Three slowly moving thunderstorms merged over Midwest and brought large amounts of hail and street flooding. 5 inches of precipitation with rain and melting hail.
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 RIW wrote it up.
Three slowly moving thunderstorms merged over Midwest and brought large amounts of hail and street flooding. A rain gauge measured over 2.5 inches of precipitation with rain and melting hail. The hail flowed into a wash and drifted up to four feet in some areas. Flooding was also noted in Salt Creek Oil Field as well as in portions of Midwest.
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 Jun 23, 1:42 PM MST, 2 hours 28 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 242 PM MDT Sat Jun 23 2018 .SHORT TERM...(This evening through Tuesday) Issued at 233 PM MDT Sat Jun 23 2018 A Pacific low pressure trough moving through the Northern Rockies will bring afternoon and evening showers with isolated thunderstorms, most numerous in the north and central tonight, decreasing in coverage on Sunday. Heavy thunderstorms rains may cause flooding across the north, central and east through Sunday afternoon. Temperatures will decrease with increasing relative humidity. The south will be mainly dry with breezy to windy areas and lower relative humidity. With high pressure ridging over the west and decreasing west flow aloft, drying will occur with warming Monday and Tuesday. .LONG TERM...(Tuesday night through Saturday) Issued at 233 PM MDT Sat Jun 23 2018 West flow aloft will bring dry conditions Wednesday and Thursday with some limited moisture and instability increasing across the north Friday and Saturday for limited showers and thunderstorms. Temperatures will continue to warm through Thursday then cool Friday and Saturday. && .AVIATION...(For the 00Z TAFS through 00Z Monday) Issued at 233 PM MDT Sat Jun 23 2018 VFR conditions expected at all terminals through the forecast period with a few exceptions. Depending upon rainfall and a moist boundary layer, there could be a period of MVFR ceilings at KCPR and KWRL between 08Z-15Z/Sunday. Confidence is still low and a prevailing group is not included with this forecast issuance. However, a TEMPO group or prevailing group may be needed with 06Z/Sunday issuance. Brief MVFR conditions possible east of the Continental Divide with strongest convection between 21Z/Saturday and 03Z/Sunday. Mountain top obscurations will continue through at least 12Z/Sunday across the northwest and north. Upper low over western Montana will slowly progress southeast Saturday night and Sunday morning. The showers and thunderstorms associated with this system will push south as well with the most widespread convection between 21Z/Saturday and 03Z/Sunday. Coverage and intensity of showers and storms will decrease after that time but will continue through the night. Upper low will eventually set-up over western portions of South Dakota and Nebraska later Sunday. This will allow for lingering showers at KCPR and KWRL through at least Sunday morning. High pressure will push into southwest Wyoming Sunday afternoon with dry conditions and less wind anticipated Sunday afternoon. Gusty west-northwest surface wind of 15-25kts Saturday afternoon ahead of a south-moving cold front. This front will reach a KLND-KCPR line by 01Z/Sunday with gusty north wind in its wake through 06Z/Sunday. Surface winds will be much less at all terminals Sunday afternoon. 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 233 PM MDT Sat Jun 23 2018 A Pacific low pressure trough moving through the Northern Rockies will bring afternoon and evening showers with isolated thunderstorms, most numerous in the north and central tonight, decreasing in coverage on Sunday. Temperatures will decrease with increasing relative humidity. The south will be mainly dry with breezy to windy areas and lower relative humidity. The lower and mid levels will be unstable and well mixed Sunday and Monday with sufficient winds for excellent smoke dispersal in the afternoons. && .RIW WATCHES/WARNINGS/ADVISORIES... Flood Watch from 6 PM MDT this evening through Sunday afternoon for WYZ005>011-017-019-020-022. && SHORT TERM...Baker LONG TERM...Baker AVIATION...Jones FIRE WEATHER...Baker
Hazardous Weather Outlook National Weather Service Riverton WY 138 AM MDT Sat Jun 23 2018 WYZ001>020-022>030-241300- 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- 138 AM MDT Sat Jun 23 2018 ...Flood Watch is in effect from Saturday evening through Sunday afternoon for central and eastern portions... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight Saturday and Saturday night...Showers and thunderstorms will become more numerous by the afternoon and continue through the overnight hours. Localized flooding is possible Saturday night. .DAYS TWO THROUGH SEVEN...Sunday through Friday Sunday...Scattered showers with isolated thunderstorms, with locally heavy rain, will continue through the day. Precipitation will end by late Sunday evening. Thursday and Friday...Isolated afternoon and evening thunderstorms mainly over the north. .SPOTTER INFORMATION STATEMENT... Spotters are urged to report hail, wind gusts past 45 mph and any flooding. Thank you.
Special Weather Statement
National Weather Service Riverton WY
331 PM MDT SAT JUN 23 2018
WYZ007-008-017-232200-
Owl Creek and Bridger Mountains-Wind River Basin-Bighorn Mountains
West-
331 PM MDT SAT JUN 23 2018
...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN HOT SPRINGS...
NORTHWESTERN NATRONA AND NORTHEASTERN FREMONT COUNTIES UNTIL 400 PM
MDT...
At 330 PM MDT, Doppler radar was tracking a strong thunderstorm 11
miles northwest of Lysite, or 15 miles northeast of Shoshoni, moving
east at 20 mph.
Pea-sized to one-half inch diameter hail, wind gusts around 40 mph,
brief heavy rain, and dangerous lightning will be possible with this
storm.
This strong thunderstorm will be near...
Cottonwood Pass around 400 PM MDT.
LAT...LON 4326 10733 4326 10737 4329 10741 4329 10752
4328 10752 4333 10803 4348 10805 4350 10734
TIME...MOT...LOC 2130Z 263DEG 18KT 4338 10785
CNJSpecial Weather Statement
National Weather Service Riverton WY
333 PM MDT SAT JUN 23 2018
WYZ009-020-232215-
Bighorn Mountains Southeast-Natrona County Lower Elevations-
333 PM MDT SAT JUN 23 2018
...SIGNIFICANT WEATHER ADVISORY FOR NORTH CENTRAL NATRONA COUNTY
UNTIL 415 PM MDT...
At 333 PM MDT, Doppler radar was tracking a strong thunderstorm 8
miles west of Red Wall, or 28 miles southwest of Kaycee, moving east
at 25 mph.
Pea to penny size hail, wind gusts around 45 mph, brief heavy rain,
and dangerous lightning will be possible with this storm.
This strong thunderstorm will be near...
Red Wall around 355 PM MDT.
Other locations impacted by this storm include Willow Creek School.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
&&
LAT...LON 4332 10711 4349 10712 4350 10684 4349 10682
4349 10668 4319 10665
TIME...MOT...LOC 2133Z 268DEG 20KT 4343 10707
CNJSpecial Weather Statement
National Weather Service Riverton WY
335 PM MDT SAT JUN 23 2018
WYZ020-232215-
Natrona County Lower Elevations-
335 PM MDT SAT JUN 23 2018
...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN NATRONA COUNTY UNTIL
415 PM MDT...
At 334 PM MDT, Doppler radar was tracking a strong thunderstorm 7
miles southwest of Teapot Rock, or 23 miles north of Casper, moving
west at 15 mph.
Dime size hail and winds in excess of 40 mph will be possible with
this storm.
This storm will remain over mainly rural areas of northeastern
Natrona County.
This includes Interstate 25 between mile markers 199 and 223.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
To report severe weather, contact your nearest law enforcement
agency. They will relay your report to the National Weather Service
office in Riverton.
&&
LAT...LON 4297 10609 4303 10658 4329 10661 4346 10608
4330 10607
TIME...MOT...LOC 2134Z 082DEG 14KT 4317 10643
BakerPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE RIVERTON WY
417 PM MDT SAT JUN 23 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0415 PM HAIL MIDWEST 43.41N 106.28W
06/23/2018 E0.75 INCH NATRONA WY TRAINED SPOTTER
DIME TO PENNY SIZED HAIL COVERED THE GROUND.
&&
CJONESPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE RIVERTON WY
433 PM MDT SAT JUN 23 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0420 PM HAIL MIDWEST 43.41N 106.28W
06/23/2018 E1.00 INCH NATRONA WY TRAINED SPOTTER
NICKEL TO QUARTER SIZED HAIL FELL IN MIDWEST WITH
ACCUMULATIONS ONE INCH DEEP.
&&
CJONESSpecial Weather Statement National Weather Service Riverton WY 447 PM MDT SAT JUN 23 2018 WYZ007-017-232315- Owl Creek and Bridger Mountains-Wind River Basin- 447 PM MDT SAT JUN 23 2018 ...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN HOT SPRINGS AND NORTHEASTERN FREMONT COUNTIES UNTIL 515 PM MDT... At 446 PM MDT, Doppler radar was tracking a strong thunderstorm 13 miles east of Boysen State Park Headquarters, or 15 miles northeast of Shoshoni, moving east at 35 mph. Half inch hail and winds in excess of 30 mph will be possible with this storm. Brief heavy rain will also occur with this storm. This storm will remain over mainly rural areas of southeastern Hot Springs and northeastern Fremont Counties. PRECAUTIONARY/PREPAREDNESS ACTIONS... && LAT...LON 4332 10800 4350 10800 4354 10762 4330 10752 TIME...MOT...LOC 2246Z 268DEG 31KT 4342 10790 AR
The Riverton/Lander radar (KRIW), 182 km away, was scanning. The volume nearest the first event began at 23:10 UTC.
1 flash flood, 1 hail. Local standard time, as filed.
Trained spotters reported flash flooding on Fitzhugh and Lewis streets. Videos were posted on social media of the flooding as well.
Hail up to quarter size fell in Midwest. There was a large amount of small hail as well that caused localized flooding. The hail flowed into a wash and piled up several feet in places.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2018Every state in 2018This day in weather historyWarnings in Wyoming, June 2018
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: 757069, 757068.