High Wind in Montana, November 20 to 22, 2021

Area Forecast Discussion
National Weather Service Great Falls MT
123 PM MST Sat Nov 20 2021

.SYNOPSIS...

Breezy and dry conditions are expected through the remainder of
the weekend and into the start of the upcoming work week, with
high temperatures on Monday climbing into the 50s to low 60s.

&&

.DISCUSSION...

Rest of today through Monday...primary forecast concerns throughout
the period will be winds and elevated fire weather concerns.

Predominately northwesterly flow is expected across the Northern
Rockies through 12z Monday as H500 ridging over the eastern Pacific
slowly builds east to over the Pacific Northwest/Western Canada
through Sunday. A potent H500 shortwave over the Gulf of Alaska
(Sunday evening) is then expected to slide/dig east to over the
Pacific coasts of Canada/the Pacific Northwest by Monday afternoon,
which will result in the ridge over the Northern Rockies flattening
out and the flow becoming nearly zonal. Strong, but for the most
part remaining below high wind criteria, winds are expected
through much of the period across the plains of Central/North
Central Montana and north-south orientated valleys of Southwest
Montana. It is not entirely out of the question that a few
isolated locations approach or hit high wind criteria Sunday
afternoon through Monday afternoon (i.e. Eastern Glacier, Rocky
Mountain Front, Montana Hwy 200 corridor between Great Falls and
Geyser, and Norris Hill), but given the lack of widespread and
continuous gusts exceeding high wind criteria I will forgo any
highlights for now. Of more concern will be increasing fire
weather concerns for the day on Monday as highs climb into the
upper 50s to low 60s over the plains of Central and North Central
Montana. Given the abnormally dry conditions across the region
this fall, combined with the forecasted above normal temperatures,
strong winds, and minimum relative humidity values falling into
the teens on Monday, elevated to locally near- critical fire
weather conditions are expected. Will message these fire weather
concerns to partners directly for now; however, fire weather
highlights may be needed. - Moldan

Tuesday through Saturday... The upper-level ridge responsible for
above average temperatures Monday will quickly exit eastward
Tuesday, ahead of an approaching upper trough. The upper trough will
move onshore over the Pacific Northwest early Tuesday, eventually
passing overhead Tuesday night/Wednesday morning. High
temperatures will cool by approximately 10 degrees both Tuesday
and Wednesday, which would put the region at just about average
for this time of the year on Wednesday. Precipitation associated
with the trough is expected to be confined primarily to the
Continental Divide and areas favorable for orographically forced
precipitation in a west to southwest wind across Southwest and
Central Montana, but a few areas of precipitation may make it onto
the plains Tuesday afternoon. After Wednesday, a brief ridge
builds overhead for Thanksgiving, before flattening out towards
next weekend. Shortwaves traversing through zonal flow may allow
for precipitation primarily along the Continental Divide and in
Southwest Montana late next week, but I do not have enough
confidence to pinpoint any day over another that is more favorable
for precipitation. For that reason, I have opted to stick with
the National Blend of Models late next week. -AM

&&

.AVIATION...
955 AM MST Sat Nov 20 2021 (20/12Z TAF period)

VFR conditions are expected throughout the duration of the 2018/2118
TAF period; however, lower CIGS to near 5000ft AGL may linger prior
to 21z near the KBZN and KEKS before eroding/lifting. Otherwise the
main impact to terminal operations throughout the period will be
increasing southwest to west winds, mainly over the plains of
Central and North Central Montana. Wind gusts this afternoon and
early evening of 25-40kts can be expected here, with brief periods
of higher gusts. Mountain obscuration will decrease through the day,
with the one exception of the Continental Divide. Some mountain wave
turbulence can't be ruled out in lee of the Rocky Mountain Front
throughout the period. - Moldan

KWYS TAF will not be issued until airport operations resume next
spring.

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  25  50  40  60 /   0  10   0   0
CTB  21  44  31  54 /   0  10   0   0
HLN  24  50  29  55 /   0  10   0   0
BZN  21  46  24  52 /   0   0   0   0
WYS  16  31  14  39 /   0   0   0   0
DLN  21  44  25  49 /   0   0   0   0
HVR  18  43  28  57 /   0   0   0   0
LWT  22  46  31  61 /   0   0   0   0

&&

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

http://www.weather.gov/greatfalls

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
1129 AM MST SAT NOV 20 2021

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

1006 AM     NON-TSTM WND GST 1 ENE EAST GLACIER PARK 48.45N 113.20W
11/20/2021  M55 MPH          GLACIER            MT   MESONET

            MESONET STATION MTBRN TWO MEDICINE BRIDGE
            (MT DOT).

&&

BRUSDA

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
1131 AM MST SAT NOV 20 2021

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

1121 AM     NON-TSTM WND GST 8 SE EAST GLACIER PARK  48.36N 113.11W
11/20/2021  M73 MPH          GLACIER            MT   MESONET

            MESONET STATION DCRM8 DEEP CREEK RAWS.

&&

BRUSDA

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
1225 PM MST SAT NOV 20 2021

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

1132 AM     NON-TSTM WND GST 3 SW CUT BANK           48.60N 112.37W
11/20/2021  M56 MPH          GLACIER            MT   ASOS

            ASOS STATION KCTB CUT BANK AIRPORT.

&&

BRUSDA