Thunderstorms developed over portions of central Wyoming and brought strong winds. The strongest gust was 78 mph along Interstate 80 in eastern Sweetwater County.
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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.
Thunderstorms developed over portions of central Wyoming and brought strong winds. The strongest gust was 78 mph along Interstate 80 in eastern Sweetwater County. A 61 mph gust was reported in Thermopolis.
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 Aug 10, 10:49 AM MST, 1 hour 46 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 1149 AM MDT Sat Aug 10 2019 .SHORT TERM...Today and tonight Northwest-oriented ridge axis remains over the Cowboy State today. An upper low associated with a longwave trough just off the West Coast, is beginning to make its way onshore this morning. This low will slowly make its way over northern CA today and finally begin to fill later this evening. Shortwaves further south over UT will make their way over the western half of the forecast area this afternoon. Apart from high clouds streaming over the area this morning, skies are mostly clear. This will allow for differential heating to initiate convection shortly after 18Z. Storm coverage will begin along and west of a Cody to Rock Springs line through 21Z. Thunderstorms will then encompass much of the forecast area, except the far west, as storms move to the northeast. By 00Z Sunday, storms will be along and east of an Alpine to Buffalo line. Moisture remains readily available across the area, with Gulf moisture confined to eastern WY. Locally heavy rain and gusty winds will be possible with thunderstorms this afternoon and evening. Stronger storms will be possible across the north, due to the increased shear profiles with southeast sfc winds and higher dewpoints. Storms will quickly end this evening from southwest to northeast, lasting over Johnson County through 06Z. Low clouds will be possible once again over Natrona County and southern Johnson County by the predawn hours Sunday morning. .LONG TERM...Sunday through Saturday A cold front will push through the area Sunday, lowering humidities and bringing breezy to gusty winds across the region. Temperatures will not drop much and a Fire Weather Watch has been issued for central areas due to the expected combination of low RH, warm temps, and gusty winds. After Sunday, zonal flow that slowly transitions into a weak ridge will keep drier weather in the forecast through most of the week. Relative humidities in the afternoons will be characteristically low for this time of year with teen values expected in central and southern Wyoming. Monday will also need to be watched as gusty winds return and along with the low RH and warm temps will likely elevate fire weather conditions again. By Thursday and Friday the pattern begins to change as an upper trough moves from the west coast eastward into Montana. As this change begins to take place the northern mountains start to see some precipitation in the afternoons again. Also with the trough, models are indication a surface cold front will begin to move into the area by Friday afternoon. Though subject to change this far out, the front looks to be weak and may stall out over the state. Temperatures will be around normal through the period. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) Expect isolated to scattered afternoon and evening thunderstorms mainly along and east of the Divide. Will continue to have mention of VCTS in the tafs east of the Divide, and will also continue to watch potential for VCTS at KRKS. Will continue with thinking of lessening chances of SHRA/TSRA after 03Z tonight. VFR conditions will continue through the forecast period, with the exception of brief IFR/MVFR conditions in convection. && .FIRE WEATHER... ...Fire Weather Watch in effect from Sunday afternoon and evening for zones 280, 283 and 288... Scattered thunderstorms will occur across the area this afternoon. Some storms across the north could be strong. This activity will end from southwest to northeast this evening, with storms lasting through midnight over Johnson County. A cold front will move across the area Sunday, ushering in drier air and gusty winds in its wake. Thus, a Fire Weather Watch remains in effect for central zones for Sunday afternoon and evening. Thunderstorms, some of which could be strong, will be possible over zones 280 and 281 late Sunday afternoon. However, most of this activity is expected further east out of the forecast area. && .RIW WATCHES/WARNINGS/ADVISORIES... Fire Weather Watch from Sunday afternoon through Sunday evening for WYZ280-283-288. && SHORT TERM...LaVoie LONG TERM...Bourque AVIATION...Troutman FIRE WEATHER...LaVoie
Hazardous Weather Outlook National Weather Service Riverton WY 242 AM MDT Sat Aug 10 2019 WYZ001>020-022>030-110845- 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- 242 AM MDT Sat Aug 10 2019 ...Fire Weather Watch for portions of central Wyoming Sunday Afternoon and Evening... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight Scattered afternoon and evening thunderstorms. Strong storms will be possible over northern portions. .DAYS TWO THROUGH SEVEN...Sunday through Friday. Sunday...Elevated to critical fire weather conditions over central and southern areas. Isolated to scattered afternoon and early evening thunderstorms over eastern portions. Some thunderstorms could be strong to possibly severe mainly over Johnson County. Monday through Thursday...Elevated to near-critical fire conditions over central and southern portions. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report significant weather conditions according to standard operating procedures.
Special Weather Statement
National Weather Service Riverton WY
1234 PM MDT Sat Aug 10 2019
WYZ011-101900-
Southeast Johnson County-
1234 PM MDT Sat Aug 10 2019
...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN JOHNSON COUNTY UNTIL
100 PM MDT...
At 1232 PM MDT, Doppler radar was tracking a strong thunderstorm near
Hole In The Wall, which is 11 miles southwest of Kaycee, moving
northeast at 15 mph.
Half inch hail and winds in excess of 30 mph will be possible with
this storm. Spotter has reported half inch hail in the vicinity of
Barnum.
This strong thunderstorm will be near...
Kaycee around 100 PM MDT.
This includes Interstate 25 between mile markers 247 and 265.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Heavy rainfall is also occurring with this storm, and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.
&&
LAT...LON 4355 10680 4371 10693 4372 10691 4370 10688
4372 10687 4374 10688 4374 10687 4371 10683
4375 10683 4376 10684 4376 10682 4377 10682
4401 10637 4378 10618
TIME...MOT...LOC 1832Z 241DEG 15KT 4364 10685
SwansonPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE RIVERTON WY
1235 PM MDT SAT AUG 10 2019
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1226 PM HAIL 1 SW BARNUM 43.65N 106.93W
08/10/2019 M0.50 INCH JOHNSON WY TRAINED SPOTTER
ALSO HAD 1/4 INCH OF RAIN IN 45 MINUTES WITH THE STORM
&&
GSWANSONSpecial Weather Statement
National Weather Service Riverton WY
122 PM MDT Sat Aug 10 2019
WYZ030-101945-
East Sweetwater County-
122 PM MDT Sat Aug 10 2019
...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL SWEETWATER COUNTY UNTIL
145 PM MDT...
At 120 PM MDT, Doppler radar was tracking a strong thunderstorm near
Bitter Creek Rest Area, which is 28 miles west of Wamsutter, moving
northeast at 30 mph.
Winds of 40 to 50 mph will be possible with this storm.
This strong thunderstorm will be near...
Bitter Creek Rest Area around 125 PM MDT.
Other locations impacted by this storm include Bitter Creek, Tipton,
Red Desert and Point Of Rocks.
This includes Interstate 80 between mile markers 128 and 172.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Occasional 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 4151 10892 4199 10871 4200 10870 4202 10864
4203 10863 4205 10865 4206 10864 4207 10864
4209 10859 4182 10783 4128 10844
TIME...MOT...LOC 1920Z 217DEG 34KT 4157 10852
HulmeThe Riverton/Lander radar (KRIW), 158 km away, was scanning. The volume nearest the first event began at 19:34 UTC.
2 thunderstorm wind. Local standard time, as filed.
Several wind gusts over 58 mph were recorded at Bitter Creek along Interstate 80. The highest recorded gust was 78 mph.
An outflow boundary moved through Thermopolis, Wyoming and brought a 61 mph wind gust to the fire station just south of downtown Thermopolis.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2019Every state in 2019This day in weather historyWarnings in Wyoming, August 2019
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: 836170, 836171.