High sustained winds occurred late in the morning on the 17th near the Arlington gap area along Interstate 80 which resulted in Interstate 80 between Laramie and Rawlins being closed to light, high-profile vehicles for an extended period of time.
Every event with a place to put it; 1 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS CYS wrote it up.
High sustained winds occurred late in the morning on the 17th near the Arlington gap area along Interstate 80 which resulted in Interstate 80 between Laramie and Rawlins being closed to light, high-profile vehicles for an extended period of time.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Cheyenne, WY wrote its last area forecast discussion before the first event at Dec 17, 5:27 AM MST, 4 hours 45 minutes earlier.
Area Forecast Discussion
National Weather Service Cheyenne WY
527 AM MST Fri Dec 17 2021
.SHORT TERM...(Today - Sunday)
Issued at 413 AM MST Fri Dec 17 2021
Periods of light snow are likely to persist through this afternoon
for the Snowy & Sierra Madre mountain ranges as a strong mid-level
short wave sweeps eastward across the central Rockies. Orographics
should become less favorable with time, suggesting that additional
accumulations should be light. SNOTEL SWE observations based on 15
or 20 to 1 ratios suggest that 6-12 inches of snow have fallen for
the Sierra Madres w/ possibly up to 18 inches at Old Battle (10000
feet) in the last 24 hours. Lesser amounts for the Snowy Range, as
was expected but nonetheless still in the 4-8 inch range. A Winter
Weather Advisory will remain valid until 15z this morning. No need
to upgrade to Warnings as the locally extreme totals are basically
at mountain top and the heaviest snow has concluded.
H7/H85 CAG to CPR gradients have climbed to near 50-60 meters over
the last several hours. However, flow aloft remains modest only at
45 knots or so over the southeast Wyoming wind corridors. Not much
subsidence in place either as the trough axis has yet to push east
across the CWA. Peak wind gusts through the night have been in the
45-50 MPH range at both Arlington & Bordeaux, and do not expect to
see them get much stronger unless subsidence improves, and that is
unlikely to occur until afternoon when gradients diminish. A small
window of opportunity could exist for a few stronger gusts nearing
60 MPH in the next few hours as the parameter space is expected to
be the best around 15z per in-house guidance. This is the case for
both ARL and BRX, but a limited 2-3 millibar MSLP gradient from W-
E along the spine of the Laramie Range leads to a scenario w/ very
low confidence. Nonetheless, will keep inherited High Wind Warning
going through 18z today as a few rogue gusts are not impossible.
A few snow showers will be possible through the early afternoon as
weak dynamic lift overspreads the region, but fully expect to have
winds increasing during the afternoon as the upper disturbance and
associated front push to the east. Day shift will need to pay very
close attention to winds from the I-80 summit eastward into CYS as
GFS soundings suggest very steep lapse rates and hint at excellent
subsidence nudging into the I-25 corridor. Modest H7 flow at 45 kt
or so will be limiting factor for gusts higher than 50 MPH, but we
could see a brief gust to 60 MPH or two even here in Cheyenne. The
ARL area should see an increasing threat for high winds by 3z this
evening as H85 CAG-CPR gradients begin a gradual climb to near 65-
70 meters by 12z Saturday. Subsidence will be much stronger in the
wake of the short wave, so despite very modest low-level flow over
the region, gusts up to 60 MPH appear likely to develop. Have gone
ahead and issued a new High Wind Warning for Arlington starting at
9 PM MST tonight.
Low-level gradients continue to increase on Saturday and even into
early Sunday morning with a peak H85 CAG-CPR gradient expect to be
around 80 meters at 12z Sunday per the GFS. High winds will likely
persist at Arlington through this entire period, so have initially
extended the warning through 00z Monday, but in all honesty it may
require further extensions down the road. Bordeaux will get in the
action as well as the ARL-BRX MSLP gradient is progged to increase
significantly by 12z Saturday, peaking around 5-7 mbs by later Sat
night or early Sun morning which is quite good for that gap. Local
probabilistic guidance strongly suggests potential for a few gusts
exceeding 60 MPH on Saturday w/ the best chance for stronger gusts
after 06z Sunday as gradients strengthen further. Expect potential
for gusts around 65-75 MPH for both Arlington & Bordeaux early Sun
morning. Winds are unlikely to die down for either zone by the end
of the forecast period.
.LONG TERM...(Sunday Night - Thursday)
Issued at 413 AM MST Fri Dec 17 2021
Fair amount of uncertainty in the long term forecast with models
having a difficult time locking onto a solution, and significant
differences in the last 24 to 48 hours. At this time, mostly dry
conditions, outside of some mountain snow possible, and gusty to
strong winds, with an upper level ridge pushing eastward from the
west coast. Long range models have begun shifting from a deep
ridging pattern engulfing much of the western and central CONUS to
more of a split flow regime with a mid to upper level closed low
developing across northern Texas, and near zonal flow across the CWA
through early Tuesday morning. High winds will remain an issue
Monday and Tuesday, with continued shortwave disturbances within the
flow pulsing eastward across the CWA. Monday's wind do appear to be
confined to the wind prone areas, with the NBM v4.1 Probability of
Exceeding 48kts indicate a high likelihood of stronger winds along
near the Central Laramie Range and eastward into Bordeaux and the
CAG-CPR gradients jumping from 60 to 70 meters before 18Z. By late
Tuesday, near zonal flow will begin transitioning towards a ridging
pattern as the upper level closed low pushes further eastward across
the Deep South. Stronger winds should begin moving further eastward
on Tuesday, with the better subsidence in the omega fields, steep
lapse rates, and mountain top inversions indicating mountain wave
signatures. Will need to monitor Tuesday for any high wind headlines
needed, especially for Platte, Laramie, and Kimball Counties. Next
chance for precipitation is progged for Thursday into Friday. Models
have been a bit aggressive with POPs those two days, with greater
than 60 in the higher elevations. Even with some moisture advection
into the region and orographic snow possible, upper level ridging
appears to remain firmly in place, and 60+ POPs seem difficult to
justify. Went ahead and started trending POPs downward, along with
the other surrounding WFOs.
&&
.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 359 AM MST Fri Dec 17 2021
VFR to MVFR conditions likely through the forecast period for all
terminals. Gusty winds expected to continue for the next 24 hours
and even into the weekend. Ceilings are expected to lower through
the afternoon, and cannot fully rule out MVFR conditions at KLAR,
KRWL, KCDR, and KAIA.
&&
.FIRE WEATHER...
Issued at 413 AM MST Fri Dec 17 2021
No fire weather concerns. Periods of windy conditions will persist
over the next few days, but cooler temperatures and resulting high
RH values will limit potential for rapid fire spread.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory until 8 AM MST this morning for WYZ112-
114.
High Wind Warning until 11 AM MST this morning for WYZ106-110.
High Wind Warning from 9 PM this evening to 5 PM MST Sunday for
WYZ110.
High Wind Warning from 5 AM Saturday to 5 PM MST Sunday for
WYZ106.
NE...None.
&&
SHORT TERM...CLH
LONG TERM...MD
AVIATION...MD
FIRE WEATHER...CLHThe national radar mosaic for the moment the first event began.
1 high wind. Local standard time, as filed.
WYDOT mesonet station Arlington (KARL) along Interstate 80 measured average sustained winds of 40 MPH for over an hour. Maximum wind gust during this period was 57 MPH.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2021Every state in 2021This day in weather historyWarnings in Wyoming, December 2021
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 990033.