A shower moving off of the Bighorn Range collapsed near Buffalo and produced strong winds. At the Johnson County airport, a maximum wind gust of 67 mph was recorded.
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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 shower moving off of the Bighorn Range collapsed near Buffalo and produced strong winds. At the Johnson County airport, a maximum wind gust of 67 mph was recorded.
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 Aug 6, 4:30 PM MST, 35 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 530 PM MDT Thu Aug 6 2020 .SHORT TERM...(This evening through Friday night) Issued at 148 PM MDT Thu Aug 6 2020 The midlevel shortwave continues to sweep northeastward around the periphery of the ridge to the east. This is sparking showers and a few thunderstorms across central and northern WY, which will continue through the peak heating hours before waning this evening. Any thunderstorms that form will be capable of producing very gusty winds as they pass. This pattern looks to continue Friday with the warm and dry southwesterly flow continuing. Showers and thunderstorms will again develop along the higher elevations, but without the shortwave in the vicinity, instability will be less, limiting the overall amount of showers in the region. .LONG TERM...(Saturday through Thursday) Issued at 148 PM MDT Thu Aug 6 2020 Mid-level flow will become more zonal for the weekend, with decreased convection chances across the area. Thus, a dry weekend is expected, although as usual a few isolated showers or thunderstorms cannot be ruled out, especially across higher terrain. Wind should be less of a factor during the weekend as well. A dry cold front will push into northern Wyoming Sunday, bringing afternoon temperatures down by 5-10 degrees across northern and eastern areas. The dry, westerly flow will continue at least through Tuesday, with little chance of precip across the area. On Wednesday models diverge a bit, but it does look like a wave may impact the CWA, possibly bringing increased rain chances across the west and north. Temperatures next week will not fluctuate very much and look to be generally near or a few degrees above normal. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 528 PM MDT Thu Aug 6 2020 VFR conditions expected at all terminals through the period. Ongoing convection will end around 02z, leaving the the rest of the period dry at terminals through Friday morning. Isolated showers are again expected over northern areas Friday afternoon, as well as a gusty southwest wind impacting southern and central terminals. && .FIRE WEATHER... Issued AT 148 PM MDT Thu Aug 6 2020 Red Flag Warnings continue across the southern portions of the state today, due to very low humidity and gusty southwest winds. Scattered showers have begun to form for central and northern WY, which may produce gusty winds and occasional lightning. Another very dry day expected on Friday, but winds will generally be lighter than today. && .RIW WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 8 PM MDT this evening for WYZ277>279-288- 289-414. && SHORT TERM...Straub LONG TERM...Myers AVIATION...Myers FIRE WEATHER...Straub
Hazardous Weather Outlook National Weather Service Riverton WY 212 AM MDT Thu Aug 6 2020 WYZ001>020-022>030-071000- 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- 212 AM MDT Thu Aug 6 2020 ...Red Flag Warning for portions of central and southern Wyoming... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight. Critical fire weather in portions of central and southern Wyoming. Please see Red Flag Warning for details. Isolated afternoon and evening thunderstorms expected. .DAYS TWO THROUGH SEVEN...Friday through Wednesday. Friday...Isolated thunderstorms north. Elevated fire concerns in parts of the central and south. Monday and Tuesday...Isolated afternoon and evening thunderstorms. .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
311 PM MDT Thu Aug 6 2020
WYZ020-022-062145-
Casper Mountain-Natrona County Lower Elevations-
311 PM MDT Thu Aug 6 2020
...SIGNIFICANT WEATHER ADVISORY FOR EAST CENTRAL NATRONA COUNTY UNTIL
345 PM MDT...
At 309 PM MDT, Doppler radar was tracking a strong thunderstorm over
Casper Airport, or about 5 miles northwest of Casper, moving east
northeast at 20 mph.
Wind gusts up to 50 mph will be possible with this storm. The strong
winds will impact much of Casper even where little or no rain occurs.
This strong thunderstorm will be near...
Bar Nunn around 320 PM MDT.
Casper and Evansville around 325 PM MDT.
This includes Interstate 25 between mile markers 176 and 196.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Infrequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
&&
LAT...LON 4277 10608 4274 10646 4293 10653 4303 10609
4297 10607 4283 10607
TIME...MOT...LOC 2109Z 256DEG 19KT 4285 10640
21Special Weather Statement National Weather Service Riverton WY 320 PM MDT Thu Aug 6 2020 WYZ003-004-062200- North Big Horn Basin-Cody Foothills- 320 PM MDT Thu Aug 6 2020 ...SIGNIFICANT WEATHER ADVISORY FOR WEST CENTRAL BIG HORN AND EAST CENTRAL PARK COUNTIES UNTIL 400 PM MDT... At 319 PM MDT, Doppler radar was tracking a strong thunderstorm 12 miles east of Meeteetse Rim, which is 16 miles northeast of Meeteetse, moving northeast at 25 mph. Wind gusts of 50 to 55 mph will be possible with this storm. The strong winds can occur well away from the thunderstorm where no rain is falling. This storm will remain over mainly rural areas of west central Big Horn and east central Park Counties, including the following locations...Emblem and Burlington. PRECAUTIONARY/PREPAREDNESS ACTIONS... Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. && LAT...LON 4417 10862 4427 10883 4468 10852 4453 10821 TIME...MOT...LOC 2119Z 213DEG 20KT 4432 10864 21
Special Weather Statement
National Weather Service Riverton WY
326 PM MDT Thu Aug 6 2020
WYZ006-062200-
Southeast Big Horn Basin-
326 PM MDT Thu Aug 6 2020
...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN WASHAKIE COUNTY
UNTIL 400 PM MDT...
At 325 PM MDT, Doppler radar was tracking a strong thunderstorm 10
miles west of Worland, moving northeast at 20 mph.
Wind gusts of 50 to 55 mph will be possible with this storm. The
strong winds can occur well away from any rainfall.
This strong thunderstorm will be near...
Wyoming Boys School around 335 PM MDT.
Worland around 350 PM MDT.
Other locations impacted by this storm include Washakie County
Fairgrounds.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Infrequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
&&
LAT...LON 4415 10778 4383 10797 4396 10836 4417 10823
4417 10782
TIME...MOT...LOC 2125Z 213DEG 19KT 4398 10817
21Special Weather Statement
National Weather Service Riverton WY
354 PM MDT Thu Aug 6 2020
WYZ004-006-062230-
North Big Horn Basin-Southeast Big Horn Basin-
354 PM MDT Thu Aug 6 2020
...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL BIG HORN AND NORTH
CENTRAL WASHAKIE COUNTIES UNTIL 430 PM MDT...
At 352 PM MDT, Doppler radar was tracking a strong thunderstorm over
Worland, moving northeast at 35 mph.
Wind gusts of 50 to 55 mph will be possible with this storm. The
strong winds could occur well away from the rainfall. Also, pea size
hail is possible.
This strong thunderstorm will be near...
Hyattville around 430 PM MDT.
Other locations impacted by this storm include Washakie County
Fairgrounds.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
&&
LAT...LON 4425 10748 4422 10747 4382 10798 4393 10822
4434 10794
TIME...MOT...LOC 2152Z 216DEG 32KT 4399 10802
21The Riverton/Lander radar (KRIW), 202 km away, was scanning. The volume nearest the first event began at 00:05 UTC.
1 thunderstorm wind. Local standard time, as filed.
A maximum wind gust of 67 mph was recorded at the Johnson County airport near Buffalo.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2020Every state in 2020This day in weather historyWarnings in Wyoming, August 2020
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: 913116.