005
FXUS65 KTFX 211733
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1033 AM MST Fri Feb 21 2025

Aviation Section Updated.

.KEY MESSAGES...

- Areas of blowing snow and reduced visibility today over North
  Central MT.

- Strong winds develop on Saturday afternoon along the Rocky
  Mountain Front, then spread eastward over the Plains on Sunday.

- Potential for the strong winds to continue over portions of
  North Central MT into Tuesday.

- Accumulating snow will affect areas right near the divide over
  the Northern/Southern Rockies Sun thru Tue.

- Above normal temperatures will be more common across the CWA by
  tomorrow, with the above normal temperatures lasting much of
  next week.

- Small potential for hydro issues over the next several days.

&&

.UPDATE...
/Issued 910 AM MST Fri Feb 21 2025/

It will be warm and windy today across much of North-central,
Central, and Southwestern Montana. Based on MDT and Airport
Cameras, snow has not been blowing along the Rocky Mountain Front
and Adjacent Plains or along the US Highway 87 Corridor between
Great Falls and Lewistown. As a result the Winter Weather
Advisories for those areas were cancelled. Temperatures were
increased across much of North-central, Central, and Southwestern
Montana to better reflect current observations and trends. Wind
speeds and gusts were decreased for today to better match current
observations and trends. The rest of the forecast is on track. -IG

&&

.DISCUSSION...
/Issued 910 AM MST Fri Feb 21 2025/

 - Meteorological Overview:

The start of a few days of more active weather will begin today.
Winds will be increasing this morning, with breezy winds expected
in most areas by the afternoon. There is the potential for areas
of blowing snow/reduced visibility over portions of North Central
MT. However, given the limited blowing snow that occurred on
Thursday, the impact from blowing snow today will be limited.
Additionally, with afternoon temperatures today expected to be
even warmer, the snow should become less blowable by late
afternoon today. Thus the blowing snow advisory was trimmed back
to end at 5 PM today. There is the potential that if temperatures
warm fast enough this morning, combined with sunshine, that this
advisory could be cancelled even earlier. Otherwise, just a few
pockets of colder temperatures remain, with one area being the
Milk River valley. With increasing winds today, everyone should
mix out by late afternoon.

On Saturday, a strong westerly flow aloft will develop over the
CWA. Expect periods of strong winds over North Central MT
starting on Saturday and then continuing into Tuesday. The only
change to the high wind watch area this morning was to start the
Northern High Plains about 12 hours earlier, as winds will pick
up east of the divide a bit sooner. Otherwise the rest of the
watch remains on track. It is likely that a portion of the watch
could be extended into Tuesday, especially over the
northern/western portions.

Right along the divide, the westerly flow aloft will allow for
snow to fall right near the divide. About 5 to 10 inches of
snowfall is expected daily from Sunday thru Tue along the divide.
There is the potential that winter weather statements will be
needed for this area.

The main upper level trof finally moves eastward across the CWA
on Tuesday. This will bring an end to the strong winds, but also
allow for a chance for rain/snow to move eastward across the CWA.
Temperatures on Tuesday will be tricky, as they will likely cool
behind the trof, so some adjustments to forecast highs might
occur over the next few days.

An upper level ridge is then forecast to build over the CWA by
late next week, resulting in a drier/warmer conditions returning
to the CWA.


 - Forecast Confidence & Scenarios:

Overall the main concern Sat thru Tue will be strong winds over
portions of North Central MT and snow along the divide. Right now
there is up to an 90 percent chance of wind speeds reaching
warning criteria around Cut Bank by Sunday, and near a 60 percent
chance around Great Falls.

In terms of snow, there is a 70 percent chance for 4 inches or
more of snow daily from Sun thru Tue right near the divide, with
the most favored area being the Northern Rockies. Brusda

&&

.AVIATION...
21/18Z TAF Period


VFR conditions prevail across north-central and southwest MT
through the TAF period. Except for some lower cloud and terrain
obscuration near Yellowstone NP and along northern portions of
the continental divide, mainly clear skies at terminals will give
way to increasing mid to higher level clouds late this afternoon
through tonight. Mid-upper level flow across the Rockies turns
from the NW to W and strengthens later today through tonight for
an increasing risk of mountian wave turbulence. Gusty west to
southwest surface winds develop today at KGTF and KCTB with gusts
to around 30kts later this afternoon, increasing to 35-45kts late
tonight through Saturday. Hoenisch


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

&&

.HYDROLOGY...

Warming temperatures through the weekend and 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 this weekend 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  34  46  40 /   0  10   0  10
CTB  39  31  44  35 /   0   0   0  20
HLN  42  26  45  33 /   0   0   0  10
BZN  34  14  39  23 /   0   0   0   0
WYS  29  10  32  17 /   0   0  10  10
DLN  34  19  38  24 /   0   0   0   0
HVR  37  25  43  33 /   0   0   0  10
LWT  40  27  43  34 /   0   0   0  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Watch from Saturday afternoon through Sunday evening
for Northern High Plains.

High Wind Watch from Saturday evening through Sunday evening for
Cascade County below 5000ft-East Glacier Park Region-Eastern
Glacier, Western Toole, and Central Pondera-Eastern Pondera and
Eastern Teton-Judith Basin County and Judith Gap-Southern High
Plains-Southern Rocky Mountain Front.

&&

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