Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 262148
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
248 PM MST Fri Dec 26 2014

...WIDESPREAD SNOW...BLOWING SNOW AND CONTINUED TRAVEL IMPACTS THIS
WEEKEND...

...MUCH COLDER TEMPERATURES EARLY NEXT WEEK...

.DISCUSSION...

Tonight through Sunday...Light snow has generally ended across the
area this afternoon as a weak upper-level shortwave continues to
move south. Quiet weather is expected overnight before a vigorous
storm system pushes into the Northern Rockies this weekend. Ample
lift and moisture associated with this system will lead to widespread
snow and much colder temperatures for north-central and southwest
Montana with continued travel hazards and impacts likely. Snow
will begin pushing into higher terrain along the Rocky Mountain
Front by midday Saturday and then spread east into the north-
central plains by late Saturday afternoon and evening. Snow will
reach southwest Montana late Saturday night or Sunday morning.

The main period of heaviest snowfall will be Saturday night
through midday Sunday and snow will end by Monday morning. In
addition to snow, gusty north winds of 10 to 20 mph with gusts to
30 mph, mainly on Saturday and Sunday afternoons will create areas
of blowing and drifting snow. Total snowfall amounts in higher
elevations at and above pass level along the Continental Divide
and central mountain ranges will range from 6 to 12 inches with 3
to 6 inches in lower elevations below pass level. Given this
combination of snow and blowing snow, travel could be very
hazardous and have issued a Winter Storm Watch beginning Saturday
afternoon. Over southwest Montana, valleys can expect 2 to 5
inches of snow with 5 to 10 inches in the mountains above pass
level. Have issued a Winter Weather Advisory beginning Saturday
night for areas over southwest Montana. Lesser snow amounts of 1
to 3 inches are expected for areas east of I-15 and north MT-200,
which includes the Hi-Line. The cold airmass will generally follow
the snow with temperatures steadily falling into the teens and
single digits during the day on Sunday. MLV

Sunday night through Friday...The period begins with a broad upper
trof continuing to impact the area with widespread light snow.
Conditions improve on Monday though isolated snow showers will
linger through the afternoon. By Tuesday and Wednesday, a strong
upper ridge will build over the eastern Pacific placing the area
under a cool, but generally dry, northerly flow aloft. Snow showers
will be confined to the western mountains. An upper trof will swing
south out of Canada on Thursday and bring the possibility of
scattered snow to the Hi-Line during the afternoon. By Friday, the
trof will deepen and push further south and west. Scattered snow
will become more widespread Friday afternoon. Temperatures will be
well below seasonal averages to start the period with Tuesday
morning likely being the coldest morning with readings in the teens
below zero many areas. Temperatures will slowly warm by the end of
the period though readings will generally remain below seasonal
averages.

&&

.AVIATION...
UPDATED 1718Z.
A weak disturbance moving through the northwest flow aloft will move
through Central Montana Southwest Montana this afternoon and exit
the region this evening. Areas of light snow associated with this
feature will generally cause local MVFR conditions although some IFR
is possible. Conditions will dry tonight although another weak
disturbance will create MVFR/IFR conditions again Saturday.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  11  29  14  19 /   0  40 100  90
CTB  11  29  10  11 /   0  30 100  90
HLN   9  25  16  20 /   0  20 100 100
BZN  -3  19  11  21 /   0  20 100 100
WEY  -6  17  10  24 /   0  60  80  80
DLN   4  23  11  23 /  10  20 100 100
HVR  15  31  14  18 /   0  10  60  70
LWT   9  29  15  21 /   0  10  60  80

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY from 6 PM Saturday to 6 AM MST Monday
Beaverhead...Broadwater...Gallatin...Jefferson...Madison.

WINTER STORM WATCH from Saturday afternoon through late Sunday
night Cascade...Central and Southern Lewis and Clark...
Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...
Fergus...Judith Basin...Meagher...Northern Rocky Mountain
Front...Southern Rocky Mountain Front...Toole.

&&

$$

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