Snow Squall Warning 2, NWS Great Falls, MT

Area Forecast Discussion
National Weather Service Great Falls MT
303 PM MST Thu Jan 2 2020

.SYNOPSIS...

Expect above normal temperatures to continue for Friday and
Saturday. A cold front will move through the area on Saturday
afternoon, producing strong winds over North Central MT and a
chance for snow showers over the Rockies and Southwest MT.

&&

.DISCUSSION...

Rest of this afternoon through Saturday night...primary forecast
concerns throughout the period is accumulating mountain snow
(through Friday afternoon) and very strong winds (beginning Friday
night along the Rocky Mountain Front and Saturday morning over the
remainder of the plains of Central/North Central Montana).

A surface cold front has pushed south across North Central and into
Central Montana as of this afternoon. This cold front has brought a
sharp wind shift to the north, along with periods of moderate to
heavy snow to the plains of North Central Montana. As the remainder
of the afternoon progresses, I expect the cold front to stall along
the Central Montana mountains due to the rising terrain and
weakening pressure rises behind the front. This cold front is then
expected to retreat north during the overnight hours and into Friday
morning as a warm front, which will bring warming temperatures for
Southwest through North Central Montana. Mountain snow is expected
to continue during the overnight hours along the Continental Divide
and across the Central Montana mountains (i.e. Big and Little Belt,
Castle, Crazy, and Snowy), with snowfall accumulations of 2-5"
expected. While mountain passes like Marias, Deep Creek, and Kings
Hill will see this accumulating snow; will refrain from issuing any
Winter Weather Advisories for now as a majority of the snow will be
falling during the overnight hours. None-the-less, snow covered
roads and periods of reduced visibilities are expected, and motorist
are urged to exercise caution.

Focus then turns to a very strong shortwave, which will quickly
slide east from over the Pacific Northwest Friday night and across
the Northern Rockies through Saturday evening. This shortwave will
not only bring accumulating mountain snow to the Continental Divide
(generally above 5000ft), but also very strong winds to the Rocky
Mountain Front and plains of Central/North Central Montana. With
snow accumulations of 6-12" possible above 5000ft along the Northern
and Southern Rocky Mountain Fronts, Winter Weather highlights may
be needed due to impacts to travel for areas like Marias Pass. As
previously just stated, very strong surface winds are also expected
with this shortwave from Friday afternoon through Saturday evening.
Winds will first become strong Friday afternoon along the Northern
and Southern Rocky Mountain Fronts as a lee side surface trough
sharpens and cross barrier flow strengthens. Increasing stability at
or slightly above ridgetops Friday night, combined with the
strengthening cross barrier flow, will likely lead to mountain wave
activity along the Rocky Mountain Front. As the shortwave
approaches the region Saturday morning and cold air is advected in
across the region, expect ridgetop stability to decrease. While this
decrease in stability will likely decrease the threat for mountain
wave activity, steepening lapse rates and subsidence behind the
wave will allow for ideal mixing over the plains of Central/North
Central Montana. With H850-700 flow of 50-80kts and mixing expected
through these layers on Saturday, confidence continues to grow in
the idea that widespread wind gusts of 60-80 mph will be possible
over the plains of Central/North Central Montana. Have elected to
upgrade the High Wind Watch for the Northern/Southern Rocky Mountain
Front and Eastern Glacier County to a High Wind Warning with this
forecast package as confidence in High Wind criteria wind
speeds/gusts is very high. With the onset of these winds expected to
hold off until later Saturday morning over the plains of
Central/North Central Montana, will hold onto the High Wind Watch
for now, but upgrades to at least portions of the area will likely
be needed. - Moldan

Sunday through Thursday...Afternoon temperatures will cool a bit
starting Sunday after the passage of the cold front on Saturday,
however, expect temperatures to still generally average about 4
to 8 degrees above normal in many areas. The chances for
precipitation will be low to start the week, but gradually
increase towards the middle portion of the week. Also, winds are
expected to increase once again, mostly from Tuesday into
Wednesday over North Central MT. A high wind highlight might be
needed for portions of North Central MT. Brusda

&&

.AVIATION...
Updated 1000 AM MST Thu Jan 2 2020 (02/18Z TAF Period)

Moist and unstable northwest flow aloft will promote scattered snow
showers through the afternoon hours for most terminals across
Southwest, Central, and North Central Montana. While VFR conditions
are generally expected with these snow showers, MVFR/near-IFR
condtions can't be ruled out. Periods of mountain obscuration is
likely today and through the overnight hours. Winds will also be
breezy at most terminals through the afternoon hours, with
decreasing winds this evening. - Moldan

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  26  48  41  46 /  20  20  10   0
CTB  21  43  32  43 /  10  10  10  10
HLN  29  44  30  42 /  30  20   0  20
BZN  22  41  22  42 /  40  40   0  50
WYS  12  26  10  29 /  60  60  10  70
DLN  21  37  22  37 /  10  10   0  40
HVR  19  42  34  47 /  10  10  10  10
LWT  21  43  36  46 /  40  30  10   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Watch from Saturday morning through Saturday evening
Cascade...Central and Southern Lewis and Clark...Eastern
Pondera...Eastern Teton...Toole.

High Wind Warning from noon Friday to 9 PM MST Saturday Northern
Rocky Mountain Front...Southern Rocky Mountain Front.

High Wind Watch from Saturday morning through Saturday evening
Blaine...Chouteau...Fergus...Hill...Judith Basin...Liberty.

High Wind Warning from 3 AM to 9 PM MST Saturday Eastern Glacier.

&&

http://www.weather.gov/greatfalls

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
1031 AM MST THU JAN 2 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1030 AM     HEAVY SNOW       7 SE ROCKY BOY          48.18N 109.69W
01/02/2020  M12.0 INCH       HILL               MT   TRAINED SPOTTER

            CORRECTS PREVIOUS SNOW REPORT FROM 7 SE
            ROCKY BOY.

&&

MOLDAN

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
207 PM MST THU JAN 2 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0200 PM     SNOW             4 SSE HOGELAND          48.80N 108.61W
01/02/2020  E2.0 INCH        BLAINE             MT   TRAINED SPOTTER

            SNOW SQUALL PRODUCING 1 TO 2 INCHES OF HEAVY
            WET SNOW. VISIBILITY DOWN TO LESS THAN ONE
            QUARTER OF A MILE. WIND GUSTS ESTIMATED AT
            20 TO 30 MPH.

&&

MPJ

Special Weather Statement
National Weather Service Great Falls MT
212 PM MST Thu Jan 2 2020

MTZ047-022145-
Blaine-
212 PM MST Thu Jan 2 2020

...A DANGEROUS SNOW SQUALL WILL AFFECT NORTHERN BLAINE COUNTY...

At 211 PM MST, a dangerous snow squall was located 21 miles west of
Turner, or 25 miles northeast of Chinook or near Hogeland, moving
east at 20 mph.

Locations impacted include...
Turner and Hogeland.

Visibilities will drop quickly to near zero in this dangerous squall.

Use extra caution if you must travel into or through this dangerous
snow squall. Rapid changes in visibility and potentially slick roads
are likely to lead to accidents. Consider delaying travel until the
squall passes your location.

LAT...LON 4900 10823 4891 10826 4875 10826 4874 10832
      4858 10831 4856 10835 4844 10835 4844 10842
      4841 10841 4862 10884 4866 10930 4900 10935
TIME...MOT...LOC 2111Z 283DEG 17KT 4886 10887

JANGLIN

Special Weather Statement
National Weather Service Great Falls MT
221 PM MST Thu Jan 2 2020

MTZ012-013-050-051-054-022200-
Chouteau-Cascade-Fergus-Judith Basin-Meagher-
221 PM MST Thu Jan 2 2020

...A SNOW SQUALL WILL AFFECT NORTHEASTERN MEAGHER...JUDITH BASIN...
SOUTHWESTERN FERGUS...SOUTHWESTERN CHOUTEAU AND EASTERN CASCADE
COUNTIES...

At 220 PM MST, a snow squall was located 12 miles northeast of
Geyser, or 13 miles north of Stanford, moving east at 50 mph.

Locations impacted include...
Stanford, Belt, Denton, Hobson, Geyser, Highwood, Neihart,
Raynesford, Windham, Moccasin, Monarch, Sluice Boxes State Park,
Ackley Lake State Park, Sapphire Village, Stockett, Utica, Tracy,
Centerville, Coffee Creek and Armington.

This includes the following highways...
 Highway 200 between mile markers 0 and 65.
 Highway 89 between mile markers 16 and 71, and between mile markers
72 and 89.

Visibilities will drop quickly to less than a quarter of a mile in
this squall.

Use extra caution if you must travel into or through this dangerous
snow squall. Rapid changes in visibility and potentially slick roads
are likely to lead to accidents. Consider delaying travel until the
squall passes your location.

LAT...LON 4726 11108 4740 11127 4760 11109 4764 11070
      4754 11005 4741 10983 4714 10972 4689 10973
      4673 11081 4700 11109
TIME...MOT...LOC 2120Z 282DEG 42KT 4735 11025

JANGLIN

Special Weather Statement
National Weather Service Great Falls MT
257 PM MST Thu Jan 2 2020

MTZ012-013-050-051-054-022245-
Chouteau-Cascade-Fergus-Judith Basin-Meagher-
257 PM MST Thu Jan 2 2020

...A SNOW SQUALL WILL AFFECT NORTHEASTERN MEAGHER...JUDITH BASIN...
SOUTHWESTERN FERGUS...SOUTH CENTRAL CHOUTEAU AND SOUTHEASTERN CASCADE
COUNTIES...

At 256 PM MST, a snow squall was located near Stanford, moving
southeast at 45 mph.

Locations impacted include...
Stanford, Belt, Denton, Hobson, Moore, Geyser, Neihart, Raynesford,
Windham, Moccasin, Monarch, Sluice Boxes State Park, Ackley Lake
State Park, Sapphire Village, Stockett, Utica, Garneill, Danvers,
Coffee Creek and Armington.

This includes the following highways...
 Highway 200 between mile markers 0 and 76.
 Highway 89 between mile markers 10 and 71, and between mile markers
72 and 79.

Visibilities will drop quickly to less than a quarter of a mile in
this squall.

Use extra caution if you must travel into or through this dangerous
snow squall. Rapid changes in visibility and potentially slick roads
are likely to lead to accidents. Consider delaying travel until the
squall passes your location.

LAT...LON 4711 10948 4689 10971 4669 10967 4670 10982
      4675 10996 4675 11005 4671 11015 4672 11027
      4663 11028 4663 11039 4669 11088 4716 11127
      4733 11125 4749 11088 4752 11046 4720 10945
TIME...MOT...LOC 2156Z 301DEG 39KT 4722 11012

JANGLIN