High Wind in Wyoming, November 12 to 13, 2021

Area Forecast Discussion
National Weather Service Cheyenne WY
801 PM MST Fri Nov 12 2021

.UPDATE...
Issued at 741 PM MST Fri Nov 12 2021

Forecast for tonight looks good with a High Wind Warning remaining
in effect for the northern Snowy Range Foothills, mainly along the
Interstate 80 corridor. Wind gusts at Arlington have increased
this evening with gusts of 60 MPH observed recently. Expect these
winds to get stronger and more widespread across the wind prone
areas of southeast Wyoming towards sunrise on Saturday. Elsewhere,
gusty winds should keep temperatures in the 30s to near 40
overnight along and west of the Nebraska/Wyoming border.

&&

.SHORT TERM...(Tonight - Saturday Night)
Issued at 213 PM MST Fri Nov 12 2021

High winds continue to be the primary forecast concern across much
of southeast Wyoming over the next several days. Low-lvl gradients
appear to be at a relative minimum w/ both the 700 & 850 mb CAG to
CPR gradient hovering around 45 meters this afternoon. Nonetheless
winds remain very strong near Arlington, sustained around 35 to 40
MPH with occasional gusts to 60 MPH. Low-level gradients will only
increase into the evening & overnight, as pressure falls gradually
spread across eastern Montana and Wyoming into the western Dakotas
by early Saturday. As such, no real break from the strong winds at
Arlington so the High Wind Warning has been extended yet again for
that zone until 8 PM MST Saturday. The start time of the High Wind
Watch was bumped up to start immediately afterwards as 700 mb CAG-
CPR gradients remain around 55 meters and a mountain-top inversion
gradually develops overnight. At their peak, gradients on Saturday
will be the strongest of this prolonged event at around 70 meters,
so it is quite possible to see a few more 70+ MPH wind gusts later
tonight and especially early Saturday as x-sections show potential
for substantial mountain wave activity off the Snowys. Expect flow
aloft to increase considerably over the central & southern Laramie
Range after 06z with the MSLP gradient increasing to 3-5 hpa along
the spine of the Laramie Range. Surface trough still appears to be
a bit close to I-25 to be confident in high winds at Bordeaux, but
it definitely looks better than previous days especially w/ better
subsidence and steeper low-level lapse rates. In-house probability
guidance shows a good chance (60% to 80%) of achieving 60 MPH wind
gusts at Bordeaux around 15z Saturday. Have added Bordeaux as well
as the I-80 Summit & Foothills to a High Wind Warning, starting at
1 AM MST tonight.

A good pattern for winds to spill out of the wind corridors during
the afternoon on Saturday as a strong clipper system sweeps across
the Dakotas, placing much of the CWA in the right exit region of a
140-160 knot 250 mb jet streak. Strong low-level CAA, coupled with
intense subsidence and a ribbon of 55 to 65 kt 700-800 mb flow and
unidirectional wind profiles strongly suggests potential for 60 to
70 MPH wind gusts at Cheyenne, Laramie, and possibly Wheatland too
during the late morning and afternoon hours. A High Wind Watch has
been hoisted for these adjacent zones between 8 AM and 8 PM MST on
Saturday. Some isolated to widely scattered rain/snow showers will
be possible w/ the cold front especially across our northern zones
on Saturday, but meager moisture profiles should keep things light
and insignificant.

.LONG TERM...(Sunday - Friday)
Issued at 213 PM MST Fri Nov 12 2021

The primary concern in the long term still remains the threat of
high winds in the wind prone areas. High Wind Watches have been
issued for the central and south Laramie Range, the south Laramie
Range foothills, the north Snowy Range foothills, and southwest
Platte County. These watches are in effect Sunday morning through
Monday afternoon. If guidance continues to hold on to these strong
winds, and tight gradients and strong subsidence persist, it is very
likely that these watches will be upgraded to warnings. Elevated to
high winds are still expected Monday night through Tuesday night due
to these strong gradients and subsidence.

Aside from wind, nothing too extraordinary to report in the extended
forecast. Sunday night, a ridge starts to build in for the start of
the work week. The ridge will help move out any lingering clouds
from the weekend's shortwave trough, so Monday should be mostly
sunny across the CWA. 700 MB temperatures are fairly mild so highs
on Monday are expected to be above average for this time of year.
Most places across the CWA will see temperatures anywhere from 10 to
almost 20 degrees above average! On Tuesday, some increased cloud
cover ahead of an approaching cold front will keep temperatures
about 10 degrees cooler than they were on Monday.

Tuesday night, a cold front drops in from the northwest bringing
with it some cold Canadian air and a chance of precipitation. Models
still have not come to an agreement about precipitation duration as
well as coverage. However, it is likely that the mountains will see
some snow during this time. There is also high confidence at this
time that temperatures will be much colder after the passage of the
cold front. High temperatures on Wednesday look to be at least 10
degrees colder than average; a stark difference from the mild
temperatures expected on Monday.

Thursday looks to be fairly quiet weather-wise. Temperatures look to
rebound back to roughly average for this time of year as we enter a
brief near-zonal flow pattern.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 409 PM MST Fri Nov 12 2021

VFR conditions expected to persist through the TAF period. Winds
at KCYS, KLAR have weakened, but may come back up with gusts 20 to
25 knots after 5Z. Winds across the Nebraska panhandle have also
weakened and will likely stay light until near 16Z when gusts 35
to 35 knots are possible through the afternoon. Around midnight
there's also a chance for 45 to 50 knots of west to northwest LLWS
at KCYS, KLAR, KBFF, and KSNY, but it will likely only last
until 15Z. Some light rain showers are also possible at KCDR and
KAIA tomorrow afternoon, but they will likely be short-lived and
have minimal impacts.

&&

.FIRE WEATHER...
Issued at 311 AM MST Fri Nov 12 2021

Windy conditions continue across southeast Wyoming into the Nebraska
Panhandle through at least Monday before they ease. Area on the north
side of a cold front this morning...will move back to the east as a
warm front later today. Winds expected to turn westerly as the front
moves east. High pressure builds into southeast Wyoming this evening into
Saturday with mainly dry weather and warmer temperatures. Afternoon
humidity stays well above critical levels with good to excellent overnight
recoveries. Next cold front approaches from the north Saturday night
into Sunday. Westerly winds ahead of this front will turn northwesterly
and remain strong behind the front. Very little in the way of precipitation
is expected at least through Monday. Given the relatively high afternoon
humidity...critical fire weather conditions are not expected. But given
the strong winds...any fires that do develop could spread rapidly in dead

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Warning until 8 PM MST Saturday for WYZ110.

     High Wind Watch from Saturday evening through Monday afternoon
     for WYZ110.

     High Wind Warning from 1 AM to 8 PM MST Saturday for WYZ106-116-
     117.

     High Wind Watch from Sunday morning through Monday afternoon for
     WYZ106-116-117.

     High Wind Watch from Saturday morning through Saturday evening
     for WYZ107-115-118.

NE...None.
&&

UPDATE...TJT
SHORT TERM...CLH
LONG TERM...SF
AVIATION...LK
FIRE WEATHER...GCC

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHEYENNE WY
713 PM MST FRI NOV 12 2021

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

0700 PM     NON-TSTM WND GST 1 NNW ARLINGTON         41.60N 106.21W
11/12/2021  M58 MPH          CARBON             WY   MESONET

            WYDOT SENSOR AT ARLINGTON. SUSTAINED WINDS
            BETWEEN 40 TO 45 MPH.

&&

TT

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHEYENNE WY
729 PM MST FRI NOV 12 2021

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

0716 PM     NON-TSTM WND GST 1 NNW ARLINGTON         41.60N 106.21W
11/12/2021  M60 MPH          CARBON             WY   MESONET

            WYDOT SENSOR AT ARLINGTON. SUSTAINED WINDS
            OF 42 TO 45 MPH.

&&

TT