Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 220408
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
908 PM MST Sun Dec 21 2014

.DISCUSSION...
Update forthcoming. Have lowered temperature tonight for Great
Falls given the clearing that has occurred. Moist northwest flow
aloft will continue over the area. Enough instability present to
maintain scattered snow showers, especially over the mountains. To
that end, will continue with the winter weather advisory
highlights as current radar returns still indicating some light
snow occurring at elevation. Winds continue to decrease though
some areas will continue to see gusty conditions until midnight.
Northwest flow aloft continues Monday with lingering isolated
mountain snow showers and mixed rain and snow showers over the
plains.

&&

.AVIATION...
UPDATED 2330Z.
Strong/moist northwest flow aloft will continue over the region
through Monday. Occasional snow showers and widespread terrain
obscurations will continue over the western and southwest MT mtns
tonight through Monday as several embedded weather disturbances move
through the NW flow aloft. Most aviation terminals however will
remain VFR with only isolated showers in the vicinity. Strong winds
and Mtn wave turbulence will gradually subside tonight as main core
of strongest wind aloft sags to the south of the region, however
gusty surface winds will continue through Monday. Hoenisch

&&

.PREV DISCUSSION...Issued 311 PM MST Sun Dec 21 2014

Tonight through Tuesday...Upper level shortwave trough axis
crossed the Continental Divide Sunday along with its attendant
surface front. Surface pressure rises behind the front and
thinning seen on satellite water vapor imagery marked strong
subsidence behind the wave. Wind gusts exceeded 60 mph at several
locations along the Rocky Mountain Front. A High Wind warning
continues for this area through 00Z...and will be evaluated for
possible extension. Meanwhile, strong wind gusts appeared further
south, extending along a line from Helena to Lewistown. Broadwater
and Meagher counties were added to the High Wind Warning through
10pm MST. Winds are expected to taper overnight.

Snowfall amounts today were generally 2-6 inches as forecast over
mountain passes, with higher amounts above pass level. The stream
of Pacific moisture has shifted south of Montana, but a strong and
unsettled northwesterly flow will continue to generate orographic
mountain snow showers through the night. An additional 1 to 3
inches of snow is possible tonight over mountain passes with 3 to
6 inches above pass level. Winter Weather advisories continue. All
precipitation tapers to an end Monday...lingering through mid day
over the far southwest Mountains. High pressure settles over the
region for a fair weather day and good travel conditions. Nutter

Tuesday night through Sunday...Expect another Pacific storm system
to move through the region from Tuesday night through Christmas Day.
Precipitation will be light to start with Tuesday night into
Wednesday morning...but will pick up in intensity by late Wednesday
afternoon through Christmas morning. It still looks like the swath
of heaviest snowfall will fall west of a line from Cut Bank to
Lewistown...with the Havre area only seeing around an inch of snow.
Otherwise...overall total snow accumulations still look to be on
track from previous forecasts...with a slight increase in the
mountains. Thus a generally 2 to 5 inches is expected at lower
elevations and 6 to 12 inches is expected in the mountains. Isolated
amounts around 16 inches will be possible in the mountains.
Temperatures will be mild Wednesday morning...but will fall rather
quickly Wednesday afternoon as colder air moves into the region
changing any rain back over to snow. For Friday and Saturday...it
will generally be cold with just a passing snow shower from time to
time. For Sunday and into early next week...the GFS13 and EC are
quite different. The EC model wants to start slowly warming things
up with little precipitation...while the GFS13 wants to bring down
significantly colder air and a better chance for precipitation. For
now I will go in the middle...but changes in the forecast are likely
to occur for this time period once model agreement starts to become
a bit more clear. Brusda/MPJ

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  28  39  20  37 /  10  20  10  10
CTB  28  37  21  35 /  10  20  10  20
HLN  29  38  18  33 /  30  20  10  10
BZN  24  34   9  26 /  40  30  20  10
WEY  22  31   5  27 /  90  40  20  10
DLN  28  35  12  31 /  60  30  10  10
HVR  27  39  20  37 /  30  20  20  10
LWT  29  38  20  37 /  40  30  20  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY until 5 AM MST Monday FOR ELEVATIONS
ABOVE 5000 FEET FOR Central and Southern Lewis and Clark...
Jefferson...Northern Rocky Mountain Front...Southern Rocky
Mountain Front.

WINTER WEATHER ADVISORY until 5 AM MST Monday FOR ELEVATIONS
ABOVE 5500 FEET FOR Beaverhead...Broadwater...Cascade...
Gallatin...Judith Basin...Madison...Meagher.

&&

$$

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