Severe downburst winds were reported at a few locations in southeast Wyoming on 7 August.
Every event with a place to put it. 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 CYS wrote it up.
Severe downburst winds were reported at a few locations in southeast Wyoming on 7 August.
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 Aug 7, 11:04 AM MST, 28 minutes earlier.
Area Forecast Discussion National Weather Service Cheyenne WY 1204 PM MDT Mon Aug 7 2023 .UPDATE... Issued at 1203 PM MDT Mon Aug 7 2023 Latest GOES WV imagery shows a leading shortwave moving east across western WY ahead of the large upper level trough digging into central OR. Have seen CI this morning over northern CO and south- central WY where slightly better upper level dynamics are present associated with the 80-90 kt 250mb jet crossing the central Rockies. Mainly could see gusty winds with these initial storms along the I- 80 corridor in Carbon and Albany Co early this afternoon as the atmosphere continues to destabilize. Numerous WYDOT mesonet sensors have reported gusts 35-40 mph with these initial storms. Will continue to see increasing coverage of storms along the CO/WY border early this afternoon before spreading east towards the NE Panhandle. Forecast soundings show fairly dry low-levels along and west of the Laramie Range supporting high-based storms and the potential for strong outflow winds. Latest observations have the dryline positioned near I-25 with KCYS recently turning out of the NW with dew points dropping 10F degrees to 39F. However, a WYDOT sensor along I-25 ~20 miles north of Cheyenne still sits at a dew point of 49F degrees. CAMs continue to show numerous storms developing over Laramie Co by 2-3 PM MDT moving east towards better instability east of the dryline. Latest RAP continue to show 1500 J/kg in eastern WY with a well of 2000+ J/kg in the NE Panhandle making large hail a concern today. Hodographs are also fairly straight with mostly unidirectional shear, so expecting numerous storm splits that could lead to a messy setup limiting discrete cells. Will need to be mindful of any storms initially developing in northern CO as the Bunkers left-mover motion is towards the northeast at 30 kt. In addition to these initial storms along the I-80 corridor, CI has also begun along the Wind River Range closer to the upper level shortwave passing through today. CAMs track these storms eastward across central WY into our CWA as a second wave of storms late in the afternoon with another threat for strong winds and hail. && .SHORT TERM...(Today through Tuesday night) Issued at 305 AM MDT Mon Aug 7 2023 Current surface analysis depicts the cold front, which dropped the temperatures across the region, has stalled out across the southern CONUS, as surface high pressure continues to move into the Intermountain West from the Pacific Northwest. Some showers and thunderstorms have continued overnight, with recent radar imagery indicating showery activity across the I-25 corridor and into the Nebraska Panhandle. Most of the impactful weather has continued to subside overnight, with some gusty winds observed near Bordeaux around 30 mph in the vicinity of shower activity. Another active day expected for the early afternoon hours, with several shortwave disturbances propagating within the flow. HiRes model guidance has been consistent, with MLCAPEs hovering around 1500 to 2000 J/kg, 45 to 55 kts of 0-6 km shear, decent moisture advection with up to an inch PWATs pushing into the Nebraska Panhandle, 700- 500mb Lapse Rates around 8.0C/km, and increasing SHIP parameters further eastward into the Panhandle. Confidence for severe weather is quite a bit higher for the Nebraska Panhandle, where current SPC Convective Outlooks place Marginal and Slight Risks of Severe Thunderstorms. However, possibilities still remain for severe thunderstorms into western Laramie County with the RAP model guidance placing some stronger cells across the I-25 corridor where decent shear and lift along the shortwave disturbances will take place. As a result, kept the chances for large hail and severe winds in place for Laramie, Goshen, and Platte County. Main threats for the day will include Large Hail and Damaging Winds, in addition to fairly straight hodographs which continue to support splitting storms and an isolated tornado risk in the right movers of the splitting storms. Severe weather chances continue into Tuesday, with a Marginal Risk of severe thunderstorms for the most eastern portion of Wyoming and a Slight Risk of Severe Thunderstorms for the Nebraska Panhandle. Low level southeasterly flow will help maintain dewpoints in the high-50s for the eastern most counties in the Nebraska Panhandle and mid-50s into Goshen County. All in all, Tuesday appears to be a repeat for what will occur later this afternoon, with thermodynamic profiles remaining very similar for both days. .LONG TERM...(Wednesday through Sunday) Issued at 305 AM MDT Mon Aug 7 2023 Exiting low pressure system will give way to drier weather for southeast Wyoming and Nebraska Panhandle Wednesday as a ridge of high pressure builds back into the area. Cooler than normal with highs in the 70s for much of southeast Wyoming and near 80 for the Panhandle. Could be breezy Thursday as a low pressure system tracks across Montana...a favorable pattern for breezy winds. The only areas to see any shower activity would be our western mountains. Associated cold front looks to drop south into the CWA Thursday evening into Friday morning with 700mb temperatures falling to 10 to 12C. Not much in the way of precip with this front. Best chances would be Carbon and Albany Counties where we have chance PoPs Friday afternoon/evening. Fairly warm for next weekend with 700mb temperatures up near +15C. 80s to low 90s pretty common across the CWA. Afternoon convection with these warmer temperatures and instability. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 1135 AM MDT Mon Aug 7 2023 Mainly VFR conditions expected across southeast Wyoming and the Nebraska panhandle. Primary weather hazards will be thunderstorms, however timing of the thunderstorms and confidence of when exactly they could pass a TAF terminal is low to medium at this time. AMDs are expected as more thunderstorms develop. Main storm activity should be east of the Nebraska panhandle by 02-04Z. Generally light wind overnight with areas of BR/FG possible near KCDR and KAIA. && .FIRE WEATHER... Issued at 305 AM MDT Mon Aug 7 2023 Little to no fire weather concerns for the start to the work week with several days of wetting rains leading to fuels remaining in green up. Could see some elevated fire weather concerns Thursday onward for Carbon County with minimum RH in the mid-teens and wind speeds increasing to around 25+ knots. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && UPDATE...MB SHORT TERM...MRD LONG TERM...GCC AVIATION...LEG FIRE WEATHER...MRD
Special Weather Statement
National Weather Service Cheyenne WY
1131 AM MDT Mon Aug 7 2023
WYZ109-110-113-114-071815-
Upper North Platte River Basin WY-North Snowy Range Foothills WY-
Central Carbon County WY-Snowy Range WY-
1131 AM MDT Mon Aug 7 2023
...A thunderstorm will impact portions of east central Carbon County
through 1215 PM MDT...
At 1130 AM MDT, Doppler radar was tracking a thunderstorm 11 miles
west of Elk Mountain, or 31 miles east of Rawlins, moving east at 35
mph.
HAZARD...Wind gusts up to 50 mph and pea size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor damage to outdoor objects is
possible.
Locations impacted include...
Elk Mountain and Arlington.
This includes Interstate 80 in Wyoming between mile markers 241 and
277.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4160 10675 4176 10672 4179 10610 4151 10613
TIME...MOT...LOC 1730Z 273DEG 30KT 4168 10663
MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 MPH
BrothersThe Cheyenne radar (KCYS), 90 km away, was scanning. The volume nearest the first event began at 18:30 UTC.
3 thunderstorm wind, 1 hail. Local standard time, as filed.
WYDOT sensor WY27 (Herrick Lane) reported thunderstorm wind gust of 60 mph.
WYDOT sensor at Vedauwoo reported thunderstorm wind gust of 58 mph.
UPR site EMKAY (UP226) reported this severe thunderstorm downburst wind.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2023Every state in 2023This day in weather historyWarnings in Wyoming, August 2023
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: 1108849, 1108850, 1108851, 1115636.