High Wind in Montana, December 9, 2018

Area Forecast Discussion
National Weather Service Great Falls MT
1140 AM MST Sun Dec 9 2018

Aviation Section Updated.

.UPDATE...
Very minor updates made to the forecast, mostly with regards to
refreshing temperatures within the first 6 hours based on current
observations and trends. Otherwise the forecast remains on track.
-TP

&&

.SYNOPSIS...

High pressure will keep the region dry through tonight, with mild
temperatures and breezy westerly winds over the plains, but near
normal temperatures in the southwest. A low pressure trough will
then bring increasing clouds to the area Monday into Monday
night with areas of light snow in the mountains. Gusty winds and
clearing skies will return for Tuesday. A series of disturbances
will then bring periods of precipitation and gusty winds to the
region through the end of the week.

&&

.AVIATION...
Updated 1740Z.

VFR conditions will continue across most of north central and
southwest Montana at least through Monday afternoon. High pressure
aloft will mainly allow only increasing high cloudiness over the
area. Gusty westerly winds will begin to ramp up monday morning
along the Rocky Mountain Front, and continue to increase through
Tuesday. -TP

&&

.PREV DISCUSSION...
/ISSUED 445 AM MST Sun Dec 9 2018/

Today through Tuesday...A high pressure ridge will move over
north central and southwest Montana through tonight, which will
keep the area dry with mainly increasing high cloudiness. However,
low and mid clouds will linger along and west of the Continental
Divide and in far southwest Montana in the Centennial Valley
adjacent to the Idaho border and into the West Yellowstone area. A
low pressure trough will then move into the Pacific Northwest on
Monday and into the Northern Rockies Monday night. The resulting
southwest flow aloft will spread mid level cloudiness over the
area with snow showers for the mountains along and west of the
Divide and into southwest Montana. Breezy westerly downslope
winds will increase through the period over the plains, which
should hinder precipitation development there. Precipitation will
generally decrease on Tuesday as the trough exits the area.
Slightly above normal temperatures across north central Montana
will cool back closer to normal on Tuesday with the passage of a
cold front, while temperatures remain below normal in the
southwest.  Coulston

Tuesday Night through Sunday...A more progressive weather pattern
develops for this period in the wake of Tuesday's trough. The
approach of the next low pressure trough will bring increasing
westerly mid level winds Tuesday afternoon through Tuesday night,
which should translate down to the surface over the plains,
especially near the Rocky Mountain Front, where gusts should
exceed 50 mph at times. High wind highlights are not anticipated
at this time, but the situation will continue to be monitored. The
passage of the trough and its associated Canadian cold front on
Wednesday will likely bring measurable snowfall to the mountains
across the area, along with a chance for precipitation over the
plains, as temperatures cool back closer to normal. The westerly
mid level wind flow will increase once again Thursday into Friday,
bringing gusty westerly downslope winds to the plains once again.
This time around, winds could become strong enough along the Rocky
Mountain Front (gusts potentially in excess of 70 mph) and
possibly over adjacent plains (gusts potentially in excess of 50
mph) to warrant high wind highlights. This westerly flow will
likely also bring persistent light precipitation to the mountains
of the Rocky Mountain Front. Another low pressure trough will
spread snow over area mountains Friday night into Saturday, with
precipitation possibly falling on some of the plains. Although
this trough appears weaker than the previous one, forecast models
indicate that most of the area could get below normal temperatures
on Saturday. Brief high pressure ridging will likely keep much of
the area dry Saturday night, but another system will likely bring
mountain precipitation again on Sunday.
Coulston

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  44  24  40  22 /   0   0   0   0
CTB  40  28  39  20 /   0   0   0   0
HLN  34  10  37  16 /   0   0   0  10
BZN  33   8  36  14 /   0   0  10  20
WEY  26  -1  30   2 /   0   0  10  40
DLN  33   8  33  11 /   0   0  10  40
HVR  39  19  41  20 /   0   0   0   0
LWT  42  22  42  22 /   0   0   0  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&

http://www.weather.gov/greatfalls