High Wind in Montana, January 2 to 3, 2021

Area Forecast Discussion
National Weather Service Great Falls MT
157 PM MST Sat Jan 2 2021

.SYNOPSIS...

Strong and possibly damaging west to southwest winds develop
tonight along the Rocky Mountain Front, then expand across much
of North-central Montana Sunday. Areas of snow are likely over
the northern Rockies and the West Yellowstone area over the
weekend. Temperatures remain mild elsewhere, with mainly dry
conditions.

&&

.DISCUSSION...

Skies have mostly cleared over much of North-central and
Southwest Montana this afternoon, with some lower clouds lingering
over mountain areas. This is a brief break in the cloud cover, as
the next Pacific storm system approaches from the west.

The most significant weather concern through tomorrow is the onset
of strong, and potentially damaging winds across much of North
Central Montana. The surface pressure gradient has maintained
strong wind today along the Rocky Mountain Front. Mid level, and
hence surface winds are expected to increase this evening as a
compact short-wave trough drops through southern Alberta, and
shortwave ridging develops over Southwest Montana. The result for
us is a squeeze play, causing a period of much higher wind speeds.
The strongest winds will be confined to the tight pressure
gradient zone along the Rocky Mountain Front this evening. But
then as the lee side trough ejects eastward Sunday and couples
with the passing upper level trough, the wind field will expand
across North-Central Montana. High wind warnings remain in effect,
with the period of most widespread high winds expected mid morning
through early afternoon Sunday.

Pacific moisture embedded within the westerly flow will lift over
the Northern Rockies, providing a period of accumulating snow
mainly impacting travel over Marias Pass. Snow accumulation will
increase overnight through early Sunday as snow levels drop behind
the passing wave. A winter weather advisory remains in effect for
this area due to the potential for snow covered roads and blowing
snow.

Winds and snowfall decrease in coverage rather quickly Sunday
evening as the upper level trough moves away to the east. Ridging
follows on Monday for a fair, but slightly cooler weather day.

The next wave in the parade of Pacific weather systems arrives
Monday night. Forecast models indicate this wave is on a more
southerly track, and is likely to generate some welcome snowfall
for Southwest Montana Monday night through Tuesday. A period of
stronger winds appears likely for central Montana on Tuesday. This
is a rather unusual alignment for higher winds, and forecast
values here were pushed above NBM guidance.

Fair weather follows on Wednesday as another shortwave ridge
crosses the region. The operational guidance and ensemble members
begin to diverge Wednesday night, but overall maintain the mild
and periodically windy pattern through the end of the week.

&&

.AVIATION..
1050 AM MST Sat Jan 2 2021 (02/18Z TAF period)

VFR conditions prevail at area terminals, with higher clouds moving
away to the east, and lower stratus capping most mountain areas. The
main focus will remain on the increasing winds tonight through
Sunday across the plains of Central and North Central Montana, where
wind gusts in excess of 45 to 55 kts are likely. Low level wind
shear and mountain wave turbulence will become more widespread as
mid-level winds also strengthen.

Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  38  49  29  48 /   0   0   0   0
CTB  33  42  26  43 /  10  20   0   0
HLN  30  47  25  45 /   0  20   0  10
BZN  23  45  21  45 /   0  20   0   0
WYS  14  30  18  32 /  60  80  30  40
DLN  23  41  20  40 /   0  20   0  10
HVR  36  49  26  45 /   0  10   0   0
LWT  30  45  24  47 /   0  10   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Warning from midnight tonight to 5 PM MST Sunday
Cascade...Central and Southern Lewis and Clark...Chouteau...
Eastern Pondera...Eastern Teton...Liberty...Toole.

High Wind Warning from 8 AM to 7 PM MST Sunday Blaine...Fergus...
Hill...Judith Basin...Meagher.

Winter Weather Advisory until 5 PM MST Sunday Northern Rocky
Mountain Front.

High Wind Warning until 5 PM MST Sunday Eastern Glacier...
Northern Rocky Mountain Front...Southern Rocky Mountain Front.

&&

http://www.weather.gov/greatfalls

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
1232 PM MST SAT JAN 2 2021

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

0721 AM     NON-TSTM WND GST 8 SE EAST GLACIER PARK  48.36N 113.11W
01/02/2021  M79 MPH          GLACIER            MT   MESONET

            MESONET STATION DCRM8 DEEP CREEK RAWS.

&&

MOLDAN

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
1233 PM MST SAT JAN 2 2021

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

1207 PM     NON-TSTM WND GST 2 SSE GEYSER            47.25N 110.48W
01/02/2021  M58 MPH          JUDITH BASIN       MT   MESONET

            MESONET STATION MTGYS GEYSER (MT DOT).

&&

MOLDAN