Helena Valley Northeast, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

670
FXUS65 KTFX 220451
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
951 PM MST Fri Feb 21 2025

Aviation Section Updated.

.KEY MESSAGES...

 - It will gradually warm up through the weekend with windy
   conditions expected through at least Tuesday this has the
   potential to lead to flooding due to river jams and/or snowmelt
   runoff this weekend through at least early next week.

 - The strongest and most impactful wind gusts will be on Sunday
   and Monday with the strongest winds along the Rocky Mountain
   Front.

 - Saturday through Tuesday there will be snow along the Rocky Mountain
   Front and in Southwestern Montana with the greatest amounts in
   Glacier National Park.

&&

.UPDATE...
/Issued 912 PM MST Fri Feb 21 2025/

The main change to the update this evening was increasing the
winds this evening and tomorrow morning. Areas along the Northern
Rocky Mountain Front this evening have had 40 to 50 mph sustained
winds with gusts up to 50-60 mph due to mountain wave activity.
Due to this and blowing/drifting snow from the strong winds, the
High Wind Watch for Saturday morning along the Northern Rocky
Mountain Front got upgraded to a warning (also expanded it to the
Cut Bank area) from tonight through Saturday. After this mountain
wave passes tonight, there may be a small lull in strong winds
until Saturday morning when the pressure gradient tightens.
Blowing and drifting snow can cause severe driving conditions and
greatly reduce visibilities. The high wind watch for the North-
Central MT plains on Sunday look to remain on track, so no edits
were made at this time. -Wilson

&&

.DISCUSSION...
/Issued 912 PM MST Fri Feb 21 2025/

 - Meteorological Overview:

Today there will be upper-level zonal flow across North-central,
Central, and Southwestern Montana. This will keep weather today
similar to yesterday. However due to a slightly stronger pressure
gradient today than yesterday winds will be slightly stronger today
across North-central Montana than yesterday. On Saturday an upper-
level ridge begins to build in across North-central, Central, and
Southwestern Montana. This will allow temperatures across the area
to warm up more. Due to an increase in the surface pressure gradient
and a quick moving shortwave, winds across North-central Montana
will increase more with strong winds along the Rocky Mountain
Front on Saturday. The upper-level shortwave will also bring very
light snow to the Northern Rocky Mountain Front on Saturday. On
Sunday the upper-level ridge remains in place over North-central,
Central, and Southwestern Montana. Strong mid-level flow combined
with an upper-level shortwave and strong surface pressure
gradient will bring strong winds to all of North-central Montana
with very strong winds along the Rocky Mountain Front and Adjacent
Plains on Sunday. The upper-level shortwave will bring very light
snow to Southwestern Montana and snow to the Rocky Mountain Front
on Sunday. On Sunday rain will fall along the Northern Rocky
Mountain Front and Adjacent Plains. Some of this rain could freeze
on contact due to cold ground and road temperatures. See Forecast
Confidence Section for details.

On Monday a quick moving upper-level shortwave trough moves over
North-central, Central, and Southwestern Montana. This combined with
strong upper-level and mid-level flow will bring another round of
windy conditions to much of North-central, Central and Southwestern
Montana with the strongest winds along the Rocky Mountain Front. The
upper-level shortwave will bring another round of snow to the Rocky
Mountain Front and the mountains of Southwestern Montana with a
rain/snow mix across the lower-elevations of Southwestern Montana on
Monday. On Tuesday another quick moving upper-level shortwave moves
through North-central, Central, and Southwestern Montana. This will
bring another round of windy conditions and snow to the Rocky
Mountain Front. The upper-level shortwave will bring another round
of snow to the mountains of Southwestern Montana and a rain/snow
mix to the lower-elevations of Southwestern Montana. Wednesday
through next Friday it will be warm and breezy across much of
North-central, Central, and Southwestern Montana. Due to the warm
temperatures across North-central, Central, and Southwestern
Montana today through next week there will be some localized
flooding and ice jam concerns. See the HYDROLOGY Section below for
more details.

 - Forecast Confidence & Scenarios:

For snow on Saturday there is a 30% chance for an inch or more along
the Rocky Montain Front. For snow on Sunday there is a 50 - 80%
chance for 4 inches of snow or greater along the Rocky Mountain
Front. For snow on Sunday there is a 30 - 50% chance for 2 inches or
greater across the mountains of Southwestern Montana. For snow on
Monday there is a 40 - 60% chance for 2 inches or greater along
the Rocky Mountain Front and in the mountains of Southwestern
Montana. For snow on Tuesday there is a 40 - 60% chance for 2
inches of snow or greater along the Rocky Mountain Front and in
Southwestern Montana. Along the Rocky Mountain Front there is a
10% chance for a hundredth of an inch of freezing rain or greater
from Saturday afternoon through Sunday night.

For wind on Saturday there is a 60 - 90% chance for wind gusts of 75
mph or greater along the Rocky Mountain Front. On Saturday there is
a 60 - 80% chance for wind gusts of 55 mph or greater along the
plains adjacent to the Rocky Mountain Front. For wind on Sunday
there is a 60 - 90% chance for wind gusts of 75 mph or greater along
the Rocky Mountain Front and Adjacent plains. As a result a High
Wind Watch is in effect for the Northern Rocky Mountain Front and
Northern High Plains from 7 AM tomorrow through 11 pm Sunday night.
On Sunday there is a 30 - 80% chance for wind gusts of 55 mph or
greater across much of the rest of North-central Montana. As a
result a High Wind Watch remains in effect from 11 pm Saturday to 11
pm Sunday for much of the rest of North-central Montana except for
the Hi-Line. See the WATCHES/WARNINGS/ADVISORIES below for more
details. For wind on Monday there is a 40 - 80% chance for wind
gusts of 55 mph or greater across most of the lower- elevations of
North- central Montana. On Monday along the Rocky Mountain Front
and Adjacent Plains there is a 50 - 80% chance for wind gusts of
75 mph or greater. For wind on Tuesday there is a 60 - 90% chance
for wind gusts of 75 mph or greater along the Rocky Mountain
Front. Along the plains adjacent to the Rocky Mountain Front there
is a 60 - 80% chance for wind gusts of 55 mph or greater. -IG

&&

.AVIATION...
22/06Z TAF Period

VFR conditions prevail through the TAF period. Gusty west to
southwest winds will increase throughout Saturday morning and
afternoon across the North-Central MT plains. Wind gusts could
gust as high as 45-55kt at times at KCTB. Mountain wave activity
will be a concern through the TAF period, especially along the
Rocky Mountain Front. Light snow will also fall along the
Continental Divide Saturday, but we`re not anticipating
precipitation to spread to the plains. -Wilson

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  37  47  43  51 /  10  10  10  20
CTB  34  45  40  48 /  10   0  10  20
HLN  25  46  34  48 /  10   0  10  30
BZN  17  44  23  44 /   0   0   0  20
WYS  12  33  15  35 /   0  10  10  60
DLN  19  43  23  43 /   0   0   0  30
HVR  27  47  36  50 /   0   0  10  20
LWT  28  46  36  48 /  10   0  10  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Warning until 11 PM MST Saturday for East Glacier Park
Region-Eastern Glacier, Western Toole, and Central Pondera-
Northern High Plains.

High Wind Watch from Saturday evening through Sunday evening for
Bears Paw Mountains and Southern Blaine-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-Northern High Plains-Southern High
Plains-Southern Rocky Mountain Front.

&&

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