Isolated convection developed during the afternoon hours, with a lone supercell thunderstorm producing flash flooding in slot canyons across Goblin Valley, while other thunderstorms produced wind damage over northern Utah.
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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 SLC wrote it up.
Isolated convection developed during the afternoon hours, with a lone supercell thunderstorm producing flash flooding in slot canyons across Goblin Valley, while other thunderstorms produced wind damage over northern Utah.
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 Salt Lake City, UT wrote its last area forecast discussion before the first event at May 11, 9:38 AM MST, 3 hours 7 minutes earlier.
Area Forecast Discussion National Weather Service Salt Lake City UT 1038 AM MDT Mon May 11 2020 .SYNOPSIS... A couple of weak weather systems will cross the forecast area through Wednesday. Mild conditions will remain in place through Tuesday, before somewhat cooler weather with a chance of showers arrives midweek. && .SHORT TERM (Through 12Z Thursday)... A weak upper level disturbance will push the mid-high level moisture over mainly eastern Utah by this afternoon for a chance of mainly high-based showers and thunderstorms. However, instability caused by heating of the mountains will allow for a slight chance of high-based showers and thunderstorms to remain over the central and northern mountains into this afternoon. Gusty winds in excess of 30 mph are possible with any of these storms. Otherwise, subsidence and a general clearing trend in the wake of the shorwave passage will help mix gusty winds to the surface across western UT, especially SW Utah including the I-15 corridor near Cedar City, where gusts 30 to 40 mph are possible this afternoon. The excellent mixing and subsidence in an unmodifed airmass wil also result in another day of warm temperatures running about 15 degrees above seasonal average. Another disturbance will brings its associated dry cold front into northwest Utah this evening and into central Utah by Tuesday afternoon. Warm and breezy conditions will prevail ahead of this front, while temperatures will fall by 6-10 degrees behind this front across the north. A secondary and slightly stronger cold front will bring a threat of showers to northern Utah and the central mountains Wednesday, while the rest of the southern half of Utah should remain dry. Temperatures will fall below normal across the north Wednesday and be near normal across the south. .LONG TERM (After 12Z Thursday)... A mostly zonal flow pattern will continue into the later half of the week with an upstream trough in the PacNW. A weak shortwave will linger across northern Utah Thursday and Friday resulting in afternoon convective rain showers and isolated thunderstorms. A mainly dry boundary layer and lack of deep moisture will likely keep any rainfall to a minimum and keep the hazards to gusty winds. Daytime temperatures will be near or just below seasonal normal (perhaps on the cool side if you want to describe it that way). Heading into the following weekend, a short ridge will allow southwest flow aloft to advect in warmer temperatures aloft and warm daytime temps 5+ degrees above seasonal normals. Saturday and Sunday look to be on the dry side with perhaps chances for mountain showers and thunderstorms focused in northern Utah. Extended range ensemble guidance begins to hint at a deepening low off the West Coast by early next week among all model solutions. We'll have to see how that plays out. && .AVIATION...Gusty south winds will prevail at the KSLC terminal through the afternoon, with periods likely seeing gusts greater than 26 kts. Ceilings around 8k to 9k feet are expected. A period of gusty westerly winds is possible this evening with little chance of a shift to the northwest. && .FIRE WEATHER...A disturbance aloft will continue the threat of high-based showers and thunderstorms over the mountains and eastern portions of the fire district today while slightly drier air moves into western Utah. A secondary and slightly stronger disturbance will push a cold front into northwest Utah late tonight and into central Utah Tuesday afternoon. Temperatures will fall about 6-10 degrees behind the front while warm and breezy conditions continue south of the cold front. A reinforcing cold front will push into northern Utah Tuesday night and then sweep through the remainder of Utah Wednesday. There will be a chance of showers associated with this front across northern Utah and the central mountains, but the rest of the southern half the state should remain dry. Temperatures will fall below normal across the north and be near normal across the south Wednesday through Friday. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...None. WY...None. && SHORT TERM...Struthwolf/Church LONG TERM...Dewey AVIATION...Dewey FIRE WEATHER...Struthwolf For more information from NOAA's National Weather Service visit... http://weather.gov/saltlakecity For frequently asked questions about the Area Forecast Discussion visit... http://weather.gov/saltlakecity/general/afd_faqs.php
Hazardous Weather Outlook National Weather Service Salt Lake City UT 756 AM MDT Mon May 11 2020 UTZ001>016-019>021-517-518-WYZ021-121400- Cache Valley/Utah Portion-Northern Wasatch Front- Salt Lake and Tooele Valleys-Southern Wasatch Front- Great Salt Lake Desert and Mountains-Wasatch Mountain Valleys- Wasatch Mountains I-80 North-Wasatch Mountains South of I-80- Western Uinta Mountains-Wasatch Plateau/Book Cliffs- Western Uinta Basin-Castle Country-San Rafael Swell- Sanpete/Sevier Valleys-West Central Utah-Southwest Utah- Utahs Dixie and Zion National Park-South Central Utah- Glen Canyon Recreation Area/Lake Powell-Central Mountains- Southern Mountains-Southwest Wyoming- 756 AM MDT Mon May 11 2020 This Hazardous Weather Outlook is for the western two thirds of Utah and southwest Wyoming. .DAY ONE...Today and Tonight No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed. Please relay any information about observed severe weather to the NWS while following all local, state, and CDC guidelines. Spotter activation will not be needed. For more information from NOAA/s National Weather Service visit... http://weather.gov/saltlakecity For information on potential road travel impacts visit... http://www.udottraffic.utah.gov/roadweatherforecast.aspx
Special Weather Statement
National Weather Service Salt Lake City UT
1205 PM MDT Mon May 11 2020
UTZ009-011-111845-
Western Uinta Basin UT-Western Uinta Mountains UT-
1205 PM MDT Mon May 11 2020
...SIGNIFICANT WEATHER ADVISORY FOR EAST CENTRAL DUCHESNE COUNTY
UNTIL 1245 PM MDT...
At 1203 PM MDT, National Weather Service Doppler radar indicated a
strong thunderstorm 11 miles west of Whiterocks...moving east at 20
mph.
Half inch hail and winds 40 to 50 mph are possible.
Locations impacted include...
Roosevelt, Myton, Altamont, Upalco, Neola, Altonah and Cedarview.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If threatening weather approaches, take shelter in a sturdy building.
&&
LAT...LON 4035 11036 4052 11023 4052 10998 4014 10998
4014 10999
TIME...MOT...LOC 1803Z 279DEG 17KT 4043 11016
ChurchSpecial Weather Statement
National Weather Service Salt Lake City UT
1244 PM MDT Mon May 11 2020
UTZ010-011-111930-
Wasatch Plateau/Book Cliffs UT-Western Uinta Basin UT-
1244 PM MDT Mon May 11 2020
...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN DUCHESNE COUNTY
UNTIL 130 PM MDT...
At 1243 PM MDT, National Weather Service Doppler radar indicated
strong thunderstorms along a line extending from 12 miles northwest
of Roosevelt to 7 miles east of Duchesne...and moving east at 20 mph.
Half inch hail and wind gusts up to 50 mph are possible.
Locations impacted include...
Roosevelt, Duchesne, Myton, Starvation Reservoir, Altamont, Upalco,
Arcadia, Altonah, Cedarview, Bridgeland and Neola.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If threatening weather approaches, take shelter in a sturdy building.
&&
LAT...LON 4012 11049 4046 11027 4042 10998 4006 10997
3991 10998
TIME...MOT...LOC 1843Z 290DEG 17KT 4037 11021 4014 11025
ChurchSpecial Weather Statement National Weather Service Salt Lake City UT 105 PM MDT Mon May 11 2020 UTZ013-112000- San Rafael Swell UT- 105 PM MDT Mon May 11 2020 ...SIGNIFICANT WEATHER ADVISORY FOR NORTH CENTRAL WAYNE AND SOUTH CENTRAL EMERY COUNTIES UNTIL 200 PM MDT... At 104 PM MDT, National Weather Service Doppler radar indicated a strong thunderstorm 15 miles northwest of Hanksville...moving east at 20 mph toward Goblin Valley. Half inch hail and wind gusts up to 50 mph will be possible. Locations impacted include... Goblin Valley. PRECAUTIONARY/PREPAREDNESS ACTIONS... If threatening weather approaches, take shelter in a sturdy building. && LAT...LON 3843 11100 3861 11102 3876 11050 3839 11044 TIME...MOT...LOC 1904Z 263DEG 19KT 3854 11091 Church
The Cedar City radar (KICX), 211 km away, was scanning. The volume nearest the first event began at 19:43 UTC.
2 thunderstorm wind, 1 flash flood. Local standard time, as filed.
Flash flooding occurred in Little Wild Horse, Bell, Crack, and Dang Canyons, with two confirmed fatalities.
Damaging thunderstorm wind gusts downed large tree branches in the Salt Lake Valley.
Damaging thunderstorm wind gusts downed a tree in Davis County.
As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.
| Event | Date | Age | Sex | Where | Kind |
|---|---|---|---|---|---|
| Flash Flood, Emery | 2020-05-11 | 3 | Female | In Water | Direct |
| Flash Flood, Emery | 2020-05-11 | 7 | Female | In Water | Direct |
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Utah in 2020Every state in 2020This day in weather historyWarnings in Utah, May 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: 892502, 892503, 892504.