687
FXUS65 KTFX 222035
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
135 PM MST Wed Jan 22 2025

.KEY MESSAGES...

 - Blizzard to near-blizzard conditions from the Little Belts
   eastward through Fergus county through the afternoon.

 - Another period of gusty winds Thursday over the plains, with another
   round of at least patchy blowing snow between Belt and Grass
   Range late Thursday morning through early evening.

 - A cold front brings another period of snow Thursday night through
   late Friday night, with northerly upslope areas favored for
   greatest accumulations.

 - A drier period is forecast late weekend into early next week,
   though periods of wind will still be around.

&&

.DISCUSSION...

 - Meteorological Overview:

Through the day Thursday:

Northerly to northwesterly flow aloft is in place across the
Northern Rockies as an upper level ridge remains in place across the
far eastern Pacific Ocean. Embedded waves within this flow are
combining with a modest pressure gradient across the plains to
result in blizzard conditions across portions of Central Montana.
Elsewhere winds and falling snow are lighter, resulting in less
impacts. A weakening pressure gradient through the afternoon and
early evening combined with lessening upper level support for
falling snow will allow for blizzard conditions to diminish by mid-
evening.

A more robust upper level trough currently over the Gulf of Alaska
will break down the aforementioned ridge and result in a more
zonal, but still slightly northwesterly flow aloft Thursday. An
increasing pressure gradient across the Northern Rockies will result
in a breezy day across the plains, with strong winds not out of the
questions along the Northern Rocky Mountain Front and adjacent
plains. A period of blowing snow will be possible between Belt and
Grass Range Thursday afternoon, dependent on how much blowable snow
remains after today.

Thursday evening through Saturday:

The upper level disturbance responsible for winds Thursday will
settle just south of the region going into Friday into Saturday. The
result is for a shift to a northerly flow aloft, with a cold front
dropping south from Canada introducing opportunities for snow across
the region beginning Thursday night. Snow largely looks to follow
the progression of the front southward, though looks to linger a bit
longer across Central Montana ranges.

Late Saturday into much of next week:

Model ensembles and cluster guidance are in relatively good
agreement for a rex block pattern developing next week, with a ridge
over the Pacific Northwest and cutoff low somewhere over the
southwest CONUS. This looks to keep the region near or a touch above
normal in the temperature department, with periods of gusty winds
likely. Chances for precipitation over this timeframe are low.

 - Forecast Confidence & Scenarios:

Blizzard Conditions Today:

Falling and blowing snow resulting in blizzard conditions will
remain a concern through the afternoon into the early evening from
the Little Belts eastward through Fergus county, with impacts slowly
diminishing through mid-evening. Travel will remain very difficult
to impossible in these areas through the remainder of the afternoon
due to greatly reduced visibility, gusty winds, and blowing/drifting
snow.


Wind Thursday:

Forecast soundings show a relatively strong inversion conducive to
mountain wave activity from Thursday morning through Thursday
afternoon along the Rocky Mountain Front and out to Cut Bank. At
least a three hour period of 50+kt flow within the stable layer will
yield an opportunity for stronger winds to mix to the surface in and
around Cut Bank. Additionally, an increasing pressure gradient peaks
Thursday afternoon, mostly across the Northern Rocky Mountain Front,
bringing concern for sustained strong winds as well. Hence, a High
Wind Watch has been issued for the Northern Rocky Mountain Front out
to Cut Bank for late morning Thursday through early Thursday
evening, when a cold front will move through and rapidly decrease
chances for strong winds.

Tremendous uncertainty will be in place Thursday across the 87
corridor between Belt and Grass Range for blowing and drifting snow.
Uncertainty stems from how much blowable snow will remain in the
area after today. There will be no falling snow in these areas,
which would require blowable snow to stick around into Thursday
after blizzard conditions subside today. Additional uncertainty
stems from forecast temperatures, which look to rise into the mid-
30s by the afternoon. Localized blowing snow is forecast, with
potential for more widespread blowing snow dependent on how the
remainder of today plays out. For that reason we have held off on a
Winter Weather Advisory for this area at this time.

Snow Thursday night through late Friday night:

A cold front dropping southward Thursday evening into Thursday night
will re-introduce chances for snow from north to south across the
region through the day Friday. There is roughly a 50% chance to
reach or exceed 6 inches of snow between Monarch and Neihart from
late Thursday night through the day Friday. -AM


&&

.AVIATION...
22/18Z TAF Period

The primary concern this TAF period is for a period of falling and
blowing snow, mostly across Central and North-central Montana
through the evening today. Blizzard to near-blizzard conditions are
forecast for KLWT through much of the afternoon. After the snow and
blowing snow diminishes, the next concern will be for a period of
gusty winds developing across the plains Thursday morning, with
another period of blowing snow around KLWT possible by late morning.
Mountain wave turbulence will be possible with this period of winds
beginning Thursday morning. -AM

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  10  35  21  29 /  20  10  90  40
CTB  10  32  14  26 /   0  10  60  10
HLN   7  32  18  28 /  20   0  70  60
BZN  -1  29  14  26 /  20   0  40  70
WYS -26   8   1  21 /  20   0  10  60
DLN   2  30  13  26 /  10   0   0  30
HVR   8  31  16  28 /  20  10  60   0
LWT  10  34  18  24 /  80   0  70  30

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 5 PM MST this afternoon for Big
Belt, Bridger and Castle Mountains-Eastern Toole and Liberty.

High Wind Watch from Thursday morning through Thursday afternoon
for East Glacier Park Region-Eastern Glacier, Western Toole, and
Central Pondera-Northern High Plains.

Winter Storm Warning until 9 PM MST this evening for Bears Paw
Mountains and Southern Blaine.

Blizzard Warning until 9 PM MST this evening for Fergus County
below 4500ft-Judith Basin County and Judith Gap-Little Belt and
Highwood Mountains-Snowy and Judith Mountains.

&&

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