Several places around Zion National Park had flooding as monsoonal showers and thunderstorm tracked there.
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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.
Several places around Zion National Park had flooding as monsoonal showers and thunderstorm tracked there.
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 14, 3:32 AM MST, 10 hours 14 minutes earlier.
Area Forecast Discussion National Weather Service Salt Lake City UT 432 AM MDT Mon Aug 14 2023 .SYNOPSIS...Moisture remains in place across southern Utah today while drier air has spread into the north, remaining there through the early part of the week. This will limit precipitation chances across the north through the first half of the week while isolated to scattered precipitation chances continue across southern Utah. More significant moisture may spread into the area late week and through the weekend. && .SHORT TERM (THROUGH 12Z THURSDAY)...The large-scale pattern this morning continues to depict a Rex Block over the West Coast consisting of a high over WA/OR and closed low off the SoCal Coast. Downstream, an upper low continues to move into the Midwest. In between these features, there is Utah. As the downstream low continues to shift east today, the Rex Block will weaken as the high pressure spills eastward and heights rise over Utah. Drier air remains in place across the north where PWATs are in the 0.5-0.6 inch range, while southern Utah remains more moist with PWATs between 0.7-0.9 inches. Showers with isolated embedded thunderstorms have been noted all night across southern Utah, this as moisture continues to be advected into the area from the southeast and focusing near the southern (moist) side of a deformation/shear axis. Meanwhile, an easterly surface pressure gradient has developed across northern Utah and southwest Wyoming in response to cooler air and higher pressure over the Great Plains in the wake of the Midwest low. This is driving easterly canyon winds along the northern through central Wasatch Front and Cache Valley. The strongest gust noted thus far has been 52 mph near Farmington, otherwise most areas near canyons have been seeing 30-45 mph gusts. This gradient should weaken by mid-morning, allowing winds to decrease thereafter. By afternoon, the low over the SoCal coast will retrograde a bit to the northwest. This will bring more of a southerly flow to Utah. Expect showers to develop again over the higher terrain of southern and central Utah with storms tracking to the northwest. Locally heavy rainfall will once again be a threat across southern Utah, while central Utah storms may be a bit drier and have a greater threat of gusty outflow winds. However, due to morning precipitation, the airmass may not be supportive of strong afternoon convection, and CAMs are supportive of this idea and HREF ensemble mean SBCAPE reflects this with modest values of generally 250J/kg or less. High pressure will gradually strengthen over the intermountain region tomorrow. The moisture will have spread a bit farther into northern Utah tomorrow, and the result will be a few diurnal showers over the northern mountains. Otherwise, temperatures will in general trend warmer across the area today through tomorrow. .LONG TERM (After 12Z Tuesday)...The pattern will be shifting as the long term period progresses. To start, a ridge centered over the four corners will keep diurnal convection across southern Utah with near seasonal temperatures Wednesday and Thursday. Northern Utah and SW Wyoming will remain dry with temperatures 5-7 degrees above normal with the hottest day being Thursday. The forecast high for KSLC on Thursday is 99 degrees with a 10% of reaching 100. Cloud cover migrating in from the south could be the determining factor of how hot it gets across northern Utah on Thursday. Moisture becomes plentiful across the entire region by the end of the week and through the weekend as a cutoff low off the coast of California progresses further east and the aforementioned ridge slides east leading to a moist southerly flow. Ensemble mean PWATs >1" for late Thursday/Friday will spread throughout the CWA. This is above the 90th percentile for KSLC for the date. Synoptic forcing will still be relatively weak so the greatest precipitation chances will remain across the higher terrain. Temperatures, however, will moderate back to near seasonal values given the increased cloud cover and the shift of the ridge axis. As we head into the weekend the cutoff low will start to phase back in with the mean flow as a deep trough develops across the western CONUS. This trough will provide enhanced synoptic lift resulting in more widespread precipitation chances areawide. A tropical disturbance currently south of Guatemala has a 90% chance of developing into a cyclone within the next 7 days. The trajectory of this potential tropical cyclone will be closely monitored as 47% of guidance (mainly the GEFS and CAN) are tracking it adjacent to the Baja of California which would send a long lasting plume of very moist air into the Great Basin/Desert SW. This, in tandem with the western CONUS trough, would greatly increase the flash flood threat across the region. Currently most EC guidance is not on board with this solution. The deterministic EC has this cyclone taking a more westerly track which would keep the deepest moisture well offshore. && .AVIATION...KSLC...VFR conditions will prevail throughout the period for the KSLC terminal. Light easterly winds will transition to light southerly drainage early morning. A northerly lake breeze sets up this afternoon with mostly clear skies. .REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions will prevail throughout the period for all terminals except for brief category reductions across southern Utah due to isolated afternoon convection. Gusty easterly winds across northern Utah/SW Wyoming will weaken throughout the morning before becoming more typical diurnal wind patterns. && .FIRE WEATHER...Another dry day is in store for northern Utah today while moisture remains in place across the south. Isolated to scattered mostly wet thunderstorms are expected once again today across southern Utah, with good daytime humidities and overnight recoveries. The moisture is then expected to creep slowly northward through midweek before potentially increasing more significantly by late week. While there remains much uncertainty at this time, there is a chance for widespread very significant rainfall towards the end of the week and into early next week. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...None. WY...None. && Cheng/Mahan For more information from NOAA's National Weather Service visit... http://weather.gov/saltlakecity
The Cedar City radar (KICX), 43 km away, was scanning. The volume nearest the first event began at 20:46 UTC.
2 flash flood. Local standard time, as filed.
Zion National Park reported multiple waterfalls through southern portion of the park, the biggest of which was noted near Twin Brothers.
The North Fork of the Virgin River at Springdale river gage reported a flood wave of 883 cfs. This was an increase from 64 cfs the previous hour. Additionally, Zion NP staff reported several waterfalls.
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: 1189196, 1189201.