather Advisory until 11 PM MST this evening for Bears
Paw Mountains and Southern Blaine.

Winter Weather Advisory until 5 AM MST Thursday for Big Belt,
Bridger and Castle Mountains-Gallatin and Madison County
Mountains and Centennial Mountains-Little Belt and Highwood
Mountains-Snowy and Judith Mountains.

&&

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