A slow moving area of low pressure moved out of Great Basin and passed very slowly across the southern portion of Wyoming and brought heavy snow to much of the southern two thirds of the state. The heaviest snow in the mountains fell over the East Slopes of the Wind River Mountains where favorable upslope flow brought over 2 feet of new snow to many areas with a maximum of 34 inches at the…
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The episode as NWS RIW wrote it up.
A slow moving area of low pressure moved out of Great Basin and passed very slowly across the southern portion of Wyoming and brought heavy snow to much of the southern two thirds of the state. The heaviest snow in the mountains fell over the East Slopes of the Wind River Mountains where favorable upslope flow brought over 2 feet of new snow to many areas with a maximum of 34 inches at the Townsend Creek SNOTEL. In the lower elevations, the heaviest snow fell across Sweetwater County. In Rock Springs and Green River, over a foot of snow was common with as much as 23 inches in some locations. The Lander Foothills and Wind River Basin where also hard hit with 12 to 18 inches of snow common. In addition, strong mid level winds mixed to the surface in some areas and brought blizzard conditions to portions of central and southern Wyoming. Portions of Interstate 80 as well as Highway 28 over South Pass were closed at times during the height of the storm.
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 Riverton, WY wrote its last area forecast discussion before the first event at Feb 22, 4:37 PM MST, 3 hours 23 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 437 PM MST Wed Feb 22 2017 .SHORT TERM...Today through Saturday The shortwave now nosing into Eastern Nevada is the weather feature that will deliver anticipated major winter storm to much of central and Southern Wyoming east of the Divide, as well as over Sweetwater County during the next couple of days. This open wave will close off over the Idaho/utah border by 12z Thursday and then quickly propagate east of the Divide and set up shop over Sweetwater and Carbon County in Southern wyoming east of the Divide by 18z Thursday. This storm will be quite the potent snow maker. To start with, a large swath of isentropic lift will stream northward across Sweetwater and Natrona Counties and wrap around the low to the north and west Thursday morning. A distinct mid level circulation will quickly develop over Northeast Sweetwater County by 09z Thursday late tonight and then just wobble around slowly for about 15 hours with very slow eastward movement through 00z Friday. As this powerful storm becomes organized, the low will actually become vertically stacked during the morning Thursday. As far as the outcome of this storm system goes, the NAM which originally kept all the energy way to our south over Colorado, is now bringing all the weather elements too far west with a dry slot moving into Casper Thursday. Will side with the ECMWF and the GFS. Both models are advertising large snow amounts with similar dynamics. One of the main differences is that the GFS negatively tilts the trough which is a favorable shape for a strong winter time storm complex. The advantage to the Euro is that it elongates the trough east west which would favor continued pieces of vorticity and subsequent bands of snowfall parading west even through Friday long after the main low exits to the southeast. Each of the two models spit out quite a bit of QPF with some areas in the vcnty of Casper as well as some other areas seeing as much as 2 inches of precip or so. The heaviest snowfall will likely occur from 8 am Thursday through 5 pm Thursday when strong QG forcing, frontogenesis, and the development of the deformation axis all come together, not to mention heavy snowfall in areas with close proximity to the mid level low. The surface low will become tightly wrapped with many areas of the CWA responding to this with ne winds of 20 to 30 mph along with gusts of 40 to 50 mph, and even 60 mph in areas like Sweetwater County, Southeast Fremont County, as well South pass where we went ahead and hoisted a blizzard warning for these areas (Eastern Sweetwater County, the Wind River Mtns to accommodate South Pass, and the Green and Granite Mountains including Jeffrey City) with the strongest winds and winter storm warnings for a large swath from western Sweetwater County, across Fremont County, the Owl Creek Mtns and into the Johnson and Natrona Counties. The warning areas could pick up as much as 2 feet of snow on Casper Mountain from late tonight through Friday along with 18 inches or so in the city of Casper, along with 10 to 16 inches fairly common in the warned areas which includes Riverton and Lander and points south and east. For the fringe zones, we issued advisories for the Cody Foothills, and the Big Horn Mtns. Decided to extend the warning through 18z Friday during which time light to occasional moderate snowfall would continue for the aforementioned reasons related to the trough extending out to the west, and keeping in mind that there will be a lot of anticipated travel during this time frame. Even though Northern Johnson County will not see more than 3 to 5 inches of snow, the strong north winds of 20 to 30 mph with gusts to 50 should justify the warning there. This will be one for the books. While this is all going on, the far west will continue to have periods of light snow or flurries with relatively light snow accumulations with the asct upper level trough nearby. Even the Upper Green river basin will respond to the storm with strong north winds and lighter amounts of snow. Temperatures will be colder behind this weather system with highs in the teens and 20s and lows from -5 to 10 above. Saturday will be relatively benign except for continued light snow in the west from moist westerly flow as high pressure builds in from the west. .LONG TERM...Saturday Night Through Wednesday Southeast moving shortwave Saturday night will bring at least some higher terrain/mtn snow showers with possibly a little bit across the lower elevations for a couple hours with trough passage. Brief ridging Sunday but with upglide developing out west for light snow developing. Inversions in the central basins with deep snow cover will keep it quite chilly...20s if we're lucky maybe teens in Fremont and parts of Natrona where the wind doesn't blow. Turning unsettled again Sunday night through Tuesday with snow out west and a chance of snow developing east of the divide. Models vary on trough location, timing and strength but it looks like we'll at least get a period of snow across the south and far north in addition to significant snow potential out west. Cold nw flow on Wednesday with enough moisture for snow in the far west, especially nw. Windy se half or so on Monday before cold front moves s/se across the area. Overall a pretty cold end to February with h7 temps staying generally between -12c and -18c. && .AVIATION.../00Z ISSUANCE/ WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES Snow and IFR conds will develop across the I80 corridor and KRKS as a major snowstorm takes shape later tonight through at least Thursday night or Friday morning. Otherwise, isolated to scattered snow showers in the western mountains through the period. EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES VFR conditions will prevail through 02Z at the terminal sites. MVFR conditions will develop in Northern WY after 00Z as ceilings lower and scattered light snow occurs. In central WY, snow will develop around 06Z Thursday with MVFR/IFR conditions occurring. A major snowstorm will impact most of the area later tonight through Friday morning with snow, strong wind and generally IFR conds. && .FIRE WEATHER... A significant winter storm will bring areas of moderate to heavy snow to much of the area east of the Divide later tonight and continue into the day Friday. Gusty northerly winds will occur with this snow Thursday. Light to moderate snow will also occur west of the Divide, ending from south to north Friday evening. && .RIW WATCHES/WARNINGS/ADVISORIES... Blizzard Warning until 11 AM MST Friday for WYZ030. Blizzard Warning from 11 PM this evening to 11 AM MST Friday for WYZ014-015-019. Winter Storm Warning from 11 PM this evening to 11 AM MST Friday for WYZ007-017-018-020-022. Winter Storm Warning from 5 AM Thursday to 11 AM MST Friday for WYZ010-011. Winter Weather Advisory from 5 AM Thursday to 11 AM MST Friday for WYZ003-005-009. Winter Storm Warning until 11 AM MST Friday for WYZ028-029. && SHORT TERM...Lipson LONG TERM...Skrbac AVIATION...Skrbac FIRE WEATHER...Lipson
Hazardous Weather Outlook National Weather Service Riverton WY 149 PM MST Wed Feb 22 2017 WYZ001>020-022>030-231200- Yellowstone National Park-Absaroka Mountains-Cody Foothills- North Big Horn Basin-Southwest Big Horn Basin- Southeast Big Horn Basin-Owl Creek and Bridger Mountains- Bighorn Mountains West-Bighorn Mountains Southeast- Northeast Johnson County-Southeast Johnson County- Teton and Gros Ventre Mountains-Jackson Hole- Wind River Mountains West-Wind River Mountains East- Upper Wind River Basin-Wind River Basin-Lander Foothills- Green Mountains and Rattlesnake Range- Natrona County Lower Elevations-Casper Mountain-Star Valley- Salt River and Wyoming Ranges-Upper Green River Basin Foothills- Upper Green River Basin-South Lincoln County- Rock Springs and Green River-Flaming Gorge-East Sweetwater County- 149 PM MST Wed Feb 22 2017 ...Flood Warning remains in effect for the Big Horn River roughly between Manderson and Greybull into Thursday... ...Blizzard Warnings for South Pass...Green Mountains and Rattlesnake Range area and Eastern Sweetwater County including Interstate 80 developing tonight and continuing into Friday morning... ...Winter Storm Warnings across much of the central and southern Wyoming late tonight through Friday morning... ...Winter Weather Advisories for the Big Horn Mountains...Cody Foothills and Hot Springs County Thursday through Friday morning... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight Ice jam flooding continues across portions of the Big Horn Basin especially along the Big Horn River in Big Horn County. A significant winter storm will develop tonight over southern portions, bringing moderate to heavy snow across eastern, central and southern portions of the forecast area. Please see the highlights for further details. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday Thursday and Friday...Significant snow will fall during the day Thursday across Johnson, Natrona, Fremont and Sweetwater counties, before subsiding by mid day Friday. The heaviest snow is expected across Natrona...Fremont and Eastern Sweetwater Counties. Gusty north to northeast winds will develop Thursday morning, from Buffalo to Casper to South Pass to Rock Springs, causing areas of blowing and drifting snow and blizzard conditions in some areas. Winds will gradually subside Thursday night. Light to moderate snow will also return across the far western mountains. Sunday night through Monday night...Significant snow possible across western valleys and mountains. .SPOTTER INFORMATION STATEMENT... Spotters are encouraged to report any river or creek flooding, as well as snowfall amounts. Thank you! Team Riverton
Special Weather Statement National Weather Service Riverton WY 750 PM MST Wed Feb 22 2017 WYZ027-231500- South Lincoln County- Including the cities of Kemmerer and Cokeville 750 PM MST Wed Feb 22 2017 ...Snow developing tonight and fall through the day Thursday... Areas of snow over northern Utah will move over southern Lincoln County tonight. Periods of moderate snow will be possible tonight, as a developing low pressure system moves across southern WY. 1 to 3 inches are expected by sunrise Thursday, with an additional 1 to 2 inches possible through the day. Gusty west to northwest winds of 15 to 25 mph with gusts up to 30 mph will also develop Thursday morning, causing blowing and drifting snow during the morning commute. This could make travel difficult, creating slick roads and reducing visibilities.
The national radar mosaic for the moment the first event began.
11 winter storm, 4 blizzard. Local standard time, as filed.
A CocoRaHS observer measured 10 inches of snow at the Buckboard Marina.
Very heavy snow fell through Rock Springs and Green River. Amounts over a foot were common. The highest amount recorded was 23 inches in Rock Springs. Interstate 80 was shut down for a time due to the snow and drifting snow from gusty winds.
A trained spotter measured 8 inches of snow in Wamsutter. Southeast of Rock Springs, 11 inches of snow was measured.
Very heavy snow fell across the East Slopes of the Wind River Range with amounts over two feet commonplace. Some of the highest amounts reported for SNOTELs included 34 inches at Townsend Creek and 28 inches at Deer Park. A COOP observer reported 26 inches of new snow at Atlantic City.
The SNOTEL on Casper Mountain reported 17 inches of new snow.
Heavy snow fell across portions of Natrona County. The heaviest snow fell in the western portions of Natrona County where Powder River picked up 13 inches of new snow. Amounts around the city of Casper generally ranged from 4 to 8 inches with 9.4 at the Natrona County airport. Much less snow fell in northern Natrona County where only 1 inch of snow fell at Midwest.
Heavy snow fell across the Green and Rattlesnake Range. The highest snow amount measured was 17 inches at Jeffrey City.
Trained spotters measured 6 to 9 inches around Farson. Snowfall amounts decreased further north in the zone.
At the Lander airport, 16 inches of snow fell. Snowfall amounts around the Lander foothills generally ranged from 9 to 18 inches.
Heavy snow fell through portions of the Wind River Basin. At the Riverton airport, 13 inches of snow was measured with 9 to 12 inches through the city of Riverton. Further north, downsloping flow off of the Owl Creek Mountains kept accumulations lower. At Boyson Dam, there was 6 inches of snow.
A long period of blizzard conditions occurred over South Pass with frequent wind gusts past 40 mph and heavy snow combined to bring white out conditions over Wyoming 28. The road was closed through this period.
A long period of blizzard conditions occurred over South Pass with frequent wind gusts past 40 mph and heavy snow combined to bring white out conditions over Wyoming 28. The road was closed through this period.
The weather sensor at Beaver Rim along Highway 28 reported visibility below a quarter of a mile and frequent wind gusts over 35 mph for several hours on the morning of February 23rd.
A CocoRaHS observer measured 7 inches of snow 4 miles southwest of Buffalo.
The Rock Springs airport had visibility drop to around a quarter of a mile and frequent wind gusts past 35 mph on February 23rd. These conditions led to nearly impossible travel conditions and closure of Interstate 80 for several hours.
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: 679893, 679894, 679896, 679904, 679899, 679898, 679903, 679905, 679812, 679813, 679901, 679902, 679900, 679897, 679895.