Strong crosswinds were measured along Interstate 80 between Laramie and Rawlins during two time periods on the 19th: early in the morning and during the early evening.
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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 CYS wrote it up.
Strong crosswinds were measured along Interstate 80 between Laramie and Rawlins during two time periods on the 19th: early in the morning and during the early evening.
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 Cheyenne, WY wrote its last area forecast discussion before the first event at Sep 18, 10:50 PM MST, 3 hours 20 minutes earlier.
Area Forecast Discussion National Weather Service Cheyenne WY 1150 PM MDT Sat Sep 18 2021 .UPDATE... Issued at 750 PM MDT Sat Sep 18 2021 Updated forecast to allow the Red Flag Warning to expire on time tonight. It will continue to be breezy to locally windy as a Pacific cold front approaches the area. Will have to keep an eye on the wind prone areas with favorable conditions for west to southwest gusts of 45 to 55 mph tonight and early Sunday. Observations and current radar show a few sprinkles and showers across the area, so increased POP this evening for mainly southeast Wyoming. && .SHORT TERM...(This evening through Monday night) Issued at 230 PM MDT Sat Sep 18 2021 Temperatures today are pushing upper 80s and 90s through the afternoon with gusty winds 30 to 40 mph across most of southeast Wyoming with lighter winds in the Nebraska panhandle. The forecast has been consistent the last few days with temperatures tomorrow being seasonably warm (70s to 80s) with gusty winds (20 to 30 mph) continuing until a trough begins to make its way into southeast Wyoming Sunday evening, bringing widespread chances for rain and mountain snow showers Sunday evening through Monday afternoon, and dropping the temperatures into the 30s and 40s Sunday night with high temperatures Monday only in the 50s to 60s. The coldest temperatures will be Monday night after the trough has moved through with frost to even a light freeze being very possible. .LONG TERM...(Tuesday through Saturday) Issued at 230 PM MDT Sat Sep 18 2021 Pattern transitioning back to a warm/dry pattern with the departure of the shortwave trough moving east Tuesday morning. Upper ridge over the Pacific Northwest shifts east into the Rockies with warming upper levels through Wednesday. Fast moving shortwave moves through Montana Thursday that could give us increased winds and possible fire weather concerns during the day Thursday. Humidity definitely low Thursday afternoon...so fire weather concerns are definitely there. Next chance for any possible precipitation looks to be next weekend as upper ridge axis shifts east and a strong Pacific shortwave moves into the Pacific Northwest. Until then...warm and dry. && .AVIATION...(For the 06Z TAFS through 06Z Sunday night) Issued at 1145 PM MDT Sat Sep 18 2021 VFR conditions with BKN to OVC mid-level clouds across much of southeast Wyoming and western Nebraska. Gusty winds are expected through the night for SE WY terminals with mountain wave activity developing overnight. Gusty winds are expected to continue into Sunday afternoon with scattered showers possible in the evening. && .FIRE WEATHER... Issued at 230 PM MDT Sat Sep 18 2021 Tomorrow, Sunday, is forecast to be dry for much of the morning with chances for rain and mountain snow showers increasing after noon. There is a good chance for wetting rains and much cooler temperatures with this system, limiting the fire weather concerns until at least Wednesday. Wednesday through the end of the week is forecast to be seasonably warm and dry, so if gustier winds are present, there will be some elevated fire weather concerns, primarily for areas along and west of the Laramie Range. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && UPDATE...TJT SHORT TERM...LK LONG TERM...GCC AVIATION...MB FIRE WEATHER...LK
Hazardous Weather Outlook National Weather Service Cheyenne WY 810 PM MDT Sat Sep 18 2021 NEZ002-003-019>021-054-055-095-096-WYZ101>105-107-108-111>114-118- 119-200215- Dawes County-Box Butte County-Scotts Bluff County-Banner County- Morrill County-Kimball County-Cheyenne County- Northern Sioux County-Southern Sioux County- Converse County Lower Elevations-Niobrara County- North Laramie Range-Ferris/Seminoe/Shirley Mountains- Shirley Basin-East Platte County-Goshen County- Southwest Carbon County-Sierra Madre Range- Upper North Platte River Basin-Snowy Range-Central Laramie County- East Laramie County- 810 PM MDT Sat Sep 18 2021 This hazardous weather outlook is for portions of panhandle Nebraska...east central Wyoming...south central Wyoming and southeast Wyoming. .DAY ONE...TONIGHT No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY An abrupt change to cooler temperatures is expected late this weekend into early next week. Overnight lows are forecast to drop into the upper 20s to 30s, especially in the mountain valleys Sunday and Monday night. Be prepared to take action to protect sensitive plants from frost and a possible light freeze. .Spotter information statement... Spotter activation will not be required at this time. WYZ106-109-110-115>117-200215- Central Laramie Range and Southwest Platte County- Central Carbon County-North Snowy Range Foothills-Laramie Valley- South Laramie Range-South Laramie Range Foothills- 810 PM MDT Sat Sep 18 2021 This hazardous weather outlook is for portions of south central Wyoming and southeast Wyoming. .DAY ONE...TONIGHT Occasional strong wind gusts are possible tonight, mainly in the wind prone areas of southeast Wyoming. West to southwest winds may gust between 45 to 55 MPH after midnight through early Sunday morning. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY An abrupt change to cooler temperatures is expected late this weekend into early next week. Overnight lows are forecast to drop into the upper 20s to 30s, especially in the mountain valleys Sunday and Monday night. Be prepared to take action to protect sensitive plants from frost and a possible light freeze. .Spotter information statement... Spotter activation will not be required at this time.
The national radar mosaic for the moment the first event began.
1 high wind. Local standard time, as filed.
Multiple WYDOT mesonet stations recorded wind gusts early in the morning and early in the evening of the 19th. WYDOT mesonet station WY18 - Halleck Ridge along Interstate 80 measured maximum wind gust.
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, September 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: 977501.