Winter Storm Warning 17, NWS Great Falls, MT

Area Forecast Discussion
National Weather Service Great Falls MT
1049 AM MST Thu Dec 19 2019

...AVIATION SECTION UPDATED...

.SYNOPSIS...

Windy conditions will prevail along the Rocky Mountian Front and
across the plains of north central Montana through Saturday. On
Friday, strong winds and blowing snow could cause near blizzard
conditions in the mountain of the Rocky Mountain Front. At lower
elevations, mostly dry conditions and above average temperatures
are expected through Saturday. Cooler temperatures are expected
next week with some showers possible, mainly over the mountains.

&&

.UPDATE...

The morning update has been published. Only minor adjustments
were made to the current forecast package. Friday's High Wind
Watch will likely be upgraded to warning with the afternoon
package for the Rocky Mountain Front and portions of North-central
Montana. Winter highlights will be considered for snow and winds
in the mountains along the Northern Rocky Mountain Front.

&&

.AVIATION...
Updated 1048 AM MST Thu Dec 19 2019 (18z/19 TAF period)

Westerly flow aloft will bring an increasing likelihood for snow
over the mountains of the Rocky Mountain Front with mountain
obscurations expected for the duration of the TAF period. Lower
elevations east of the Continental Divide will see breezy to windy
conditions along with variable mid and high level cloudiness. Strong
winds aloft are expected through the forecast period for a
continuing chance of low level wind shear and turbulence aloft.

&&

.PREV DISCUSSION...
/ISSUED 331 AM MST Thu Dec 19 2019/

Upper level shortwave trough currently over the region continues
moving eastward today, with an extremely moist westerly flow
setting up for tonight and Friday, and possibly even into the
weekend. Abundant mountain snows are expected along the northern
Continental Divide, but strong downslope winds will keep the
plains and valleys mostly dry and relatively warm. Friday through
Saturday will see the westerly flow aloft become southwesterly as
troughing develops along the West Coast Increased lift ahead of
the trough will allow surface low pressure to develop in Alberta
while mountain top level winds increase to near 75 knots or more.
These winds will combine for another round of strong and gusty
winds for the Rocky Mountain Front and the adjacent plains of
north central Montana early Friday morning through late Friday
night. Snow and blowing snow will likely affect travel through
Marias Pass and portions of Glacier National Park. A High Wind
Watch remains in effect for western portions of north central
Montana for this wind and blowing snow event.

Medium range forecast model ensembles remain unchanged in that
they are continuing to suggest that the trough along the West
Coast will develop into a cutoff low off Baja and Southern
California early next week. Montana remains well north of the
energy associated with this storm system so am not expecting any
additional heavy precipitation events through Christmas and Boxing
Day. However, the region can expect a slow cooling trend with
breezy west winds likely through much of next week. mpj

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  42  33  51  35 /   0   0   0   0
CTB  38  26  46  32 /  10  20  20  20
HLN  39  22  46  26 /   0   0   0   0
BZN  37  18  43  21 /   0   0   0   0
WEY  25  14  30  13 /  20  20  30  10
DLN  31  18  37  22 /  10  10   0   0
HVR  35  25  46  31 /   0   0   0   0
LWT  40  28  46  34 /   0   0   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Watch from late tonight through Friday evening
Cascade...Eastern Pondera...Eastern Teton...Judith Basin...Toole.

High Wind Watch from late tonight through Friday evening Eastern
Glacier...Northern Rocky Mountain Front...Southern Rocky
Mountain Front.

&&

http://www.weather.gov/greatfalls