A cold front moved across Wyoming and brought high winds to Johnson County. Wind gusts around 60 mph were recorded at the Johnson County airport as well as along Interstate 90.
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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 cold front moved across Wyoming and brought high winds to Johnson County. Wind gusts around 60 mph were recorded at the Johnson County airport as well as along Interstate 90.
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 10, 10:13 AM MST, 1 hour 19 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 1113 AM MDT Fri Jul 10 2020 .SHORT TERM...This afternoon through Saturday night Hot and mainly dry conditions, with mostly clear skies, will be in place across the forecast area today. Critically low RH values will occur over all, but far western portions. A shortwave is currently moving over west-central MT this morning and will continue moving eastward through the day. The tail end of this trough could help initiate showers and thunderstorms over Yellowstone and the far northern end of the Absarokas this afternoon and evening. A channel jet of 90 to 110kt will be over the Cowboy State today, as well. The combination of the jet and shortwave will tighten the surface gradient and increase the winds across the area. West to northwest winds 20 to 25 mph, with gusts of 35 to 45 mph, will be commonplace over central and southern portions. Winds will begin to increase by 11 am across the south, as humidity levels quickly fall below critical levels. The winds in the western valleys will be lighter, but still gusty. Red Flag Warnings are in effect over central portions. Elevated fire conditions will occur over southern portions, where fuels haven't been deemed critical yet. Strong gusty winds will remain the main threat from the aforementioned thunderstorms. A weak cold front, associated with the shortwave trough, will make its way southward over areas east of the Divide through the afternoon. Winds will turn morning northerly behind the front, notably over Johnson and Natrona counties. Winds will subside, along with the thunderstorm threat, after sunset. The front will wash out, as it reaches the Divide late tonight. Similar conditions will return Saturday, with hot and dry conditions. Winds will be lighter across the area, but remain gusty over southern portions. RHs will remain critically low, with far western portions dropping into the upper teens to near 20 percent. As has been discussed for the last several days, this trend will continue into next week. Additional details on this will be discussed in the Long Term portion. .LONG TERM...Monday through Thursday Issued at 144 AM MDT Fri Jul 10 2020 Models continue to indicate the next longwave trough shearing off the top of the western ridge, bringing a little relief from the hot temperatures over the weekend. The "cold" pool associated with the trough will bring H7 temps down to 10 to 15C on Monday and 7 to 12C on Tuesday, which translates to highs generally in the mid to upper 80s Monday and the lower 80s for Tuesday. With a weak front in the vicinity and impulses sweeping east around the bottom of the trough, expect slightly more agitated weather, mainly on Tuesday for the northern counties. Models are differing on what the ridge does for the latter half of the week. EC draws the ridge back to the northeast, pushing the fast zonal flow farther north and returning the heat, while the GFS draws the ridge/trough coupling to the eastern US, leaving the fast zonal flow across the NW US. This keeps low confidence for heat and precip forecast for the latter half of the week. && .AVIATION...For the 18Z TAFS through 18Z Saturday VFR conditions will occur through the period. A gusty west wind will develop over most of the region this afternoon and continue through 02Z. A cold front will bring a wind shift to the north over northern WY around 21Z with this north wind moving into the central zones between 01Z and 03Z. Very isolated showers or storms will occur over the far north this afternoon with most of the activity out of the area by 01Z. Winds will decrease this evening, remaining light through Saturday morning. && .FIRE WEATHER... A weather system tracking across Montana will bring gusty winds to much of the area and, combined with low humidity and hot temperatures, will bring elevated to critical fire weather to much of the area. The exception will be far western portions, where humidity will be somewhat higher. A Haines index of 5 to 6 will be in place across all but far northern/northwestern portions this afternoon. There will be a chance for dry thunderstorms over zones 140 and 286 this afternoon. && .RIW WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 8 PM MDT this evening for WYZ280>283-285- 288-300. && SHORT TERM...LaVoie LONG TERM...Straub AVIATION...Myers/LaVoie FIRE WEATHER...Hattings/LaVoie
Hazardous Weather Outlook National Weather Service Riverton WY 735 PM MDT Thu Jul 9 2020 WYZ001>020-022>030-110145- 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- 735 PM MDT Thu Jul 9 2020 ...Red Flag Warnings in portions of central Wyoming for Friday... .DAY ONE...Tonight. No hazardous weather is expected for the period. .DAYS TWO THROUGH SEVEN...Friday through Wednesday. Friday...Elevated to critical fire weather conditions over much of the area except for the far west. Sunday and Monday...Elevated to possibly critical fire weather conditions over much of the area except for the far west. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed today.
The national radar mosaic for the moment the first event began.
1 high wind. Local standard time, as filed.
A wind gust of 60 mph was recorded at the Johnson County airport. A couple of locations along Interstate 90 also reported wind gusts of 60 mph.
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, July 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: 899513.