Strong downburst winds associated with thunderstorms occurred across Carbon, Albany and Laramie Counties in southeast Wyoming the afternoon of 13 July 2020.
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.
Strong downburst winds associated with thunderstorms occurred across Carbon, Albany and Laramie Counties in southeast Wyoming the afternoon of 13 July 2020.
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 Jul 13, 12:57 PM MST, 9 minutes earlier.
Area Forecast Discussion National Weather Service Cheyenne WY 157 PM MDT Mon Jul 13 2020 .SHORT TERM...(This evening through Wednesday night) Issued at 154 PM MDT Mon Jul 13 2020 Tonight...Agree with the Storm Prediction Center depiction of marginal risk this evening over much of our counties, with a slight risk mainly east of a Kimball to Chadron line. Combination of decent instability and wind shear points to a few strong to severe thunderstorms through this evening mainly over our Nebraska counties. As a cold front drifts southward overnight, the chance for showers will continue after midnight north of a Douglas to Scottsbluff line. Tuesday...Quite a variance in the models with respect to maximum temperatures with the NAM MOS much cooler than the GFS MOS. Will definitely see cooler temperatures with surface high pressure over Nebraska producing cool upslope and considerable low clouds east of I-25, though hard to believe it will be as cool as the NAM MOS shows, thus will split the difference between the two models. Isolated to scattered afternoon showers and thunderstorms mainly over the I-25 corridor. Tuesday night...A passing shortwave trough aloft in northwest flow and considerable moisture will help produce scattered showers and thunderstorms mainly east of I-25. Wednesday/Wednesday night...Warming trend begins with more sunshine and an airmass modification. Looks like enough low and mid level moisture for isolated afternoon thunderstorms over far southeast Wyoming. .LONG TERM...(Thursday through Monday) Issued at 154 PM MDT Mon Jul 13 2020 Thursday...Drier air works in at low and mid levels, and with warm temperatures aloft, chances for showers and thunderstorms appear minimal. Friday/Saturday...Hot and mainly dry conditions prevail under westerly flow aloft, and with limited low and mid level moisture and warm temperatures aloft acting to cap the atmosphere. Sunday/Monday...Heights aloft decrease along with increasing low and mid level moisture, suggesting an increase in daily afternoon and evening shower and thunderstorm coverage. Temperatures will cool a bit with the extra cloud cover and increased coverage of showers and thunderstorms. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 1145 AM MDT Mon Jul 13 2020 Aviation conditions will continue in VFR for all Wyoming and Nebraska sites. Thunderstorms, which will be more focused on the Nebraska panhandle, will arrive as early as 19Z and end around 07Z. Additionally, wind gust will increase this afternoon for all site in Wyoming and Nebraska panhandle. Wyoming sites may receive up to 40mph wind gust; Nebraska sites also may see up to 30 mph especially with severe storm focused on the panhandle. Nebraska sites will stay in VFR conditions until 11Z; overcast skies will bring visibility and ceilings down to MVFR conditions till 18Z. Follow the next AFD for updates. && .FIRE WEATHER... Issued at 154 PM MDT Mon Jul 13 2020 Low afternoon humidities will prevail across Carbon and Albany Counties Tuesday and Wednesday, spreading eastward across much of the district Thursday through Saturday. Some humidity recovery Sunday and Monday, except over Carbon County. The windiest days will be Tuesday and Friday. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && SHORT TERM...RUBIN LONG TERM...RUBIN AVIATION...AW FIRE WEATHER...RUBIN
Hazardous Weather Outlook National Weather Service Cheyenne WY 424 AM MDT Mon Jul 13 2020 NEZ002-003-019>021-054-055-095-096-WYZ101>103-105>108-115>119- 141030- Dawes-Box Butte-Scotts Bluff County-Banner County-Morrill- Kimball County-Cheyenne-North Sioux-South Sioux- Converse County Lower Elevations-Niobrara County- North Laramie Range-Shirley Basin- Central Laramie Range and Southwest Platte County- East Platte County-Goshen County-Laramie Valley- South Laramie Range-South Laramie Range Foothills- Central Laramie County-East Laramie County- 424 AM MDT Mon Jul 13 2020 This hazardous weather outlook is for portions of panhandle Nebraska...western Nebraska...east central Wyoming...south central Wyoming and southeast Wyoming. .DAY ONE...TODAY AND TONIGHT Scattered to numerous showers and thunderstorms are expected over the area this afternoon and tonight. Some thunderstorms may become strong to severe mainly over the Panhandle with hail and gusty winds the main threat. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY The probability for widespread hazardous weather is low. .Spotter information statement... Spotter activation is not expected. WYZ104-109>114-141030- Ferris/Seminoe/Shirley Mountains-Central Carbon County- North Snowy Range Foothills-Southwest Carbon County- Sierra Madre Range-Upper North Platte River Basin-Snowy Range- 424 AM MDT Mon Jul 13 2020 This hazardous weather outlook is for portions of south central Wyoming. .DAY ONE...TODAY AND TONIGHT Widely scattered showers and thunderstorms are possible this afternoon and evening. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY The probability for widespread hazardous weather is low. .Spotter information statement... Spotter activation will not be needed.
Special Weather Statement National Weather Service Cheyenne WY 1252 PM MDT Mon Jul 13 2020 WYZ118-119-131915- Central Laramie County WY-East Laramie County WY- 1252 PM MDT Mon Jul 13 2020 ...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL LARAMIE COUNTY UNTIL 115 PM MDT... At 1251 PM MDT, Doppler radar was tracking a strong thunderstorm 7 miles east of Cheyenne, moving east at 35 mph. Half inch hail and winds in excess of 40 mph will be possible with this storm. Locations impacted include... Cheyenne, Burns, Hillsdale and Ranchettes. This includes Interstate 80 in Wyoming between mile markers 367 and 387. LAT...LON 4110 10473 4120 10472 4131 10433 4107 10432 TIME...MOT...LOC 1851Z 262DEG 32KT 4116 10465 Mokry
Special Weather Statement
National Weather Service Cheyenne WY
113 PM MDT Mon Jul 13 2020
WYZ110-115-131930-
North Snowy Range Foothills WY-Laramie Valley WY-
113 PM MDT Mon Jul 13 2020
...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL ALBANY COUNTY UNTIL 130
PM MDT...
At 113 PM MDT, Doppler radar was tracking a strong thunderstorm 13
miles southwest of Bosler, or 21 miles northwest of Laramie, moving
east at 35 mph.
Half inch hail and winds in excess of 40 mph will be possible with
this storm.
This storm will remain over mainly rural areas of central Albany
County.
This includes Interstate 80 in Wyoming between mile markers 285 and
293.
LAT...LON 4144 10597 4146 10603 4153 10603 4157 10576
4141 10575
TIME...MOT...LOC 1913Z 269DEG 31KT 4149 10592
MokrySpecial Weather Statement
National Weather Service Cheyenne WY
115 PM MDT Mon Jul 13 2020
WYZ118-119-131945-
Central Laramie County WY-East Laramie County WY-
115 PM MDT Mon Jul 13 2020
...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN LARAMIE COUNTY UNTIL
145 PM MDT...
At 114 PM MDT, Doppler radar was tracking a strong thunderstorm near
Burns, or 20 miles east of Cheyenne, moving east at 35 mph.
Half inch hail and winds in excess of 40 mph will be possible with
this storm.
Locations impacted include...
Pine Bluffs, Burns, Hillsdale and Carpenter.
This includes Interstate 80 in Wyoming between mile markers 379 and
401.
LAT...LON 4102 10447 4108 10450 4126 10450 4126 10407
4102 10406
TIME...MOT...LOC 1914Z 269DEG 31KT 4115 10440
MokrySpecial Weather Statement
National Weather Service Cheyenne WY
116 PM MDT Mon Jul 13 2020
WYZ117-118-131930-
Central Laramie County WY-South Laramie Range Foothills WY-
116 PM MDT Mon Jul 13 2020
...SPECIAL WEATHER STATEMENT...
At 116 PM MDT, emergency management reported a strong thunderstorm
over Cheyenne, moving northeast at 30 mph.
Pea size hail and winds in excess of 30 mph will be possible with
this storm.
Locations impacted include...
Cheyenne, South Greeley, Frontier Park, Warren AFB, Ranchettes, Fox
Farm-College and South Greeley High.
This includes the following highways...
Interstate 25 in Wyoming between mile markers 11 and 12.
Interstate 80 in Wyoming between mile markers 361 and 372.
LAT...LON 4105 10470 4105 10478 4116 10486 4124 10471
4120 10459
TIME...MOT...LOC 1916Z 228DEG 25KT 4113 10476
MokrySpecial Weather Statement
National Weather Service Cheyenne WY
129 PM MDT Mon Jul 13 2020
WYZ115-131945-
Laramie Valley WY-
129 PM MDT Mon Jul 13 2020
...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL ALBANY COUNTY UNTIL 145
PM MDT...
At 129 PM MDT, Doppler radar was tracking a strong thunderstorm near
Bosler, or 16 miles northwest of Laramie, moving east at 35 mph.
Half inch hail and winds in excess of 40 mph will be possible with
this storm.
This storm will remain over mainly rural areas of central Albany
County.
LAT...LON 4145 10583 4151 10587 4155 10583 4159 10557
4143 10559
TIME...MOT...LOC 1929Z 259DEG 29KT 4150 10577
MokrySpecial Weather Statement
National Weather Service Cheyenne WY
139 PM MDT Mon Jul 13 2020
WYZ116-117-132000-
South Laramie Range WY-South Laramie Range Foothills WY-
139 PM MDT Mon Jul 13 2020
...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN ALBANY AND
NORTHWESTERN LARAMIE COUNTIES UNTIL 200 PM MDT...
At 139 PM MDT, Doppler radar was tracking a strong thunderstorm over
Horse Creek, or 19 miles east of Laramie, moving east at 35 mph.
Half inch hail and winds in excess of 40 mph will be possible with
this storm.
Locations impacted include...
Horse Creek.
LAT...LON 4135 10525 4138 10531 4142 10531 4145 10526
4150 10502 4133 10504
TIME...MOT...LOC 1939Z 266DEG 29KT 4140 10523
MokryThe Cheyenne radar (KCYS), 182 km away, was scanning. The volume nearest the first event began at 20:06 UTC.
20 thunderstorm wind. Local standard time, as filed.
Wyoming Department of Transportation site at Walcott Junction along Interstate 80 measured the reported wind speed.
Wyoming Department of Transportation site at mile marker 249 measured the reported wind speed.
Wyoming Department of Transportation site (WY18), Halleck Ridge measured the reported wind speed.
RAWS site at Cow Creek in southwestern Carbon County measured the reported wind speed.
Wyoming Department of Transportation site at Skyline (KSKL) measured the reported wind speed.
Wyoming Department of Transportation site at Foote Creek on Interstate 80 measured the reported wind speed.
Wyoming Department of Transportation site at Wagonhound on Interstate 80 measured the reported wind speed.
Mesonet station FW4499 Laramie measured the reported wind speed.
Wyoming Department of Transportation site at Pumpkin Vine measured the reported wind speed.
Wyoming Department of Transportation site at Vedauwoo (WY36) measured the reported wind speed.
Wyoming Department of Transportation site at Vedauwoo measured the reported wind speed.
Asos station at Laramie Airport (KLAR) measured the reported wind speed.
Union Pacific Railroad site at Harriman measured the reported wind speed.
Union Pacific Railroad site Dale measured the reported wind speed.
Union Pacific Railroad site at Emkay measured the reported wind speed.
Wyoming Department of Transportation site at Wildcat Trail along Interstate 80 measured the reported wind speed.
Wyoming Department of Transportation site at Otto along Interstate 80 measured the reported wind speed.
Wyoming Department of Transportation site at mile marker 353 along Interstate 80 measured the reported wind speed.
Wyoming Department of Transportation site at mile marker 353 along Interstate 80 measured the reported wind speed.
Reported winds measured at the Cheyenne Airport.
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: 896514, 896516, 896518, 896520, 896521, 896522, 896523, 896524, 896525, 896526, 896529, 896530, 896531, 896532, 896533, 896534, 896535, 896536, 896537, 896538.