834
FXUS65 KTFX 311036
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
336 AM MST Fri Jan 31 2025

.KEY MESSAGES...

 - Strong winds develop today in the Madison River Valley and tonight
   along the Rocky Mountain Front with locally strong winds
   expected across portions of central and north-central Montana
   on Saturday.

 - Impactful winter weather develops later today and tonight across
   northern portions of the continental divide and becomes more
   widespread across the area this weekend into early next week.

 - An Arctic airmass moves south into the region Saturday night
   and Sunday and lingers through early next week with the
   greatest risk for subzero temperatures and periods of hazardous
   wind chill across north-central Montana

&&

.DISCUSSION...

 - Meteorological Overview:

An upper level low digs south from the AK panhandle to a position
near Vancouver island this weekend, setting the stage for a
period of increasingly impactful winter weather across the area
going into early next week.

Mid-level west to southwest flow increases today as an initial
Pacific cold front and plume of moisture moves onshore and into the
Northern Rockies by this evening. An already strong pressure gradient
across southwest MT and better alignment with SW mid-level flow will
support stronger winds today through the Madison River Valley while
orographic snow develops later this afternoon and evening along
portions of the continental divide both near the WY/ID border and
along the Rocky Mtn Front and Glacier Park region. A second
Pacific frontal system with colder air aloft passes through the
region on Saturday with surface low pressure emerging in southern
AB and shifting east into southern SK by Saturday evening. A
period of heavier snow develops ahead of this feature tonight
through Saturday morning along the higher elevations of the Rocky
Mountain Front while stronger westerly mid-level flow and the
passage of the Pacific cold front support strong winds along areas
east of the Rocky Mountain Front and locally across portions of
north-central MT on Saturday, including portions of Cascade and
Judith Basin counties.

High pressure and an Arctic airmass building in NW Canada surges
south behind the surface low moving into SK late Saturday and across
across the north-central MT plains Saturday night before slowly
filtering into SW MT by early next week. The primary impact from the
passage of the Arctic front will be a period of gusty north winds
and rapidly falling temperatures across the plains as deeper Pacific
moisture will be south of the region by then with primarily light
snow or flurries following the frontal passage.

The cold airmass will deepen across the plains through early next
week with daytime temperatures in the single digits above/below zero
through at least Wednesday. Meanwhile the upper level low lingering
in the Pacific NW vicinity will redirect mid and upper level Pacific
moisture back to the north with snow becoming more widespread from
south to north Monday through Wednesday.

 - Forecast Confidence & Scenarios:

Wind: Probabilities for strong winds (sustained > 34kts or gusts >
48kts) remain in the 60-80% range with enough potential to upgrade
previously issued High Wind Watches to Warnings.

Saturday Pacific Front: Sufficient cooling aloft will occur Saturday
afternoon to create marginal instability and the potential for
convective snow showers/bands, mainly across areas from Helena
south through SW MT. The frontal passage and any convective
precipitation could produce brief but intense snow and visibility
reductions and stronger wind gusts with afternoon timing favoring
areas along the I-90 corridor.

Arctic Front and extent of much colder air this weekend: There
remains some uncertainty in the specific timing of the much colder
air Saturday night and especially with its timing into southwest MT.

Bitter Cold: Forecast guidance continues to trend colder across
north-central MT for the late Sunday through Wednesday period with
probabilities for subzero daytime max temperatures Monday and
Tuesday ranging from 80% or higher across all of north-central  MT to
around 60% as far south as Helena. Wind chill/cold weather hazards
are likely for portions of north-central MT during this period.

Valley/Plains snow potential: Tuesday-Wednesday period looks to hold
the best potential for impactful snow accumulation at lower
elevations but there is still a fair amount of uncertainty in the
amounts. Currently there is a 30-50% chance of 2-day snow totals
exceeding 4 inches across lower elevations including Great Falls
Helena, Havre, Lewistown and Bozeman but reasonable low end amounts
(25th percentile) are around 1 inch with reasonable high end amounts
(75th percentile) around 6 inches. Hoenisch

&&

.AVIATION...
31/06Z TAF Period

KEKS: Winds will steadily increase at KEKS through the next 24
hours, with 50 kt winds likely by the end of the TAF period. Aside
from the winds, expect VFR conditions with just a 30% chance of a
snow shower causing MVFR conditions after 21z.

Elsewhere: VFR conditions will be the norm across North Central
and Southwestern Montana over the next 24 hours. Winds will be
gusty, especially at KGTF and KCTB during the daytime on Friday,
but otherwise expect no significant weather to impact flight
operations. Ludwig

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  48  35  44   4 /   0   0  10  10
CTB  44  27  39  -8 /   0  10  10  20
HLN  41  27  39  12 /   0  20  60  20
BZN  38  22  39  12 /   0  20  60  40
WYS  27  17  30  16 /  50  90  80  50
DLN  35  21  40  16 /  10  10  40  10
HVR  40  27  42  -5 /  10  10  10   0
LWT  43  30  42   7 /   0  10  20  30

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning from 8 AM this morning to 5 AM MST Sunday
for East Glacier Park Region-Southern Rocky Mountain Front.

High Wind Warning from 11 PM this evening to 8 PM MST Saturday
for Cascade County below 5000ft-Eastern Glacier, Western Toole,
and Central Pondera-Judith Basin County and Judith Gap-Northern
High Plains.

Winter Storm Watch from late Saturday night through Monday
afternoon for Big Belt, Bridger and Castle Mountains-East
Glacier Park Region-Elkhorn and Boulder Mountains-Gallatin and
Madison County Mountains and Centennial Mountains-Little Belt
and Highwood Mountains-Northwest Beaverhead County-Snowy and
Judith Mountains-Southern Rocky Mountain Front-Upper Blackfoot
and MacDonald Pass.

Winter Weather Advisory from 5 PM this afternoon to 5 AM MST
Sunday for Gallatin and Madison County Mountains and Centennial
Mountains.

High Wind Warning from noon today to 6 PM MST Saturday for
Madison River Valley.

Winter Storm Warning from 8 PM this evening to 5 AM MST Sunday
for Northwest Beaverhead County.

&&

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