Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 261158
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
455 AM MST Sun Jan 26 2020

...UPDATED AVIATION SECTION...

.SYNOPSIS...

A Pacific cold front will bring scattered rain and snow showers
to the region later this afternoon through tonight. Coverage will
be more widespread over southwest Montana, which will likely bring
measurable snowfall down to the valley floors. Breezy westerly
winds with decreasing cloudiness are on tap for Monday in the wake
of the cold front, but chances for precipitation return Tuesday
through Wednesday. Overall, temperatures should remain above
normal. Winds could become quite strong starting Friday and
continuing through the weekend, bringing even warmer temperatures.

&&

.DISCUSSION...

Today through Monday Night...

A shortwave trough is on track to bring precipitation to the
forecast area later today through tonight, but the latest
forecast models are slowing its movement somewhat. (This is
likely due to the high pressure ridge ahead of it being quite
strong and amplified, which is hindering the eastern movement of
the shortwave.) Precipitation will now move into the mountains of
western and southwest Montana more so this afternoon and across
the forecast area tonight into Monday morning with an associated
Pacific cold front. Snow is likely in the mountains throughout
this time, while scattered showers over the plains will be more
so in the form of rain, possibly mixing some snow later tonight.
The main energy associated with this system will move over
southwest Montana, especially along and south of Interstate 90.
Again, precipitation there will start off as a mix of rain and
snow showers, but it should transition to all snow early this
evening, causing the accumulation of snow in the valleys.
(Note: There is a slight chance of freezing drizzle in the West
Yellowstone and Centennial valleys as precipitation begins there
late this morning into early this afternoon due to cold air -
along with low clouds - trapped there.) Snowfall amounts in the
mountains along the Continental Divide and in central Montana will
be somewhat light - mostly 1 to 3 inches, but up to 6 inches
possible in the mountains of Glacier National Park. However, south
of I-90, snow amounts in the valleys still look to be in the 1 to
3 inch range, with 4 to 8 inches in the mountains. Will therefore
continue the Winter Weather Advisory there. Snow will move east of
the area on Monday with the cold front, and breezy westerly
downslope winds will help decrease the cloudiness. Overall,
though, temperatures will remain 5 to 10 degrees above normal.
Coulston

Tuesday through next Sunday...

Two more shortwave troughs, similar to the one moving through
today and tonight, are forecast to move through Montana
Tuesday/Tuesday night and Wednesday/Wednesday night. However,
these disturbances will be in more of a northwest flow aloft and
will be fairly fast-moving with continued mild temperatures, so
significant snowfall amounts are unlikely at this time.
Regardless, much of the area could see some light precipitation
during this time. After Thursday, a broad high pressure ridge will
build into the southwestern United States, putting Montana under
more of a westerly flow aloft. This will bring breezy westerly
downslope winds to much of the forecast area, which will limit any
additional precipitation to the mountains. However, these winds
will help warm temperatures further (highs mostly in the 50s at
lower elevations with above freezing lows). Winds during this time
could become quite breezy at times, so will monitor for potential
High Wind highlights.
Coulston

&&

.AVIATION...

Updated 455 AM MST Sun Jan 26 2020 (26/12Z TAF Period)

North Central and Central Montana (KCTB, KHVR, KLWT, KGTF, KHLN):
VFR conditions are expected to prevail through at least the next 24
hours. Skies will remain mostly clear through around 18Z with
decreasing mid clouds (between 6000 and 8000 feet agl) from KCTB
through KGTF to KLWT. Areas of fog/low clouds should stay to the
north and east of KHVR through 16Z before shifting east, but there
is a chance that it may move into the KHVR area for a brief time
through then. A disturbance will then bring mid and high clouds to
the area after 18Z. Scattered rain and snow showers with an
associated cold front will obscure mountains, as well as bring
periods of MVFR conditions to KHLN/KGTF/KCTB between 00Z and 04Z and
to KHVR and KLWT after 04Z. Breezy westerly downslope winds will
then develop  along the east slopes of the Rockies after 05Z.

Southwest Montana (KBZN, KEKS, KWYS): Mid and high clouds will
increase here through 18Z with the approach of the cold front, but
MVFR/IFR conditions will likely persist at KWYS due to low cloud
advection from southeast Idaho, and periods of MVFR conditions are
possible at KBZN. The front will then bring widespread mountain
obscuration in low VFR/MVFR conditions with rain/snow showers after
19Z, then widespread MVFR/IFR conditions in snow after 00Z.
Coulston

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  44  31  46  30 /  10  30   0   0
CTB  40  29  43  26 /  10  10   0   0
HLN  42  29  44  26 /  30  50  10   0
BZN  44  27  44  24 /  40  90  30   0
WYS  34  18  31  15 /  80  90  50  20
DLN  38  24  37  23 /  80  80  10   0
HVR  37  25  43  25 /   0  20  10   0
LWT  43  28  45  26 /   0  40  20   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from noon today to 5 AM MST Monday
Beaverhead...Gallatin...Madison.

&&

$$

http://www.weather.gov/greatfalls



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