Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 282357
AFDTFX

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

UPDATED AVIATION DISCUSSION

.DISCUSSION...

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.

&&

.AVIATION...
UPDATED 2357Z.
It is a low confidence forecast with details of ceilings and
visibilities. What can be said with confidence is that snow will be
tapering off but do not have much confidence as to when snow will be
ending at any particular taf site. This will have a bearing on the
visibility as when snow ends visibility should generally be VFR. For
KGTF and KLWT am fairly confident that MVFR ceilings and IFR
visibilities in light snow will continue through the night and into
early Monday morning. For KCTB conditions could range anywhere from
IFR to VFR in light snow through Monday morning. Confidence is high
that conditions there will be VFR by Monday afternoon. It is a
similar situation at KHLN and KBZN where conditions could also range
from VFR to IFR in periods of light snow and/or fog through Monday
morning. Have moderate to high confidence that conditions will be
VFR by late Monday afternoon at these latter two sites though some
guidance has MVFR ceilings/visibilities in fog late Monday
afternoon. Blank

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  -7   2 -20   1 /  70  10  10   0
CTB -11  -2 -24   2 /  30  10   0   0
HLN   0   6 -17  -3 /  60  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 /  60  20  10  10
HVR  -1   4 -15   3 /  20  10   0   0
LWT  -4   4 -18   2 /  80  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 from 8 PM this evening to 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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