Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 290535
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1035 PM MST Sun Dec 28 2014

.UPDATE...
Increased pops this evening and into the early morning hours to
better account for the lingering snow showers across the area.
Have left temperatures alone for the most part. Blowing
snow has also been included in the weather grid through the
overnight hours. Otherwise no significant changes to the forecast
this evening. Suk

&&

.AVIATION...
UPDATED 0535Z.
Widespread IFR visibilities and MVFR ceilings in snow will continue
from KCTB to KGTF to KLWT to KHLN into Monday morning. During the
afternoon or early evening conditions should improve to VFR as snow
ends. For KBZN and KHVR conditions should be generally VFR though
there could be a short period of MVFR conditions in snow the rest of
Sunday night. For these two sites some guidance indicates that
ceilings and visibilities could lower to MVFR later Sunday night and
continue through Monday morning but did not think this was enough of
a threat to mention in the tafs. Widespread mountain obscurement
will continue over the forecast area at least through Monday
morning.  Blank

&&

.PREV DISCUSSION...
/ISSUED 457 PM MST Sun Dec 28 2014/

Tonight through Tuesday...A band of moderate to heavy snow
developed early this afternoon over areas from Augusta to
Raynesford with snowfall rates 1 to 2 inches per hour. As of 3
pm, this band was beginning to weaken. Snow will gradually taper
from north to south this afternoon and evening. Additional snow
accumulations through midnight will be up to 2 inches over the
plains and 2 to 4 inches in the mountains. Winds will remain
steady tonight with north winds 10 to 20 mph and gusts up to 25
mph at times. The combination of falling snow and gusty winds will
create widespread blowing and drifting snow with near whiteout
conditions at times. Have continued current winter weather
highlights through Monday morning. As temperatures fall into the
single digits this evening and below zero overnight, wind chills
of 20 to 35 below zero will be likely and have issued a Wind Chill
Advisory for most of north-central Montana beginning this evening
and continuing through Monday. Winds will be lighter in southwest
Montana, however wind chills may be near 20 below at times.

As a strong area of surface high pressure builds into north-
central Montana Monday night and Tuesday, winds will decrease, but
overnight temperatures will be very cold. Clearing skies, recent
snow and light winds will promote overnight lows Tuesday morning
around 20 to 25 below for many areas with bitterly cold wind
chills near 40 below at times. Highs on Tuesday will be around 0.
MLV

Tuesday night through Sunday...The medium range period begins with a
strong upper ridge over the eastern Pacific and a closed upper low
over northern California/western Nevada. The resulting northerly
flow aloft over the area will be dry but cool and will continue
through Wednesday. By Thursday, weak shortwave energy rounding the
top of the upper ridge, along with a plume of moisture, will bring
light snow to the Hi-Line. Pacific moisture will override the cool
air-mass east of the Continental Divide on Friday resulting in a
large area of snow that will continue into Saturday. Another push of
cold air into the area Sunday will allow scattered snow showers to
continue. Temperatures will remain well below seasonal averages.
Lows Saturday and Sunday will be below zero for most of northern and
North Central Montana. GFS model hinting at very cold readings
Monday morning.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  -7   2 -20   1 /  90  10  10   0
CTB -11  -2 -24   2 /  70  10   0   0
HLN   0   6 -17  -3 /  80  20  10   0
BZN  -5   9 -19  -4 /  90  20  10   0
WEY  -5  14 -20   5 /  90  40  20  10
DLN   1  10 -13   1 /  80  20  10  10
HVR  -1   4 -15   3 /  40  10   0   0
LWT  -4   4 -18   2 /  90  20  10  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY until 6 AM MST Monday Beaverhead...
Blaine...Broadwater...Cascade...Central and Southern Lewis and
Clark...Chouteau...Eastern Glacier...Eastern Pondera...Eastern
Teton...Fergus...Gallatin...Hill...Jefferson...Judith Basin...
Liberty...Madison...Meagher...Toole.

WIND CHILL ADVISORY until 6 PM MST Monday Blaine...Cascade...
Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...
Fergus...Hill...Judith Basin...Liberty...Northern Rocky Mountain
Front...Southern Rocky Mountain Front...Toole.

WINTER STORM WARNING until 6 AM MST Monday Beaverhead...Northern
Rocky Mountain Front...Southern Rocky Mountain Front.

WINTER STORM WARNING until 6 AM MST Monday FOR ELEVATIONS ABOVE
6000 FEET FOR Cascade...Judith Basin...Meagher.

&&

$$

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