Area Forecast Discussion
Issued by NWS Great Falls, MT

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
199
FXUS65 KTFX 160255
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
755 PM MST Thu Feb 15 2018

.SYNOPSIS...

Winds will begin to increase along the Rocky Mountain Front this
evening, overspreading the remainder of the plains overnight.
Strong winds along the northern Rocky Mountain Front will result
in blowing and drifting snow with blizzard conditions along and
west of highway 89. Drifting snow will impact the rest north
central Montana as winds increase. Temperatures will slowly rise
into the teens though the night in the plains. Lows will fall
into the single digits and teens over the valleys. &&

.EVENING UPDATE...

Latest surface analysis and observations indicate the stronger winds
remain confined right along the Rocky Mtn Front at this hour. With
time, though, we still expect a tightening pressure gradient to
allow stronger winds to develop further out over the plains. Until
that time, though, mostly clear skies and a good snowpack are
allowing temps to fall faster than originally forecast in several
areas, especially Cut Bank to Great Falls to Lewistown. For this
evening, then, the main change was to lower temps this evening
before the increasing wind allows rising temps the remainder of the
night. Along the Rocky Mtn Front, winds have been a bit slower to
increase and webcams in the area suggest significant
blowing/drifting of snow has yet to begin. However, an increasing
trend has been noted in wind gusts in this area and more widespread
blowing/drifting should begin shortly. For now, we will leave the
Blizzard Warning as is, but will closely monitor conditions through
the night to determine if any changes are needed. Elsewhere, the
Winter Weather Advisory for snow and blowing snow still looks good.
The greatest impacts from blowing/drifting snow will likely be where
the heaviest fresh snow fell yesterday/last night. Of note,
blowing/drifting may hold off until a bit later overnight or even
until Friday morning. Even so, we`ll keep the current start times as
is. MARTIN

&&

.AVIATION...
Updated 2350Z.

System that brought snowfall to the region earlier today has moved
out of Montana leaving mostly clear skies and VFR conditions.
However, the next system will begin to send mid- and high-level
clouds over the forecast area this evening with cloud heights
lowering after 12Z as areas of light snow and mountain obscurations
develop from west to east. Also, westerly surface winds will
increase overnight producing areas of blowing and drifting snow
along with low level wind shear and turbulence aloft. mpj

&&

.PREV DISCUSSION...
/ISSUED 450 PM MST Thu Feb 15 2018/

An active weather pattern will continue across the region though the
weekend resulting in several periods of impactful weather.

Tonight though Friday night...
The cold airmass will begin to retreat to the east tonight as a
trough of low pressure forms along the lee side of the northern
Rockies. This will result in increasing winds starting over the
Rocky Mountain Front this evening and spreading east into the
plains through the overnight hours. These winds will result in
widespread blowing and drifting snow over north central Montana
with blizzard conditions along and west highway 89 from the Heart
Butte area up to Browning and Babb. Across the remainder of north
central Montana restricted visibilities are possible but the
biggest impacts will be from snow drifting across roadways.

A cold front will sweep though the area Friday evening with winds
shifting north and gradually decreasing. Heavy snow will impact the
higher elevations of the Rocky Mountain Front with several inches
of snowfall expected. Over the plains and valleys a brief band of
moderate to heavy snow will be possible with the passage of the
cold front resulting in quick snow accumulations of 1 or 2 inches.

Saturday though Sunday morning...
Pacific moisture will begin to overrun the cold airmass resulting
in the development of moderate to heavy snow over north central
Montana on Saturday afternoon. An arctic cold front will push
south into the area Saturday night bringing additional moderate to
heavy snowfall. Heavy snow accumulations approaching a foot are
possible in a band over north central Montana. Models solutions
diverge with the placement of the heaviest snowfall. Took a
blended approach to the snow totals, which is heavily based on the
National Blend model output. Forecast snowfall totals will likely
change as the event nears.

Sunday afternoon though Monday...
Widespread light snow is likely but the main impacts will be from
dangerously cold wind chills falling into the 20s and 30s below
zero over north central Montana. Southwest Montana will likely
remain warmer until Sunday night when the arctic airmass works its
way southward.

Monday night though Thursday...
After a very cold start to the day on Tuesday temperatures will
slowly moderate though the week but remain below average for most
locations. A few periods of light snow will be possibly though the
late week.

Langlieb

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  -6  35  11  28 /  10  60  80  70
CTB   1  32   5  19 /  10  60  80  70
HLN   9  32  16  33 /   0  50  70  70
BZN   6  29  15  34 /   0  60  90  60
WEY   8  26  12  28 /  20  90  80  70
DLN  13  29  18  37 /  10  40  50  40
HVR  -3  30   5  18 /   0  50  30  50
LWT   0  29  10  28 /   0  60  80  60

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 11 PM this evening to 5 AM MST
Saturday Blaine...Chouteau...Fergus...Hill...Liberty.

Winter Weather Advisory until 5 AM MST Saturday Cascade...Judith
Basin...Meagher.

Blizzard Warning until 6 AM MST Friday Northern Rocky Mountain
Front.

Winter Weather Advisory until 5 AM MST Saturday Central and
Southern Lewis and Clark...Eastern Glacier...Eastern Pondera...
Eastern Teton...Southern Rocky Mountain Front...Toole.

Winter Weather Advisory from 6 AM Friday to 5 AM MST Saturday
Northern Rocky Mountain Front.

&&

$$

http://www.weather.gov/greatfalls



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.