High Wind in Montana, November 10 to 13, 2021

Area Forecast Discussion
National Weather Service Great Falls MT
412 AM MST Wed Nov 10 2021

...Aviation Section Updated...

.SYNOPSIS...
Generally cooler conditions are expected today with gusty westerly
winds behind a cold frontal passage early this morning. After a
few cooler days on Wednesday and Thursday, expect warmer
temperatures over the weekend, with a chance for a passing rain or
snow shower.

&&

.DISCUSSION...

Today through Thursday...

Cold front has crossed north-central and southwest Montana this
morning with only residual snow falling across the mountains and
western and northwestern slopes. Was tempted to go ahead and
cancel the Winter Weather Advisory but will let it be until
expiration at 5 AM this morning. Gusty west to northwest winds
developed as expected behind the front overnight, and these gusty
winds will continue through a good part of the day today before
laying down with the loss of daytime heating this evening. Highs
today for much of the region will be about ten degrees cooler than
Tuesday given persistent cold advection through the period.
Cyclonic flow aloft transitions to anti-cyclonic flow Wednesday night
under fair skies and light winds, allowing temperatures to drop
well down into the teens to mid-20s. A disturbance crosses the
region from northwest to southeast Thursday into Thursday night,
with enough moisture and instability for snow shower activity
primarily confined to the mountains. Highs Thursday will be nearly
uniform across the region in the lower to mid-40s at lower
elevations, with cold advection on the plains keeping temperatures
cooler than Wednesday while southwest MT temperatures warm several
degrees under increased cloud cover and warm advection.

Friday through next Wednesday...

Fast westerly flow will mean a rapid-fire series of warm and cold
fronts cross the region with a persistently active jet stream.
Given the jet stream remains nearly overhead, breezy and mild
conditions with above normal temperatures with brief periods of
precipitation should be expected. In these type of patterns, the
details especially with any precipitation can be really tough to
nail down more than a couple of days in advance.

Global model ensembles have all been hinting at a period of below
normal temperatures and an increased chance of snow at some point
between the November 15th and November 20th, but latest trends
suggest the core of the cold, and better snow chances, will be
shunted north and east of our region. However, this will bear
close watching as only a minor deviation in the jet stream south
could mean colder and snowier conditions with much greater impacts
than currently anticipated.

&&

.AVIATION...
412 AM MST Wed Nov 10 2021 (10/12Z TAF period)

Low-level wind shear exists this morning at several terminals after
cold frontal passage overnight has resulted in a turbulent and windy
low-level atmosphere, but those winds are not quite mixing all the
way to the surface. By late morning or early afternoon, if not
sooner, those winds will mix down and result in windy conditions
across much of the region. Winds subside late this afternoon through
early evening with the loss of daytime heating/mixing. VFR
conditions will predominate, except for a brief period of MVFR for
the next couple of hours at KWYS.

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  44  21  41  25 /  10   0   0  10
CTB  41  20  39  22 /   0   0   0  10
HLN  44  25  42  29 /   0   0  20  10
BZN  42  20  40  25 /  10  10  30  10
WYS  32  15  34  23 /  10  20  40  20
DLN  39  20  43  28 /   0  10  20  10
HVR  47  20  41  17 /  10   0   0   0
LWT  42  21  38  20 /  10   0   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 5 AM MST early this morning
Beaverhead...Gallatin...Madison.

&&

http://www.weather.gov/greatfalls