Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 011141
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
441 AM MST Thu Dec 1 2016

.UPDATE AVIATION...

&&

.DISCUSSION...

Today through Saturday...A weak upper level low will push across
the region today...bringing with it periods of light to moderate
snow. Snow will initially begin across the west and south...with
some lingering light snow across the north through the morning
hours. As this low progresses south and eastward throughout the
day...so will the chances for snow. By this evening models
indicate light to moderate snow possible from the Rocky Mountain Front
to Choteau to Winifred and south. Some models even indicated the
Great Falls area could get a short blast of light to moderate snow
from about 5 PM to around midnight tonight. These models are
picking up on some unstable cold air aloft with a little bit of
upslope northerly flow component. This may need to be watched for
further expansion of the current Winter Weather Advisories. These
advisories continue to be in effect along the Rocky Mountain Front
to portions of central and southern Montana. Snow accumulations
with this system won`t be overly high...with generally 1 to 4
inches expected...however...some impacts to travel are possible.
Snow then diminishes Friday morning as a brief ridge of high
pressure begins to build overhead. By Friday afternoon...any
chances for snow are confined to the Rocky Mountain Front. This
ridge then quickly breaks down Friday night into
Saturday...sending quick and moist westerly flow to the region.
Initially snow will be confined to the mountains and southern
portions...however...moisture streaming in combined with a weak
disturbance and front could bring slight chances of widely
scattered light snow...and rain...through the day Saturday to
central and eastern portions. Models showing not as much coverage
for Saturday as previous runs...so lowered pops
slightly...especially in the north and central. Also little snow
accumulation will be possible for the lower elevations...with some
light to moderate accumulations possible in the mountains by days
end. Other item to watch on Friday night through Saturday will be
the potential for strong winds. Tonight`s models are showing less
winds at the 700 mb level...however...gusts could still be in the
30 to 40 knot range...with higher readings along the Rocky
Mountain Front. Not quite High Wind Warning Criteria...but still
quite windy. Temperatures will be at near normal readings through
much of the short term...with 40s possible by Saturday. Anglin

Saturday night through Wednesday...Models continue to depict a
significant change in the overall weather pattern to evolve late
this weekend through early next week as an upper level trough digs
from the Gulf of AK/Western Canada south into the western and
eventually central US. Models are also coming into better agreement
on the details of how this system evolves with a fast/moist Pacific
Jet streaming across the Northern Rockies Saturday night and Sunday
as the upper trough moves into western Canada. This looks to focus
an increasing amount of orographic enhanced precipitation over the
western MT Mtns with significant snow likely along northern portions
of the continental divide in the Bob Marshal/Glacier Park areas.
Windy conditions are also likely Sat night through Sunday for much
of the forecast area with the potential for strong winds existing
across western portions of north-central MT. Westerly winds
will limit snow chances for areas east of the continental
divide Saturday night and Sunday. Expect snow to become more
widespread across the entire forecast area late Sunday through
Sunday night as a shortwave moving through the base of the deepening
western Canada trough crosses the northern Rockies with a surface
low emerging across central/eastern MT by Monday morning. This
scenario would favor portions of north central MT for some moderate
snow amounts of several inches through Monday morning with a colder
airmass beginning to filter in behind the surface low Sunday night
through Monday morning. Cold surface high pressure with origins in
the Arctic then noses southward east of the Rockies through the day
Monday for falling temperatures with snow becoming less widespread.
The much colder airmass looks to spread south and settle across the
entire forecast area Monday night through Wednesday with daytime
temperatures Tuesday/Wednesday likely only in the single digits and
teens with some areas seeing subzero temperatures Tues/Wed morning.
Confidence is growing in the potential for multiple winter weather
hazards during the Sunday though early next week period with more
specific details likely to emerge over the following days. Hoenisch

&&

.AVIATION...Updated 1200Z.

An upper level disturbance will bring periods of snow...and MVFR
to IFR conditions across the forecast area today. Snow is mainly
expected across western and southern MT this morning affecting
KBZN and KEKS...with some isolated snow showers in the north near
KHVR. As this disturbance moves across the state later
today and into this evening...light snow could affect all area
TAF sites...with MVFR to IFR conditions possible at times. Some
models indicate locally moderate snow is possible at times this
evening into the early overnight hours...especially near
KGTF...KHVR...and KLWT areas. These sites could see LIFR if any
heavier snow showers can develop this evening. Expect mountain
obscuration along the Continental Divide and in southwest MT due
to widespread cloud cover and periods of snow during the forecast
period. Anglin

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  37  23  35  29 /  40  60  10  20
CTB  35  21  32  29 /  30  30  10  20
HLN  37  20  38  25 /  30  30  10  20
BZN  33  20  31  21 /  40  40  20  30
WEY  26   3  24   8 /  40  30  20  30
DLN  32  14  29  19 /  30  30  10  20
HVR  35  21  33  27 /  30  30  10  30
LWT  37  23  33  24 /  30  50  20  30

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 5 AM MST Friday Beaverhead...
Broadwater...Central and Southern Lewis and Clark...Gallatin...
Jefferson...Madison...Northern Rocky Mountain Front...Southern
Rocky Mountain Front.

Winter Weather Advisory until 5 AM MST Friday Cascade...Judith
Basin...Meagher.

&&

$$

weather.gov/greatfalls


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