High Wind in Montana, December 21, 2018

Area Forecast Discussion
National Weather Service Great Falls MT
300 AM MST Fri Dec 21 2018

.SYNOPSIS...

Valley rain and mountain snow spreads across western and southwest
Montana this morning. Icy and snow-covered roads will create
hazardous driving conditions in some areas, mainly along and west
of the Continental Divide. Strong winds will accompany this storm
system over areas along the east slopes of the Rockies and
portions of central Montana through this afternoon. Generally
fair weather follows for the weekend, with cooler temperatures.

&&

.DISCUSSION...

There are no changes to the previous thinking with regards to
the weather system moving across the region this morning, which will
bring strong to high winds to much of the Chinook Front and
primarily mountain snow. Snowfall amounts along the I-90 corridor
are generally less than an inch, but even a brief period of heavier
snowfall could produce hazardous travel with icy roads at a critical
time of day. The pre- to near-dawn timing of the snowfall, combined
with expected heavier traffic along the interstate Friday morning
prompts a Winter Weather Advisory for portions of Southwest Montana.
Impacts could be particularly troublesome over Homestake Pass and
from around Belgrade to Bozeman Pass. Further north, the combination
of high winds and periods of snow will cause difficult travel
conditions with reduced visibility over the summits of Marias Pass,
Rogers Pass, and MacDonald passes. These potential weather impacts
will develop quickly, but also clear up quickly as the system
departs Friday afternoon. Fair weather follows on Saturday as drier
air returns under a strengthening upper level ridge, though breezy
conditions will remain.

Saturday night through next Friday...The progressive pattern that we
have been in for the past week or so looks to continue through the
middle of next week. This ongoing pattern of shortwave troughs
followed by shortwave ridges will continue to shift the weather
regimes from wet and windy weather, to mild and dry weather on and
off through next week. An upper level trough over the forecast area
Saturday will track eastward through Saturday night, with some brief
ridging moving over the area during the overnight hours. By Sunday
morning, this ridge of high pressure will quickly decay as another
shortwave trough approaches from the west and brings another round
of precipitation and gusty winds along with it. As that system
dissipates over the area Sunday night, another series of waves will
track across the area Monday morning through Thursday. There remains
a good deal of uncertainty as to the strength, track, and timing of
these disturbances and their resulting impacts to specific areas.

&&

.AVIATION...
Updated 0552z.

No significant changes to the late evening Aviation discussion.

The approaching Pacific trough will increase winds aloft, likely
peaking from 12Z to 18Z. As a result there will be mountain wave
activity, turbulence, and low level wind shear for much of the TAF
period. Ceilings will begin to lower along the Rocky Mountain Front
and in southwest Montana around 6Z which will cause mountain
obscuration and MVFR conditions for these areas. A quick moving band
of snow is expected to move through the southwest terminals which
could briefly lower ceilings and visibility to IFR levels generally
in the 10 - 15Z time frame. Otherwise, snow will be confined to
areas immediately east of the leeside of the northern Rocky Mountain
Front. rcg

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  44  22  37  23 /  10   0   0   0
CTB  43  18  34  19 /  10   0   0   0
HLN  41  21  34  17 /  10   0   0   0
BZN  39  14  32  11 /  80   0   0   0
WEY  26   5  21   4 / 100  20  10   0
DLN  38  12  29  12 /  40   0   0   0
HVR  44  20  34  16 /  10  20   0   0
LWT  39  19  32  18 /  20   0   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until noon MST today Broadwater...
Gallatin...Jefferson...Madison.

High Wind Warning until 3 PM MST this afternoon Northern Rocky
Mountain Front...Southern Rocky Mountain Front.

High Wind Warning until 3 PM MST this afternoon Central and
Southern Lewis and Clark...Judith Basin.

Winter Weather Advisory until noon MST today above 4500 feet for
Northern Rocky Mountain Front.

Winter Weather Advisory until noon MST today Beaverhead.

High Wind Warning until 11 AM MST this morning Eastern Glacier.

&&

http://www.weather.gov/greatfalls

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
1151 PM MST THU DEC 20 2018

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

0909 PM     NON-TSTM WND GST 2 SE BROWNING           48.54N 112.98W
12/20/2018  M70 MPH          GLACIER            MT   MESONET

            MESONET STATION MTBWG, BROWNING MDT.

&&

FMK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
1213 AM MST FRI DEC 21 2018

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

1127 PM     NON-TSTM WND GST 4 NNE MCALLISTER        45.50N 111.70W
12/20/2018  M54 MPH          MADISON            MT   MESONET

            MESONET STATION MTNOR, NORRIS HILL MDT.

&&

FMK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
145 AM MST FRI DEC 21 2018

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

0100 AM     NON-TSTM WND GST 14 W BYNUM              47.98N 112.61W
12/21/2018  M55 MPH          TETON              MT   MESONET

            MESONET STATION DELMT, DELLWO - 13 W BYNUM.

&&

FMK