A strong cold front moved across Wyoming and brought high wind to northern portions of the state. The highest wind was at the Johnson County airport in Buffalo, Wyoming, where the wind gusted as high as 70 mph.
Every event with a place to put it; 4 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 strong cold front moved across Wyoming and brought high wind to northern portions of the state. The highest wind was at the Johnson County airport in Buffalo, Wyoming, where the wind gusted as high as 70 mph. Other notable wind gusts included 62 mph north of Kaycee, Wyoming and 58 mph at the Powell, Wyoming Airport.
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 8, 3:36 PM MST, 16 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 436 PM MDT Thu Apr 8 2021 .SHORT TERM...Tonight through Saturday night Issued at 202 PM MDT Thu Apr 8 2021 Today the main concerns in the short term portion of the forecast are the bookends, mainly tonight and early tomorrow and Saturday night into Sunday, with few concerns in the middle. We will start with tonight. The main concern tonight will be a strong cold front that will sweep across the area through tomorrow morning. And with most cold fronts, we have two concerns, wind and snow. We will start with wind. We are already seeing gusty wind across the west and this will spread eastward through this afternoon and evening. The question is about the potential for high winds. There are few concerns for pre frontal wind, so we will focus on post frontal. The models continue to show a good pressure gradient across the area, although the 17 millibar gradient is less than the 21 from yesterday. Pressure rises are still impressive though, around 9 mb per 3 hours on average. These are factors for high wind. However, there are some things against it. One is that area will be on the wrong side of the jet, most areas in the left front quadrant which promotes upward motion. In addition, 700 millibar winds remain below the usual 50 knot threshold needed. So, we will stick with special weather statements for strong winds. We can't rule out an isolated high wind gust, but at this point this appears to be more of an exception rather than the rule. At this point, the strongest wind will be in the Jackson Valley, northern Johnson County as well as the Wind River Basin, with the longest duration in Johnson County. All areas will see winds decrease on Friday. Now for the second concern, snow. The aforementioned jet will help promote some upward motion as the front moves through. However, the front is a fast mover so most areas should only see a short period of snow. Things could get nasty for a time, since snow could be briefly heavy given the dynamics and gusty winds with the frontal passage. Again, we will stick with strongly worded special weather statements. The heaviest snow would likely occur this evening in the west and between midnight and 6 am east of the Divide. Snow should taper off fairly quickly after sunrise Friday with all snow over by noon. There should then be a period of around 36 to 48 hours of more tranquil weather as high pressure builds over the area. Most of Friday will be a dry but cooler day across the area. Saturday also looks like a dry day. The GFS tries to sneak some precipitation into the north late in the day. However, given the fast bias of the model we left things dry. This will be a warmer day though. And with the pressure gradient increasing ahead of another approaching cold front, gusty winds will develop in the areas favored by southwest flow. This is mainly from Rock Springs through southern Johnson County. With low humidity this could bring some elevated fire weather to some areas. This front will move southward across the area Saturday night into Sunday. There is more uncertainty with this system though. It almost certainly looks like a cooler and windier day. There is a lot of disagreement on the extent of any showers associated with it. This system does appear to have less moisture to work with though. So for now, we kept PoPs in the slight chance to chance range until there is more model consensus. .LONG TERM...Sunday through Thursday Issued at 202 PM MDT Thu Apr 8 2021 A strong cold front should be across the entire forecast area by 12Z Sunday. There could be lingering snow showers especially over and near the mountains along and east of the Divide. Well below average temperatures are expected Sunday. Confidence is high for below average temperatures for the remainder of the extended. The weather pattern becomes increasingly chaotic for the rest of the week in an overall trough. Medium range models show a shortwave trough pulling south/southeast out of southwest Canada Monday into the Pacific Northwest/Northern Rockies. This system, combined with possibly some energy from the trough Saturday/Sunday retrograding westward, could bring periodic chances of mainly snow across much of the area as shortwaves/compact lows pull across the forecast area next week. Confidence is low on timing and location of snow and will broadbrush mainly low PoPs for now. && .AVIATION...For the 00Z TAFS through 00Z Saturday East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals A strong cold front will sweep south-southeast across much of area between 00Z and 06Z. In the wake of the cold front, expect strong north to northwest winds with lowering ceilings and a chance of snow. The best chance of persistent snow looks to be KCOD from around 02Z to 06Z and then KCPR from about 06Z to 12Z. Both these terminals will likely have MVFR/IFR conditions during those time frames. Other terminals will have the potential for some snow showers tonight with brief MVFR/IFR conditions possible. Improving conditions will occur from northwest to southeast from late tonight into Friday morning including the winds weakening by around sunrise in most areas. By midday Friday, most areas will be mostly clear with mainly light winds. Mountains will become obscured from north to south this evening with improving conditions late tonight into Friday morning. West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals Windy northwest to west winds will occur at area terminals except more south-southwest at KJAC. The strong winds will remain through much of the night, with the winds shifting more northerly at KJAC by around 06Z. KJAC could see wind gusts of 40 to 45 kts this evening. Snow showers will expand southeastward this evening. KJAC would be most impacted by this activity this evening, with a period of MVFR/IFR conditions probable. The rest of the terminals are expected to remain dry, with only an outside chance of snow showers at KBPI, KPNA and KRKs. Chances are too low to mention any VCSH for now. The system moves away late tonight into Friday morning, with decreasing cloudiness and weaken winds Friday. 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 202 PM MDT Thu Apr 8 2021 A cold front will cross the area tonight and bring strong winds to many areas. Some rain showers will change to snow showers with a few inches of accumulation possible in the mountains and possibly portions of Johnson and Natrona counties. Wind will decrease Friday, as high pressure builds into the area with all areas having dry conditions by Friday afternoon. Relative humidity will fall into the teens across southern Wyoming Friday afternoon. Mixing and smoke dispersal will range from poor across the north to good to very good elsewhere. && .RIW WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...Hattings LONG TERM...Murrell AVIATION...Murrell FIRE WEATHER...Hattings
Hazardous Weather Outlook National Weather Service Riverton WY 129 PM MDT Thu Apr 8 2021 WYZ001>020-022>030-091930- 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- 129 PM MDT Thu Apr 8 2021 This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Tonight. Strong to gusty winds for many areas this afternoon into tonight. A period of snow is likely for northern Wyoming and the Interstate 25 corridor. Please see forecasts and Special Weather Statements for details. .DAYS TWO THROUGH SEVEN...Thursday through Monday. Saturday...Elevated fire conditions possible over the central and southern portion of the state. .SPOTTER INFORMATION STATEMENT... Spotters are urged to report snowfall amounts.
Special Weather Statement National Weather Service Riverton WY 1233 PM MDT Thu Apr 8 2021 WYZ001-002-012-090600- Yellowstone National Park-Absaroka Mountains- Teton and Gros Ventre Mountains- Including the cities of Lake, Mammoth, and Old Faithful 1233 PM MDT Thu Apr 8 2021 ...Snow and wind returning this afternoon and evening... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...Snow and wind. Snow accumulations of 2 to 4 inches with locally higher amounts. Winds gusting as high as 50 to 60 mph in the higher terrain. * WHERE...Yellowstone National Park, Absaroka, Teton and Gros Ventre Mountains. * WHEN...This Afternoon through early Friday morning. * ADDITIONAL DETAILS...Use caution when traveling. Roads will be slick and snow covered at times. WYZ010-011-090600- Northeast Johnson County-Southeast Johnson County- Including the cities of Buffalo and Kaycee 1233 PM MDT Thu Apr 8 2021 * WHAT...Snow and wind expected. A coating to an inch or two of snow possible. Winds becoming northwest an increasing to 20 to 30 mph with gusts to 50 to 55 mph. * WHERE...Johnson and Natrona Counties. * WHEN...Tonight through early Friday morning. * ADDITIONAL DETAILS...Use caution when traveling. Roads will be slick and snow covered at times and visibility may be strongly reduced in blowing snow. WYZ019-026>030-090600- Green Mountains and Rattlesnake Range-Upper Green River Basin- South Lincoln County-Rock Springs and Green River-Flaming Gorge- East Sweetwater County- Including the cities of Jeffrey City, La Barge, Big Piney, Farson, Kemmerer, Cokeville, Rock Springs, Green River, and Wamsutter 1233 PM MDT Thu Apr 8 2021 ...Gusty Winds Expected This Afternoon and Tonight... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...Wind becoming west to northwest and increasing to 20 to 30 mph with gusts to around 50 mph. * WHERE...Sweetwater, Sublette, southern Lincoln, southern Fremont and southern Natrona counties. * WHEN...This afternoon into tonight. WYZ008-009-090600- Bighorn Mountains West-Bighorn Mountains Southeast- 1233 PM MDT Thu Apr 8 2021 * WHAT...Snow. Snow accumulations of 3 to 5 inches with locally higher amounts. Wind may gust to around 50 mph across the higher terrain. * WHERE...Bighorn Mountains. * WHEN...Tonight through Friday morning. * ADDITIONAL DETAILS...Use caution when traveling. Roads will be slick and snow covered at times and visibility may be strongly reduced in blowing snow. WYZ003>007-090600- Cody Foothills-North Big Horn Basin-Southwest Big Horn Basin- Southeast Big Horn Basin-Owl Creek and Bridger Mountains- Including the cities of Clark, Cody, Meeteetse, Basin, Greybull, Lovell, Powell, Shell, Thermopolis, Ten Sleep, and Worland 1233 PM MDT Thu Apr 8 2021 ...Strong Wind Returning later this afternoon and tonight... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...Northwest wind increasing to 20 to 30 mph with gusts to around 50 mph. Visibility may be briefly reduced in snow showers. * WHERE...Cody Foothills and Big Horn Basin. The strongest wind will be in Big Horn County. * WHEN...Later this afternoon into tonight. * ADDITIONAL DETAILS...Motorists should watch for strong cross winds. Watch for rapid changes in visibility and locally slick roads. WYZ020-022-090600- Natrona County Lower Elevations-Casper Mountain- Including the city of Casper 1233 PM MDT Thu Apr 8 2021 ...Snow returning tonight and early tomorrow... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...Periods of snow. Accumulations of 1 to 3 inches in the lower elevations and 3 to 5 inches on Casper Mountain. * WHERE...Natrona County. * WHEN...Later tonight into Friday morning. * ADDITIONAL DETAILS...Use caution when traveling. Roads will be slick and snow covered at times. WYZ016>018-090600- Upper Wind River Basin-Wind River Basin-Lander Foothills- Including the cities of Dubois, Riverton, Shoshoni, and Lander 1233 PM MDT Thu Apr 8 2021 ...Gusty to strong wind later this afternoon and tonight... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...Northwest wind increasing to 20 to 30 mph with gusts to around 50 mph. * WHERE...Wind River Basin and Lander Foothills. * WHEN...Later this afternoon into tonight. * ADDITIONAL DETAILS...Motorists should watch for strong cross winds, especially those with high profile vehicles and towing light trailers. WYZ013-090600- Jackson Hole- Including the city of Jackson 1233 PM MDT Thu Apr 8 2021 ...Strong wind and snow showers this afternoon and tonight... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...Wind increasing to 20 to 30 mph with gusts to 50 to 55 mph. A period of rain changing to snow is possible late this afternoon and evening. * WHERE...Jackson Valley. * WHEN...Later this afternoon into this evening. * ADDITIONAL DETAILS...Motorists should watch for strong cross winds, especially those with high profile vehicles and towing light trailers. Slick roads are possible with any snow showers after sunset.
The national radar mosaic for the moment the first event began.
4 high wind. Local standard time, as filed.
High wind gusts were reported across most of northern Johnson County. The maximum wind gust reported was 70 mph at the Johnson County airport.
A 58 mph wind gust was recorded at the Powell airport.
A maximum wind gust of 61 mph was reported at the Willow Creek RAWS site.
A maximum wind gust reported a 62 mph wind gust north of Kaycee, Wyoming.
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: 953547, 953545, 953546, 953548.