Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 271602
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
902 AM MST Sat Dec 27 2014

.UPDATE...

Increased PoPs over the plains this morning as flurries and light
snow showers begin to develop with a weak upper-level shortwave.
Any snow accumulation will be less than an inch this morning,
before the main storm system and widespread accumulating snowfall
develop by late this evening. Breezy west-southwest winds are
expected today, which could also lead to localized areas of
blowing and drifting snow. The remainder of the forecast is on
track so made no further changes. MLV

&&

.AVIATION...
UPDATED 1145Z.
Areas of fog this morning in and around KBZN should dissipate after
sunrise. Elsewhere, mid and high clouds continue to increase as
moist northwest flow aloft persists. An approaching weather system
from the west will begin impacting the Rocky Mountains after 18z as
snow and blowing snow develops. Snow will spread out onto the plains
by 00z and become widespread thereafter. Increasing winds will also
produce areas of blowing snow during the evening hours. VFR
conditions prevail. Increasing MVFR/IFR conditions after 00z due to
snow and low ceilings. Mountains becoming increasingly obscured
after 18z.

&&

.PREV DISCUSSION...
/ISSUED 445 AM MST Sat Dec 27 2014/
Saturday through Monday...A low pressure system moves into the
Pacific Northwest today and begins to impact Montana tonight into
Sunday. Snow moves towards the Continental Divide from the west-
northwest and looks to begin falling across Central Montana by
this evening. Expect a fairly similar event compared to the last
storm with the exception of much colder temperatures in the wake of
this event. Snow totals over a two day span look very similar to the
last storm with amounts highest over the northern Rockies and
adjacent plains. Expect strong winds into tonight in this region so
blowing snow reducing visibility will also be a concern. A Winter
Storm Warning was issued for this area based on these expected
conditions. Central and Southwest Montana look to see less snow
overall so only a Winter Weather Advisory is in effect. The best
period for seeing heavy snowfall looks to be from tonight into
Sunday. Most moisture exits the region by early Monday but some
light snow showers may linger into Monday evening. Temperatures may
reach freezing in some locations today but will significantly drop
into next week.

Monday night through Saturday...Medium range period begins with
scattered light snow ending over the area as the upper trof
responsible for the snow continues to push south and away from the
area. A strong upper ridge builds over the eastern Pacific on
Tuesday and Wednesday resulting in a northerly flow over the area
that will be dry and cool. The only precipitation will occur over
the Northern Rocky Mountain Front. By Thursday, shortwave energy
will begin to rotate south out of western Canada and will spread
light snow across the Hi-Line. Moisture and upslope lift associated
with the shortwave will result in widespread light snow developing
Friday across the area which will continue through Saturday. The
coldest temperatures will occur Tuesday morning with readings
generally in the teens below zero and highs reaching only the single
digits above zero during the afternoon. Temperatures will slowly
moderate during the week though readings will remain below seasonal
averages. By the end of the week, another round of cooler air will
push across the border from Canada.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  29  15  22  -9 /  20 100 100  60
CTB  28  10  15 -15 /  20 100 100  30
HLN  25  17  22  -2 /  20 100 100  40
BZN  19  11  22  -5 /  20 100 100  60
WEY  18   9  24 -10 /  60  90 100  60
DLN  24  11  24  -1 /  20 100 100  40
HVR  31  16  19  -6 /  20  90 100  30
LWT  30  15  23  -6 /  20  90 100  60

&&

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

WINTER WEATHER ADVISORY from Noon today to 6 AM MST Monday
Cascade...Central and Southern Lewis and Clark...Chouteau...
Eastern Glacier...Eastern Pondera...Eastern Teton...Fergus...
Judith Basin...Meagher...Toole.

WINTER STORM WARNING from Noon today to 6 AM MST Monday Northern
Rocky Mountain Front...Southern Rocky Mountain Front.

&&

$$

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