Heavy rain caused a debris flow off the Bear Burn Scar.
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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.
Heavy rain caused a debris flow off the Bear Burn Scar.
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 Aug 22, 2:38 PM MST, 4 hours 2 minutes earlier.
Area Forecast Discussion National Weather Service Salt Lake City UT 338 PM MDT Tue Aug 22 2023 .SYNOPSIS...Deep moisture and heightened instability will bring a threat of showers and thunderstorms, some severe, capable of producing flash flooding through this evening. Northern Utah will see slight drying Wednesday, with monsoonal moisture potentially combining with the remnants of Tropical Storm Harold to increase the flash flood threat Thursday into Friday. Drier air is expected to move in this weekend. && .DISCUSSION...Southerly flow persists over Utah and southwest Wyoming this afternoon in between high pressure over the central United States and a California trough moving into the Great Basin. Moisture, as has been the case for the past several days, remains quite elevated with widespread satellite derived PW values in excess of 1.0 inch over central and southern Utah with values closer to 0.8 inch over northern Utah and southwest Wyoming. The trough to the west is accompanied by a strong jet, increasing instability over the area, especially western Utah. Showers have stretched from northwest Utah all the way down through western Arizona into Mexico, and this has kept cloud cover in place. However, satellite imagery indicates this cloud cover is eroding, and areas on the east end of this persistent cloud cover have seen strong to severe convection. CAMs continue to indicate the development of supercells in this area, and though they have been showing a tendency to overdo the convection lately, think the potential for severe winds from storms exists through the early evening. Seeing the erosion of cloud cover further south which should allow for additional convective development down there, which will increase the threat of flash flooding through the early evening. Going Flood Watch for southern Utah covers this threat well. The California trough will continue to weaken and lift northward over the ridge tonight, decreasing instability over the area for Wednesday. Also, with the flow becoming more southwesterly over northern Utah, some drying is anticipated. Guidance indicates PWs in that area dropping to as low as 0.6 inch during the day Wednesday, which would help to suppress the convective threat a bit. Meanwhile, southern Utah will hold onto PWs around 1.0 inch, so should continue to see good coverage of storms accompanied by heavy rainfall. The drying trend over northern Utah will be short lived, however. A Pacific Northwest trough is expected to slide across Washington and northern Idaho late Wednesday before entering Canada Wednesday night, shifting the flow to a more straight southerly direction. As this happens, the remnants of Tropical Storm Harold (which just made landfall in Texas) will get entangled in our southerly flow and lift northward. Still seeing a bit of spread as to where these remnants go, but eastern Utah or western Colorado are looking increasingly likely as landing spots, with Thursday evening into Friday looking like the most likely time for passage. Given just how much available moisture we have had over the past couple of weeks, the flooding threat will not change much, but given the potential of evening/overnight timing, this will bring the potential for more organized precip into the overnight hours as well. For those sick of all the moisture, we're seeing hope for drier conditions over the weekend. As what's left of Harold passes to the north of the area by late Friday, high pressure is expected to rebuild back west, potentially putting Utah and southwest Wyoming under a more westerly flow aloft, with confidence increasing that this will draw some drier air back in from the west over the weekend. While the deeper moisture may not entirely go away, particularly near the Utah/Arizona border, it should decrease some, thus decreasing coverage of showers and thunderstorms. Uncertainty increases as we move into next week, with some guidance moving high pressure overhead and some allowing it to shift a bit east, allowing some moisture to move back in. && .AVIATION...KSLC...There's a small (20%) chance for a thunderstorm in the vicinity of KSLC before 00z. Otherwise, nearby scattered showers will continue through roughly 04-05z. Brief periods of MVFR VIS/CIGs are possible, along with the occasional gust near 20kts. Expect light, southeasterly flow overnight. .REST OF UTAH AND SOUTHWEST WYOMING...Scattered showers will continue across much of the area until roughly 08-09z, with isolated thunderstorms possible mainly east of I-15. These thunderstorms will be capable of producing gusty and erratic outflow winds. A few rain showers may develop around 12z across south-central Utah, including KBCE. With clearing skies near KENV overnight, there's a small (20%) chance of low clouds developing around 1000ft between 10-14z, but this is unlikely to be impactful. Otherwise, expect largely light, diurnally-driven winds and VFR conditions. && .FIRE WEATHER...Deep subtropical moisture remains in place over Utah this afternoon. Some modest drying is expected Wednesday, primarily for northern Utah, but the drying will be short lived. For Thursday into Friday, monsoonal moisture will return northward, perhaps accompanied by the remnants of Tropical Storm Harold, allowing coverage of showers and thunderstorms, and thus the threat of heavy rain capable of producing flash flooding, to increase. Behind the wave, building high pressure will bring a more westerly direction to the flow aloft, allowing for a drying trend over the weekend. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...Flood Watch until midnight MDT tonight for UTZ122>129-131. WY...None. && Traphagan/Cunningham For more information from NOAA's National Weather Service visit... http://weather.gov/saltlakecity
Special Weather Statement
National Weather Service Salt Lake City UT
427 PM MDT Tue Aug 22 2023
UTZ128-131-222300-
South Central Utah UT-Glen Canyon Recreation Area/Lake Powell UT-
427 PM MDT Tue Aug 22 2023
...A strong thunderstorm will impact portions of south central San
Juan and east central Kane Counties through 500 PM MDT...
At 427 PM MDT, Doppler radar was tracking a strong thunderstorm 9
miles north of Rainbow Bridge South Trailhead, or 34 miles northeast
of Page, moving northwest at 20 mph.
HAZARD...Wind gusts up to 50 mph and half inch 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...
Lake Powell.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.
&&
LAT...LON 3713 11075 3707 11089 3716 11118 3736 11092
TIME...MOT...LOC 2227Z 138DEG 16KT 3713 11089
MAX HAIL SIZE...0.50 IN
MAX WIND GUST...50 MPH
STWSpecial Weather Statement
National Weather Service Salt Lake City UT
506 PM MDT Tue Aug 22 2023
UTZ128>131-222330-
Capitol Reef National Park and Vicinity UT-South Central Utah UT-
Western Canyonlands UT-Glen Canyon Recreation Area/Lake Powell UT-
506 PM MDT Tue Aug 22 2023
...A strong thunderstorm will impact portions of south central
Garfield and northeastern Kane Counties through 530 PM MDT...
At 506 PM MDT, Doppler radar was tracking a strong thunderstorm 15
miles southwest of Glen Canyon National Recreation Area, or 40 miles
southeast of Escalante, moving north at 25 mph.
HAZARD...Wind gusts up to 50 mph and penny 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...
Glen Canyon National Recreation Area.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.
&&
LAT...LON 3734 11088 3729 11106 3754 11129 3767 11109
3769 11090
TIME...MOT...LOC 2306Z 167DEG 23KT 3740 11103
MAX HAIL SIZE...0.75 IN
MAX WIND GUST...50 MPH
STWSpecial Weather Statement
National Weather Service Salt Lake City UT
530 PM MDT Tue Aug 22 2023
UTZ128>130-230000-
Capitol Reef National Park and Vicinity UT-South Central Utah UT-
Western Canyonlands UT-
530 PM MDT Tue Aug 22 2023
...A strong thunderstorm will impact portions of south central
Garfield and northern Kane Counties through 600 PM MDT...
At 530 PM MDT, Doppler radar was tracking a strong thunderstorm 16
miles west of Glen Canyon National Recreation Area, or 31 miles east
of Escalante, moving north at 25 mph.
HAZARD...Wind gusts up to 50 mph and nickel 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...
Glen Canyon National Recreation Area.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.
&&
LAT...LON 3752 11093 3749 11115 3782 11130 3790 11111
3791 11093
TIME...MOT...LOC 2330Z 170DEG 23KT 3760 11106
MAX HAIL SIZE...0.88 IN
MAX WIND GUST...50 MPH
STWSpecial Weather Statement
National Weather Service Salt Lake City UT
543 PM MDT Tue Aug 22 2023
UTZ123-230015-
Lower Washington County UT-
543 PM MDT Tue Aug 22 2023
...A strong thunderstorm will impact portions of south central
Washington County through 615 PM MDT...
At 543 PM MDT, Doppler radar was tracking a strong thunderstorm 7
miles southeast of St George, or 20 miles east of Virgin River Gorge,
moving north at 15 mph.
HAZARD...Wind gusts up to 50 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
Locations impacted include...
St George, Washington, Hurricane, La Verkin, Sand Hollow State Park,
Quail Creek State Park and Virgin.
This includes Interstate 15 between mile markers 10 and 20.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.
&&
LAT...LON 3700 11356 3720 11353 3721 11351 3720 11324
3700 11339
TIME...MOT...LOC 2343Z 196DEG 13KT 3703 11346
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPH
STWSpecial Weather Statement
National Weather Service Salt Lake City UT
615 PM MDT Tue Aug 22 2023
UTZ125-128>130-230045-
Capitol Reef National Park and Vicinity UT-South Central Utah UT-
Western Canyonlands UT-Southern Mountains UT-
615 PM MDT Tue Aug 22 2023
...A strong thunderstorm will impact portions of north central
Garfield and southwestern Wayne Counties through 645 PM MDT...
At 615 PM MDT, Doppler radar was tracking a strong thunderstorm 19
miles south of Capitol Reef National Park, moving north at 25 mph.
HAZARD...Wind gusts up to 50 mph and half inch 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...
Capitol Reef National Park.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.
&&
LAT...LON 3784 11093 3784 11116 3816 11121 3821 11106
3816 11088
TIME...MOT...LOC 0015Z 179DEG 21KT 3791 11105
MAX HAIL SIZE...0.50 IN
MAX WIND GUST...50 MPH
STWSpecial Weather Statement
National Weather Service Salt Lake City UT
643 PM MDT Tue Aug 22 2023
UTZ122>125-230115-
Southwest Utah UT-Southern Mountains UT-Zion National Park UT-
Lower Washington County UT-
643 PM MDT Tue Aug 22 2023
...A strong thunderstorm will impact portions of northeastern
Washington...northwestern Kane and south central Iron Counties
through 715 PM MDT...
At 643 PM MDT, Doppler radar was tracking a strong thunderstorm 7
miles southeast of New Harmony, or 12 miles northwest of Zion
National Park, moving northeast at 30 mph.
HAZARD...Wind gusts up to 50 mph and penny 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...
Cedar City, Zion National Park, Cedar Breaks National Monument,
Kanarraville, Hamilton Fort and Kolob Canyon.
This includes the following highways...
Interstate 15 between mile markers 35 and 61.
Utah Route 56 between mile markers 56 and 61.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.
This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.
&&
LAT...LON 3732 11318 3742 11332 3774 11313 3770 11298
3757 11279
TIME...MOT...LOC 0043Z 214DEG 25KT 3743 11318
MAX HAIL SIZE...0.75 IN
MAX WIND GUST...50 MPH
STWThe Salt Lake City radar (KMTX), 208 km away, was scanning. The volume nearest the first event began at 01:37 UTC.
1 debris flow, 1 thunderstorm wind. Local standard time, as filed.
Heavy rain resulted in a debris flow at the Bear Burn Scar. The flow remained internal to the scar and did not cross US-6, although there were a few softball-sized rocks that made it onto the roadway.
Mesonet station UTDOL Dolomite recorded a wind gust of 61 mph.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Utah in 2023Every state in 2023This day in weather historyWarnings in Utah, 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: 1189218, 1189615.