754
FXUS65 KTFX 230026
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
526 PM MST Sat Feb 22 2025

Aviation Section Updated.

.KEY MESSAGES...

 - Periods of strong winds through the upcoming week.

 - Low confidence for patchy light freezing rain at times heading
   into early this week in cold prone areas.

 - Continued mild conditions in most areas.

 - Moderate to heavy snow largely above pass level along the Continental
   Divide through the next few days.

 - Mild temperatures will lead to snowmelt and breaking up of ice on
   rivers, both of which may result in localized flooding.

&&

.DISCUSSION...
/Issued 142 PM MST Sat Feb 22 2025/

 - Meteorological Overview:

The first half of the week will be dominated by zonal flow with
embedded waves progressing through the flow across the Northern
Rockies. Windy conditions will be around through much of the week,
and will be amplified with the passage of each of these embedded
waves aloft. The first arrives tonight, allowing for a period of
strong winds across the central and western plains, with the
strongest winds favored along the immediate eastern slopes of the
Rocky Mountain Front, where gusts in excess of 90 mph have a
greater than 50% of occurring (Mainly in wind prone areas). Patchy
blowing snow will be possible here again tonight, but there is
tremendous uncertainty given another full day of above freezing
temperatures and lack of confidence in available snowpack.
Further south, a strong pressure gradient will allow for patchy
blowing snow and strong winds at times in the Madison River Valley
from this evening into Monday.

Another wave passes across the region Sunday night into Monday,
which looks to bring a more widespread high wind threat across the
plains, perhaps into more of Central Montana as well.

Meanwhile, Pacific moisture flowing through the zonal flow aloft
will result in periods of precipitation through the next few days.
Moderate to heavy snow is forecast above pass level along the
Continental Divide (Mostly along the Northern Rocky Mountain
Front), with light snow at lower elevations along the divide.
Although low probability, precipitation that makes it across the
Continental Divide into Southwest Montana valleys looks to fall as
rain. In areas that have not warmed much and still have cold
surfaces, this rain may end up falling as freezing rain. Trends
will need to be monitored for this threat over the next couple
days.

An additional wave passes across the region late Monday night into
the day Tuesday, which looks to be another favorable period for
strong winds. Cool air aloft under the core of this system has at
least a low-end chance of resulting in weak instability across
Southwest Montana, which could result in a few showers or snow
showers.

Upper level ridging looks to take hold after Tuesday night, though
periods of gusty winds do look to remain, which will keep
temperatures on the mild side through the week. -AM

 - Forecast Confidence & Scenarios:

Winds Tonight into Sunday:

Confidence is very high for strong winds along the immediate eastern
slopes of the Rocky Mountain Front tonight into Sunday, with high
confidence for strong winds further east onto the plains. A
potentially high impact but low confidence scenario for tonight
along the Rocky Mountain Front is for the strong winds to break the
crust of the remaining snowpack, which would result in another
period of impactful blowing snow. Confidence in this is low given
another day of above freezing temperatures in addition to low
confidence in how much snow depth is left where winds will be
strongest. Trends will be monitored for any changes in confidence in
impacts.

Winds Sunday night into Monday:

Confidence for a more widespread strong wind threat exists for this
timeframe, with strong winds stretching across all of the plains and
into portions of Central Montana. Additional High Wind
Watches/Warnings may become necessary further south than they are at
this time, but confidence was too low to warrant them at this time.

Continental Divide Snow:

Snow levels will be rising through Sunday evening, which gives
confidence that snow will largely be above pass level for the bulk
of the next few days. Snow levels do fall enough toward Monday
night into Tuesday for generally light pass level snow along the
Continental Divide, but by then the majority of the precipitation
will be over. Hence, not many impacts are forecast from the snow.

Lower elevation Rain and Potentially Freezing Rain:

Confidence is low in this, but there will be an opportunity for
freezing rain across Southwest Montana valleys that see little
warming over the next couple days. As waves of moisture cross the
Continental Divide into Southwest Montana, air temperatures are
largely forecast to be warm enough for rain at lower elevations.
Areas with frozen ground have an opportunity for freezing rain as a
result. Timing and location of this is very low confidence at this
time, however. Trends will be monitored for changes in confidence.

Additional Strong Winds Tuesday:

Southwesterly winds will turn more westerly during the day Tuesday
and increase in magnitude through the day. Another period of
impactful wind is increasing in likelihood over the entire region,
including southwest Montana valleys. The chance for a 58 mph gust in
Dillon and Ennis Tuesday is around 30%. -AM

&&

.AVIATION...
23/00Z TAF Period

VFR conditions prevail across north-central and southwest MT
terminals through the period under a continued moderate to strong
westerly flow aloft with varying mid to upper level cloudiness.
Main impacts to aviation will be wind related with strong surface
wind/gusts affecting KCTB, KGTF and KEKS and periods of low-level
wind shear affecting primarily SW MT terminals, where surface
winds remain light (KHLN, KBZN) or unaligned with mid-level flow
(KEKS). Mountain wave turbulence will become more widespread
tonight through Sunday as westerly flow strengthens over the
Rockies. Hoenisch

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

&&

.HYDROLOGY...

Warming temperatures through the upcoming work week will lead
changes in river ice conditions and an increased risk of river ice
break-up and the potential of ice jams. Lower elevation snowmelt
and still frozen ground could also lead to some increased runoff
into creeks and rivers, adding to the potential for river ice
breakup. Ice jams are unpredictable and flooding can rapidly
occur, so those with interests along waterways should monitor
water levels over the coming week and take action should flooding
occur.

In addition, frozen ground after a prolonged cold period and
melting snow may result in standing water in areas of poor
drainage. This could create difficult access to fields and impact
some rural roads. As temperatures warm further early next week
and the ground begins to thaw, muddy conditions may create
additional impacts. The greatest risk for overland impacts from
snowmelt look to be from eastern portions of Teton and Pondera
counties across portions of Cascade and Chouteau counties and
most lower elevation areas in Judith Basin and Fergus counties,
where water equivalent in the lower elevation snowpack ranges
from around 1.0" to as much as 3.0 to 4.0" in portions of Fergus
county. These areas are also most susceptible to overnight
temperatures remaining near or above freezing into early next
week. Across southwest MT, there is significant water content in
the snowpack in the Gallatin valley, however melting will likely
be slower with overnight temperatures continuing to fall below
freezing. - Hoenisch

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  40  50  38  49 /   0  10  40   0
CTB  38  47  34  42 /  10  20  40  10
HLN  32  47  35  47 /  10  30  60  10
BZN  25  43  29  46 /   0  10  50  10
WYS  15  34  25  38 /   0  60  90  40
DLN  22  42  29  44 /   0  30  40   0
HVR  33  50  34  47 /  10  20  50  20
LWT  33  47  34  44 /   0  10  40   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Warning until 2 PM MST Monday for East Glacier Park
Region-Eastern Glacier, Western Toole, and Central Pondera-
Northern High Plains.

High Wind Warning from 11 PM this evening to 2 PM MST Monday for
Cascade County below 5000ft-Eastern Pondera and Eastern Teton-
Eastern Toole and Liberty-Judith Basin County and Judith Gap-
Southern High Plains-Southern Rocky Mountain Front-Western and
Central Chouteau County.

High Wind Watch from Sunday evening through Monday afternoon for
Bears Paw Mountains and Southern Blaine-Fergus County below
4500ft-Hill County-Little Belt and Highwood Mountains-Northern
Blaine County-Snowy and Judith Mountains.

High Wind Warning from 8 PM this evening to 2 PM MST Monday for
Madison River Valley.

&&

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