A very strong ridge over the northern Rockies brought record high temperatures to much of western and central Wyoming. The highest temperature was 106 degrees at Worland on July 27th.
Every event with a place to put it; 7 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 very strong ridge over the northern Rockies brought record high temperatures to much of western and central Wyoming. The highest temperature was 106 degrees at Worland on July 27th. High temperatures over 100 degrees were recorded at many locations east of the Continental Divide during this period.
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 Jul 24, 9:35 PM MST, 2 hours 25 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 1035 PM MDT Sat Jul 24 2021 .SHORT TERM...This afternoon through Sunday night Issued at 1103 AM MDT Sat Jul 24 2021 Stagnant to light flow will continue as the main jetstream remains well north of the area. As the lack of any forcing flow continues, smoke will continue to filter into the region today. Isolated showers and maybe a thunderstorm is possible today across the eastern portions of Johnson, Sweetwater and Natrona counties, but with the continued lack of upper-level support, the thunderstorms should be short-lived. Any shower or storm that does develop, could produce outflows with gusts upwards of 40 mph. High temperatures will continue to be in the mid to upper 90s and with the smoke not allowing for a whole lot of radiational cooling overnight, decided to go a little bit warmer than guidance to reflect that. Still remaining quiet through Sunday, as the the jetstream remains north of the area, however, models are suggesting the building of a subtle ridge to end the weekend and start the work week. Weather- wise, still remaining hot, dry and smoky through the period. .LONG TERM...Monday through Saturday Overview...High pressure will be in control over the region through much of next week. Hot temperatures will continue through this time, with record highs possible Monday and Tuesday. Increasing chances for thunderstorms Tuesday and Wednesday, with widespread thunderstorms possible across the forecast area Thursday and Friday. Locally heavy rain will be the main threat due to above normal precipitable water (PWat) values and slow storm motions. Synopsis...A ridge will build over the region Monday, becoming a strong broad ridge by Wednesday. The center of the high will start over WY Monday, shifting to the NE/KS/CO area by Wednesday. Hot and dry conditions remain in the forecast Monday, with record highs possible Monday and Tuesday. A surge of monsoonal moisture over the Great Basin will begin to creep into far western portions of the state Tuesday, as the high starts its shift to the southeast. PWats will be 125 to 175% of normal in this area. This, in addition to weak flow at 700mb, will mean the main threat with any convection will be locally heavy rain. By Wednesday, any thunderstorms will occur along the periphery of the high, namely, over southern, western and northern portions. Higher Pwats approaching 200% of normal could reach the forecast area by Thursday. More of the forecast area will be impacted Thursday and Friday, as the center of the upper high continues its shift over the Central Plains. Temperatures should cool slightly after Wednesday, with the chances for convection across the area. && .AVIATION...For the 06Z TAFS through 06Z Monday Issued at 1030 PM MDT Sat Jul 24 2021 VFR conditions will prevail at the terminal sites. Visibility will be reduced over the region by smoke and expect areas of MVFR conditions through the period and partial mountain obscuration. Isolated showers or storms will be possible after 20Z over or near the central WY mountains until 03Z Monday. Other isolated showers or storms may occur from vcnty KRKS to KCPR after 21Z through 03Z Monday. Wind gusts around 35 knots will be possible near any storms. 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 1103 AM MDT Sat Jul 24 2021 High pressure will continue to dominate the region today. An isolated shower or two may be possible across the eastern portions of Sweetwater, Natrona and Johnson counties. Any shower or storm that develops could produce outflow wind gusts upwards of 40 mph. Light to moderate winds are expected today with fair to good smoke dispersal this afternoon. Relative humidity will dip below 15 percent across the southwestern zones and most of the basins. && .RIW WATCHES/WARNINGS/ADVISORIES...NONE. && SHORT TERM...Vorst LONG TERM...LaVoie AVIATION...AR FIRE WEATHER...Vorst
Hazardous Weather Outlook National Weather Service Riverton WY 200 AM MDT Sat Jul 24 2021 WYZ001>020-022>030-251200- 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- 200 AM MDT Sat Jul 24 2021 This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight. Isolated afternoon and evening thunderstorms eastern areas. .DAYS TWO THROUGH SEVEN...Sunday through Friday. Above average temperatures, but the warmest days look to be Tuesday and Wednesday when high temperatures might be 10 to 15 degrees above average. Wednesday through Saturday...Isolated to scattered afternoon and evening thunderstorms. Locally heavy rainfall is possible. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report significant weather conditions according to standard operating procedures.
The national radar mosaic for the moment the first event began.
7 heat. Local standard time, as filed.
Record high temperatures of 102 and 105 were recorded at South Big Horn County Airport on July 26th and 27th, respectively.
A record high temperature of 106 was recorded at Worland Municipal Airport on July 27th.
The recorded high temperature at Central Wyoming Regional Airport set a record three days in a row. Record high temperatures of 96, 97 and 100 were recorded on July 25th, 26th and 27th, respectively.
The Johnson County Airport in Buffalo set record highs three days in a row. Record high temperatures of 97, 97 and 102 were recorded on July 25th, 26th and 27th, respectively.
Daily high temperatures at Southwest Wyoming Regional Airport set records on July 26th and 27th. High temperatures of 93 and 92 were recorded, respectively.
A record high temperature of 100 degrees was set at Casper-Natrona County International Airport just west of Casper.
The thermometer hit a new record high temperature of 98 degrees at Hunt Field in Lander July 26th.
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, July 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: 971326, 971327, 971328, 971329, 971330, 971331, 971332.