Special Weather Statement, NWS Great Falls, MT

Area Forecast Discussion
National Weather Service Great Falls MT
245 PM MST Wed Feb 14 2018

.SYNOPSIS...

A storm system moving southeast from British Columbia will spread
snow across the northern Rockies and Montana tonight behind a
fast moving cold front surging south from Alberta. A much colder
airmass will move south into the area as well with a period of
gusty north winds creating areas of blowing and drifting of the
new snow tonight into early Thursday morning. A brief and
temporary return to seasonal temperatures is expected Friday along
with gusty southwest winds before another cold and unsettled
period develops this weekend, which may last into early next week.

&&

.DISCUSSION...

Today through Friday...Canadian cold front has moved through Cut
Bank this afternoon and is expected to rapidly surge south into
central MT by early this evening. Ahead of the front, the airmass
has become marginally unstable with scattered bands of
precipitation developing this afternoon, but a more cohesive band
of snow is expected to drop south along and behind the cold front
later this afternoon and evening. Behind the initial frontal band
of precipitation, which pushes into SW MT later tonight, moist
northerly upslope flow will maintain lighter snow across southern
and western portions of north-central MT. Strong pressure rises
behind the front are bringing gusty north winds of around 30kts
to SW AB this afternoon and similar gusts are likely to follow the
frontal passage through n-central MT this evening, leading to
some areas of blowing and drifting snow. Total snow accumulation
forecasts have changed little with a winter weather advisory in
effect for all but far SW portions of the forecast area with
widespread accumulation of 2 to 4 inches by Thursday morning with
higher amounts in the mountains. Much colder airmass settles over
the region later tonight through Thursday with temperatures in the
single digits to low teens. Lee-side trough develops fairly
quickly behind the exiting system and surface high Thursday night
through Friday with temperatures warming back to seasonal averages
under gusty southwest winds before the next round of cold and
potentially snowy conditions arrive this weekend. Hoenisch

Friday night through Tuesday...NW flow looks to dominate the weather
pattern over the weekend, eventually transitioning to a broader
Western US trough by early next week. This should allow the
unsettled conditions of late to continue, especially in
the more recently favored areas along/north of I-90.

The main focus revolves around a quick-moving system later Friday
into Saturday followed by potentially a more significant snowfall
later Saturday into Sunday. The storm track during this time looks
very similar to what we have seen over the past few weeks (ie. the
heaviest snowfall and coldest temps being focused over Central MT
with lesser amounts and not as cold temps further south). The
FRI/SAT system, quick as it may be, could produce a brief period of
heavier snow focused in/around the central mountains. After a brief
lull, a more widespread snow will likely develop later Saturday into
Sunday before tapering off on Monday. The models differ on where the
greatest lift/snowfall will be, but the potential exists for another
widespread 4-8 inches over the plains, 2-5 inches for SW valleys,
and 6-12 inches in the mountains. Exact amounts will be refined as
models, hopefully, come into better agreement regarding where the
best lift will be focused. As we have seen in recent events, there
is some potential for focused/heavier snow bands to develop, but
again, too early to know where that may occur. In the wake of the
weekend system, the trough in place should keep temps on the cold
side, although a lack of a stronger surface high may help keep the
very cold thickness values from being realized at the surface.
MARTIN

&&

.AVIATION...
Updated 1800Z.

Upper level trough digs SE into the northern Rockies and MT today
and tonight with flow aloft veering from W to NW. Surface cold front
crosses the Canadian border this afternoon and south through central
and SW MT tonight. VFR conditions initially will gradually
deteriorate with bands of snow showers developing this afternoon.
Front will move south through N-central MT terminals late this
afternoon and early evening bringing a wind shift to the north and
period of IFR/LIFR in snow with lighter snow and IFR in low clouds
continuing into Thursday morning. A period of north winds with gusts
20-30kts is likely to follow the frontal passage across the north-
central MT plains this evening as high pressure surges south behind
the front. Frontal passage will bring a wind shift and period of IFR
conditions to SW MT terminals overnight with snow continuing into
Thursday morning. Hoenisch

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF   3  11   9  34 /  90  50   0  20
CTB  -1  11   7  32 /  80  30   0  20
HLN  11  17  10  33 /  70  40   0  30
BZN  12  17   5  29 /  80  60   0  40
WEY  12  20  -1  22 /  90  40  10  50
DLN  15  23   9  30 /  50  20   0  30
HVR   2   6  -4  26 / 100  50   0  20
LWT   3  13   3  30 /  90  70   0  20

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 11 AM MST Thursday Broadwater...
Gallatin...Jefferson...Madison.

Winter Weather Advisory until 11 AM MST Thursday Blaine...
Chouteau...Eastern Glacier...Eastern Pondera...Hill...Liberty...
Toole.

Winter Weather Advisory until 11 AM MST Thursday Cascade...
Fergus...Judith Basin...Meagher.

Winter Weather Advisory until 11 AM MST Thursday Central and
Southern Lewis and Clark...Eastern Teton...Southern Rocky
Mountain Front.

Winter Weather Advisory until 11 AM MST Thursday Northern Rocky
Mountain Front.

Flood Warning for an ice jam until further notice central Broadwater
County near Townsend on the Missouri River.

&&

http://www.weather.gov/greatfalls

WWUS85 KTFX 000000
SPSTFX

Special Weather Statement
National Weather Service Great Falls MT
305 PM MST WED FEB 14 2018

MTZ012>014-047>051-150000-
Chouteau-Cascade-Southern Rocky Mountain Front-Fergus-Eastern
Teton-Blaine-Central and Southern Lewis and Clark-Judith Basin-
305 PM MST WED FEB 14 2018

...A SNOW SQUALL WILL IMPACT LEWIS AND CLARK...NORTHWESTERN
MEAGHER...JUDITH BASIN...FERGUS...SOUTHERN TETON...SOUTHWESTERN
BLAINE...SOUTHERN CHOUTEAU AND CASCADE COUNTIES...

At 301 PM MST, a snow squall stretched from Fairfield to Lewistown
and is moving southeast at 15 mph. This band of snow will produce a
quick reduction in visibility to a half a mile or less and will
produce a quick inch or two of snow over a short amount of time.
This band of snow will lead to rapidly changing road conditions over
a short amount of time.

Locations impacted include...
Great Falls, Lewistown, Cascade, Stanford, Lincoln, Fairfield, Belt,
Geraldine, Denton, Hobson, Winifred, Moore, Highwood, Black Eagle,
Geyser, Fort Shaw, Roy, Fort  Shaw, Augusta and Wolf Creek.

A winter weather advisory is in effect for the area. Please monitor
local media outlets and the national weather service for further
statements.

Conditions can deteriorate rapidly in winter weather situations. Be
prepared for snow or ice covered roads. Slow down and allow extra
time when traveling.

LAT...LON 4687 11076 4698 11092 4701 11108 4709 11109
      4709 11116 4701 11117 4700 11153 4692 11154
      4691 11165 4686 11164 4684 11280 4717 11279
      4718 11294 4772 11296 4773 10896 4687 10892
TIME...MOT...LOC 2201Z 329DEG 15KT 4737 11125

MARTIN

Special Weather Statement
National Weather Service Great Falls MT
321 PM MST WED FEB 14 2018

MTZ012>014-047>051-142345-
Chouteau-Cascade-Southern Rocky Mountain Front-Fergus-Eastern
Teton-Blaine-Central and Southern Lewis and Clark-Judith Basin-
321 PM MST WED FEB 14 2018

...A SNOW SQUALL WILL IMPACT LEWIS AND CLARK...NORTHWESTERN
MEAGHER...JUDITH BASIN...FERGUS...SOUTHERN TETON...SOUTHWESTERN
BLAINE...SOUTHERN CHOUTEAU AND CASCADE COUNTIES...

At 319 PM MST, a snow squall stretched from Fairfield to Lewistown
and is moving southeast at 15 mph. This band of snow will produce a
quick reduction in visibility to a half a mile or less and will
produce a quick inch or two of snow over a short amount of time.
This band of snow will lead to rapidly changing road conditions over
a short amount of time.

Locations impacted include...
Great Falls, Lewistown, Cascade, Stanford, Lincoln, Fairfield, Belt,
Geraldine, Denton, Hobson, Winifred, Moore, Highwood, Black Eagle,
Geyser, Fort Shaw, Roy, Fort  Shaw, Augusta and Wolf Creek.

A winter weather advisory is in effect for the area. Please monitor
local media outlets and the national weather service for further
statements.

Conditions can deteriorate rapidly in winter weather situations. Be
prepared for snow or ice covered roads. Slow down and allow extra
time when traveling.

LAT...LON 4687 11075 4698 11092 4701 11108 4709 11109
      4709 11116 4701 11117 4700 11153 4692 11154
      4691 11165 4689 11161 4686 11165 4683 11280
      4717 11279 4718 11293 4772 11296 4774 10895
      4687 10891
TIME...MOT...LOC 2219Z 329DEG 14KT 4739 11127

MARTIN