A slow moving area of low pressure brought heavy snow to portions of central Wyoming. Impacts during the daylight hours were minimal in the lower elevations, since the strong April sun angle kept roads mainly wet.
Every event with a place to put it; 5 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 RIW wrote it up.
A slow moving area of low pressure brought heavy snow to portions of central Wyoming. Impacts during the daylight hours were minimal in the lower elevations, since the strong April sun angle kept roads mainly wet. As temperatures dropped when the sun set, roads became slick and many were closed at night. The highest amounts were in Riverton, Wyoming, where up to a foot of snow fell. Elsewhere, Lander, Wyoming had up to 9 inches with 8 inches at Thermopolis, Wyoming.
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 Apr 14, 4:01 AM MST, 59 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 501 AM MDT Wed Apr 14 2021 .SHORT TERM...(Today through Thursday) Issued at 450 AM MDT Wed Apr 14 2021 The first round of snow in the south and southwest has occurred with light accumulations per webcams. This area of snow will continue to push north this morning with some light snow in the central zones and into northwest WY. A a dry slot is evident in Sweetwater county at 430 AM, and this will bring a lull in the snow today. The north zones will be mostly dry today. High temperatures today will be in the 30s with some lower 40s in the far south, far west, and the Big Horn Basin. Mountain highs will be in the 20s. Windy in the south today with that northeast wind continuing with gusts 35 to 50 mph. The second round of snow will move from southwest to northeast across the region tonight into Thursday morning. Models continue to peg parts of central WY with heavy snow, including the Wind River Basin, Lander, and the east slopes of the Wind River mountains. Have upgraded the winter storm watches to advisories and warnings. The northwest and northern Big Horn basin will see the least amount of snow from this weather system. The most hazardous impacts to roads will be after sunset tonight through late Thursday morning. Snow will be decreasing in intensity by late Thursday morning through the afternoon over the region. Lows tonight will be in the 20s with teens in the mountains. Highs on Thursday will be in the 30s east of the divide with a few lower 40s in the Big Horn Basin. Highs in the 30s and 40s will occur west of the divide. Mountains highs will be in the 20s for the most part. .LONG TERM...(Thursday night through Wednesday) Issued at 450 AM MDT Wed Apr 14 2021 At the beginning of the long-term, the system impacting the area in the short-term looks to be continuing. Most of the heavier precipitation looks to be over by this point, however. Heaviest amounts from 00Z Friday into 00Z Saturday look to be over the mountain ranges with the Bighorns possible seeing as much as another 6 inches. Outside of the mountains, expect accumulations to be less than 2 additional inches with many places seeing well under an inch. Temperatures still look to be quite cold with highs remaining in the 30s in many locations. The Wind River and Bighorn Basins may have the biggest jump and reach well into the 40s, but if there is any snow on the ground then highs may need to be adjusted downwards on later shifts. Saturday and most of Sunday look to be fairly benign as an east-west oriented ridge impacts the area. It is still possible that there may be a bit of lingering moisture on Saturday, but any accumulations look to be very light and confined to the higher elevations. By 00Z Monday, the next cold front from the north may start impacting western areas. This feature is expected to quickly dive southward during the day Monday with more moisture activity. It looks like Monday could be quite windy with a strong northerly flow. H7 temperatures look to drop quite a bit on Monday behind the front so any precipitation that starts as rain looks to change to snow that does come through may be in the form of snow as the cold air filters in behind the front. Confidence is low for Tuesday and Wednesday, but more precipitation is possible for both days. && .AVIATION...(For the 12Z TAFS through 12Z Thursday) Issued at 450 AM MDT Wed Apr 14 2021 Waves of snow showers are expected across central and southern areas through 00Z Thursday with significant lulls possible. A more persistent snowfall is expected especially across central areas Wednesday night. Also the northern terminals (KCOD and KWRL) will then have better chances of snow. MVFR or low VFR ceilings are expected through the TAF period, but a trend to lower ceilings are expected after 00Z Thursday. KCPR, KLND, KRIW will likely have a prolonged period of IFR visibilities in snow Wednesday night with the worst conditions at KLND. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts. && .FIRE WEATHER... Issued AT 450 AM MDT Wed Apr 14 2021 Periods of snow today and tonight over most of the fire zones. The heaviest snow will occur in the central and parts of the southwest through Thursday. The north zones will see the least amount of snow. Windy over most of the region today through Thursday. Conditions will be improving for Friday with snow showers in the mountains and isolated snow showers at the lower elevations. && .RIW WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until noon MDT Thursday for WYZ027>030. Winter Storm Warning from 3 PM this afternoon to midnight MDT Thursday night for WYZ019. Winter Storm Warning until 6 PM MDT Thursday for WYZ015-018-024. Winter Weather Advisory from midnight tonight to 6 AM MDT Friday for WYZ010-011. Winter Storm Warning from 6 PM this evening to noon MDT Thursday for WYZ016-017. Winter Weather Advisory from 6 PM this evening to 6 PM MDT Thursday for WYZ020-022. Winter Weather Advisory from midnight tonight to noon MDT Friday for WYZ008-009. Winter Weather Advisory from 9 PM this evening to noon MDT Thursday for WYZ005. Winter Weather Advisory from 6 PM this evening to 6 AM MDT Friday for WYZ007. && SHORT TERM...AR LONG TERM...Clayton AVIATION...Murrell FIRE WEATHER...AR
Hazardous Weather Outlook National Weather Service Riverton WY 300 AM MDT Wed Apr 14 2021 WYZ001>020-022>030-151100- 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- 300 AM MDT Wed Apr 14 2021 ...Winter Storm Warnings and Winter Weather Advisories are posted for parts of Central and Southwest Wyoming Today through Thursday... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight. Periods of snow today over the central and south. A chance of snow in the west. Heavier snow will occur tonight in central Wyoming. Please see winter weather statements for more details. Windy over the south today and tonight with increasing wind speeds in the central tonight. Expect hazardous driving conditions later this evening through the late night hours as roadways become snow packed or icy. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday. Thursday...Periods of snow along and east of the divide. A chance of light snow in the west. Friday...A chance of snow showers. Monday...A chance of snow along and east of the continental divide. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report significant weather conditions, according to standard operating procedures.
Special Weather Statement National Weather Service Riverton WY 550 AM MDT Wed Apr 14 2021 WYZ026-150000- Upper Green River Basin- Including the cities of La Barge, Big Piney, and Farson 550 AM MDT Wed Apr 14 2021 ...Periods of snow Today and Tonight... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...Periods of light snow today with light accumulations. Another round of snow will occur tonight with snowfall of 1 to 3 inches expected. * WHERE...Upper Green River Basin. * WHEN...Today and Tonight. * ADDITIONAL DETAILS...Area roads may be slick late this evening through Thursday morning. Highway 28 from near South Pass to Farson will have a northeast wind of 25 to 35 mph with gusts around 45 mph today and tonight. Visibility will be reduced in snow and blowing snow. WYZ003-150000- Cody Foothills- Including the cities of Clark, Cody, and Meeteetse 550 AM MDT Wed Apr 14 2021 ...Snow Tonight into Thursday morning... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...Periods of light snow today with light accumulations. Another round of snow will occur tonight with snowfall of 1 to 3 inches expected. Locally higher amounts may occur around Meeteetse. * WHERE...Cody Foothills. * WHEN...Tonight into Thursday morning. * ADDITIONAL DETAILS...Area roads may be slick late this evening through Thursday morning. Highway 120 will be impacted. WYZ014-150000- Wind River Mountains West- 550 AM MDT Wed Apr 14 2021 ...Periods of snow Today and Tonight... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...Snow and wind expected. Snowfall of 2 to 6 inches. Northeast wind of 25 to 35 mph with gusts around 45 mph. This includes Atlantic City and South Pass City. * WHERE...West Wind River Mountains. * WHEN...Today and Tonight. * ADDITIONAL DETAILS...Highway 28 over South Pass may be very difficult to impossible tonight due to snow and blowing snow. WYZ002-150000- Absaroka Mountains- 550 AM MDT Wed Apr 14 2021 ...Periods of snow Today and Tonight... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...Mainly light snow Today. Then a period of moderate to heavy Tonight. Snowfall of 2 to 6 inches, with the most occurring on the east slopes of the range. * WHERE...Absaroka mountains. * WHEN...Today and Tonight. * ADDITIONAL DETAILS...Use caution if traveling in this area. Roads leading into the mountains will be slick and snow covered at times with low visibility.
The national radar mosaic for the moment the first event began.
5 winter storm. Local standard time, as filed.
A combination of heavy snow and high wind lead to the closure of US 28 over South Pass.
Snowfall amounts around Lander, Wyoming generally ranged from 6 to 12 inches.
A combination of heavy snow and gusty wind brought hazardous travel conditions that lead to the closure of US 287.
Snowfall amounts around Riverton, Wyoming ranged from 6 to 12 inches. At the National Weather Service office, 7.7 inches of snow fell. The snow caused slick roads around the area and lead to closure of several school districts.
Snowfall amounts around Thermopolis, Wyoming ranged from 6 to 8 inches.
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, April 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: 953769, 953770, 953771, 953772, 953773.