An intense Pacific low pressure system produced heavy snowfall and strong winds up to 50 mph across east central, south central and southeast Wyoming. The strong winds caused blizzard conditions over western Carbon County in south central Wyoming.
Every event with a place to put it; 28 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.
An intense Pacific low pressure system produced heavy snowfall and strong winds up to 50 mph across east central, south central and southeast Wyoming. The strong winds caused blizzard conditions over western Carbon County in south central Wyoming. A narrow swath of 20 to 25 inches of snow fell from Wheatland to Torrington in southeast Wyoming. Elsewhere, snow accumulations ranged from 3 to 10 inches, with 10 to 20 inches over the mountains. This storm resulted in major impacts to transportation, resulting in numerous road and interstate highway closures.
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 Feb 21, 10:11 PM MST, 6 hours 49 minutes earlier.
Area Forecast Discussion
National Weather Service Cheyenne WY
1011 PM MST Tue Feb 21 2017
.UPDATE...
Issued at 758 PM MST Tue Feb 21 2017
We are within 12 hours of the start of snow in the Snowy and
Sierra Madre Ranges. So went ahead and upgraded to a warning.
Latest mosaic radar showing a band of fairly strong showers just
approaching eastern Sweetwater County now and should be into the
mountains of Carbon County in the next several hours. Updates have
been sent.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 343 PM MST Tue Feb 21 2017
Winds easing over the area this afternoon as the gradient likewise
is slackening. Expect a fairly quiet night across the CWA with
some increase in cloudiness mainly out west. Snow showers will
persist over the higher mtns as moisture rides up the west-facing
slopes.
One more mild day across the CWA Weds ahead of an upper trough
that will be over the western CONUS. Sctd rain and snow showers
will continue over far western parts of the CWA during the day as
the moisture feed continues over that area. Should see a slow
increase in clouds elsewhere. Meanwhile a lee cyclone will begin
developing over eastern Colorado by late in the day. More
significant changes should ensue Weds night as the lee cyclone
continues to deepen over eastern Colorado and colder air sinks
south across the CWA. Some diffluent upper flow and jet dynamics
should allow for an increasing area of snow with some banding
expected. Main problem will be the location of the heavier bands.
Models continue trend of shifting heavier activity a little
northward. Given trends in models have advanced the Winter Storm
Watch over the higher mtns to early Weds morning then started a WS
Watch over most of the rest of the CWA Weds night.
.LONG TERM...(Thursday through Tuesday)
Issued at 343 PM MST Tue Feb 21 2017
Significant winter storm is still on track for late Wednesday night
through Thursday night, taking aim at the CWA. The biggest change
in the 12Z guidance compared to previous cycles was a northward
shift in the axis of heaviest QPF, away from areas along the
Colorado Border, and toward the northern half of the CWA. Large
scale ascent (QG convergence) really gets going between 03-06Z
Thurs. There will likely be some banding also as the GFS indicates
good midlvl frontogenesis and elevated instability. Went ahead and
issued a Winter Storm Watch for almost the entire CWA with
widespread 6-12 inches over lower elevations. Was least confident
about amounts in areas along Interstate 80 due to the aforementioned
northward shift in the best forcing. Patchy blowing snow will be
possible through the event, especially by Thursday aftn/evening as
the pressure gradient strengthens and north winds gust to 30-35 mph.
Snow will begin to decrease in intensity by late Thursday evening
and into the night. The remainder of the extended will feature
below normal temps in northwesterly flow aloft, however it will be
mostly dry after Friday morning.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 950 PM MST Tue Feb 21 2017
Area of snow west of Laramie Range will impact both KRWL and KLAR
during the overnight hours. Expect IFR/LIFR conditions to remain
ongoing at KRWL through sunrise with timing at KLAR around 09Z.
HRRR is about 2 hours too slow on the onset, so adjusted
accordingly based off trends. A widespread snow event looking
likely across southeast Wyoming and nebraska Panhandle Wednesday
night through Friday morning that will have major impacts on all
airports across the area.
&&
.FIRE WEATHER...
Issued at 343 PM MST Tue Feb 21 2017
Fire weather concens will be quite low with a return to colder and
wetter conditions over the next few days.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Storm Watch from Wednesday evening through Friday morning
for WYZ101>110-113-115>119.
Winter Storm Warning from 5 AM Wednesday to 11 AM MST Friday for
WYZ112-114.
NE...Winter Storm Watch from Wednesday evening through Friday morning
for NEZ002-003-019>021-095-096.
Winter Storm Watch from Thursday morning through Friday morning
for NEZ054-055.
&&
UPDATE...GCC
SHORT TERM...RE
LONG TERM...ZF
AVIATION...GCC
FIRE WEATHER...REHazardous Weather Outlook National Weather Service Cheyenne WY 421 AM MST Wed Feb 22 2017 NEZ002-003-019>021-054-055-095-096-WYZ101-102-107-108-117>119- 231130- Dawes-Box Butte-Scotts Bluff-Banner-Morrill-Kimball-Cheyenne- North Sioux-South Sioux-Converse County Lower Elevations- Niobrara County-East Platte County-Goshen County- South Laramie Range Foothills-Central Laramie County- East Laramie County- 421 AM MST Wed Feb 22 2017 This hazardous weather outlook is for western Nebraska and for southeast Wyoming along and east of Interstate 25. .DAY ONE...TODAY AND TONIGHT Widespread accumulating snow will begin tonight and continue through early Friday. A Winter Storm Watch is in effect for the eastern plains of southeast Wyoming and western Nebraska for significant snow accumulations beginning after midnight tonight. Please refer to the Winter Storm Watch for additional details. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY Widespread accumulating snow will continue Thursday and possibly into early Friday. East to northeast winds will increase between 15 to 25 MPH with higher gusts on Thursday resulting in drifting snow but also some patchy blowing snow at times. The heaviest snow accumulations should be north of Interstate 80. .Spotter information statement... Spotters are urged to report snow accumulations Thursday and Friday. WYZ103>106-109>116-231130- North Laramie Range-Ferris/Seminoe/Shirley Mountains- Shirley Basin-Central Laramie Range and Southwest Platte County- Central Carbon County-North Snowy Range Foothills- Southwest Carbon County-Sierra Madre Range- Upper North Platte River Basin-Snowy Range-Laramie Valley- South Laramie Range- 421 AM MST Wed Feb 22 2017 This hazardous weather outlook is for portions of south central Wyoming and southeast Wyoming. .DAY ONE...TODAY AND TONIGHT Widespread accumulating snow will redevelop this afternoon with periods of snow continuing through the night outside the mountains. A Winter Storm Watch is in effect for all of Carbon and Albany county across southeast Wyoming for significant snow accumulations beginning this afternoon and this evening. Please refer to the Winter Storm Watch for additional details. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY Widespread accumulating snow will continue Thursday and possibly into early Friday. Wind direction will be variable Thursday and Thursday night since the low pressure system will be over the area...but will gust between 20 to 30 MPH at times resulting in drifting snow but also some patchy blowing snow at times. .Spotter information statement... Spotters are urged to report snow accumulations Thursday and Friday.
The national radar mosaic for the moment the first event began.
25 winter storm, 3 blizzard. Local standard time, as filed.
The Battle Mountain SNOTEL site (elevation 7440 ft) estimated 13.5 inches of snow.
The Old Battle SNOTEL site (elevation 10000 ft) estimated 16.5 inches of snow.
The Little Snake River SNOTEL site (elevation 8915 ft) estimated 18 inches of snow.
The Blackhall Mountain SNOTEL site (elevation 9820 ft) estimated 12 inches of snow.
The North French Creek SNOTEL site (elevation 10130 ft) estimated 12 inches of snow.
The Sand Lake SNOTEL site (elevation 10050 ft) estimated 16.5 inches of snow.
The Brooklyn Lake SNOTEL site (elevation 10240 ft) estimated 20 inches of snow.
The Cinnabar Park SNOTEL site (elevation 9574 ft) estimated 13.5 inches of snow.
The Medicine Bow SNOTEL site (elevation 10500 ft) estimated 20 inches of snow.
The Crow Creek SNOTEL site (elevation 8330 ft) estimated 13.5 inches of snow.
The Windy Peak SNOTEL site (elevation 7900 ft) estimated 18 inches of snow.
Six to fourteen inches inches of snow was observed. Muddy Gap received a foot of snow.
Six to twelve inches of snow was observed from Rawlins to Sinclair to Hanna.
Six to eight inches of snow was observed in and around Saratoga. Six to twelve inches fell at Encampment and Riverside.
Five to eight inches of snow was observed at Shirley Basin and Medicine Bow. Strong northwest winds produced two to three foot snow drifts.
Moderate to heavy snowfall and northwest winds gusting between 40 and 50 mph created near-blizzard conditions with visibilities as low as a quarter mile. Interstate 80 was closed between mile markers 240 and 290. Five to ten inches of snow was observed. Snow drifts of one to two feet were common.
Ten to twelve inches of snow was observed in and around Rock River.
Six to sixteen inches of snow was observed. Fifteen inches of snow was measured four miles west-southwest of Douglas. Eleven inches of snow was measured at Douglas.
Six to ten inches of snow was observed countywide.
Eight to twenty-two inches of snow was observed, heaviest over the central Laramie Range.
Eight to twenty-four inches of snow was observed, heaviest near Wheatland.
Ten to twenty-four inches of snow was measured countywide. La Grange received 20 inches, Fort Laramie 18 inches, and Torrington 24 inches. Snow drifts of two to four feet were observed.
Five to ten inches of snow was observed, with the heaviest at Horse Creek.
Six to thirteen inches of snow was observed, heaviest 25 miles north of Cheyenne.
Four to eight inches of snow was reported, heaviest at Gun Barrel and Albin.
The combination of northwest winds gusting to 50 mph and heavy snowfall produced blizzard conditions. Visibilities were reduced to less than a quarter mile for several hours along Interstate 80 from west of Rawlins to Walcott Junction. Interstate 80 was closed from east of Walcott Junction to the Carbon-Sweetwater county line. Two to four foot snow drifts were reported.
The combination of heavy snowfall and northwest winds gusting to 40 mph created blizzard conditions. Visibilities at Baggs and Dixon were less than a quarter mile for several hours.
The combination of heavy snowfall and northwest winds gusting to 45 mph created blizzard conditions. Visibilities were reduced to less than a quarter mile for several hours at Muddy Gap.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2017Every state in 2017This day in weather historyWarnings in Wyoming, February 2017
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: 687408, 687411, 687413, 687415, 687435, 687439, 687447, 687451, 687453, 687458, 687461, 687656, 687657, 687658, 687659, 687663, 687664, 687665, 687666, 687677, 687684, 687694, 687695, 687696, 687697, 687653, 687654, 687655.