Monsoonal flash flooding brought a variety of impacts to southern Utah, including flash flooding in Capitol Reef National Park that prompted evacuation of a campground and road closures.
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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.
Monsoonal flash flooding brought a variety of impacts to southern Utah, including flash flooding in Capitol Reef National Park that prompted evacuation of a campground and road closures.
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 17, 3:22 AM MST, 10 hours 3 minutes earlier.
Area Forecast Discussion National Weather Service Salt Lake City UT 422 AM MDT Thu Aug 17 2023 .SYNOPSIS...Monsoonal moisture will remain in place across the region, bringing daily chances for showers and thunderstorms across the area. A moisture surge from Tropical Storm Hilary is slated to move across the Great Basin region and may bring significant impacts to the forecast area late in the weekend/ early next week, but there are still some forecast challenges to work through in that regard. && .SHORT TERM (Through 12Z/6AM Saturday)...The eastern Great Basin region remains sandwiched between two large scale synoptic drivers; an offshore low near California and a developing high over the central Rocky Mountains. Deep atmospheric moisture is noted between these two features and will continue to drive diurnally driven showers and thunderstorms across the forecast area. High terrain and adjacent valley areas from roughly Zion NP north-northeastward through Uinta Co., Wyoming will see the greatest chances for seeing any sort of significant precipitation with scattered storms, whereas areas in eastern and northwestern Utah will see more isolated storms. Storm motions are expected to be relatively slow (10-20kts) and on a SW-NE trajectory. For areas sensitive to heavy rainfall (i.e. slickrock areas, dry washes, slot canyons, and recent burn scars), the threat of flash flooding will be elevated... especially for areas like Capitol Reef NP, Grand Staircase-Escalante NRA, and the various large burn scars of central and northern Utah. Temperatures will remain near seasonal today, however, any passing showers will bring potential to drop temperatures 10-15 degrees cooler than forecast. Moisture will remain spread across the region through the end of the week, and into the weekend, keeping chances for showers and thunderstorms in the forecast for Friday. The caveat here is that Friday will feature a bit more support from the offshore low, which will increase the overall coverage of storms, especially across the southern half of the forecast area. The risk of flash flooding will remain elevated on Friday and spread a little further north into northern Utah, where areas featuring steep, rocky terrain or recently burned areas will see an increased threat. .LONG TERM (After 12Z/6AM Saturday)...A complex pattern will be in place to start the long term period. A ridge over the central CONUS and a cutoff low off the coast of California will keep a moist southerly flow advecting into the entire CWA. This will help to develop afternoon convection on Saturday with the highest probabilities across southern Utah. In addition to the typical monsoonal moisture plume, tropical storm Hilary will be moving up the Baja of California coast with impacts to portions of the desert SW Sunday through Tuesday. The highest confidence track currently keeps a bulk of this tropical moisture across California and Nevada. However, any deviations further east would result in a greater flash flood potential to Utah and SW Wyoming. A further track west/east would also result in temperatures near normal/below normal. Currently there is a marginal risk of flash flooding across Utah Saturday and Sunday, according to WPC's excessive rainfall outlook. Once the remnants of this tropical cyclone passes by to the north Tuesday the focus returns to a more typical monsoonal moisture plume that will be moving in from the south/southeast as the aforementioned ridge remains in place across the center of the country. This southeasterly flow will be drawing moisture up from the Gulf of Mexico as tropical moisture will be moving into northern Mexico/southern Texas. This moisture will remain in place through the end of the period as ensemble mean PWATs across northern Utah remain ~1" with near 1.15" PWATs across southern Utah. Expect temperatures to remain near normal, if not slightly below normal. && .AVIATION...KSLC...Mostly VFR conditions will prevail for the KSLC terminal through the remainder of the period. Monsoonal moisture will result in isolated afternoon convection that could briefly reduce flight categories. Gusty and variable outflow winds could result from any nearby convection. Otherwise, winds will likely remain southerly for most of the day with only a brief window of northerly lake breeze winds in the afternoon. .REST OF UTAH AND SOUTHWEST WYOMING...Mostly VFR conditions will prevail for most terminals as a monsoonal plume moving through the entire region will result in afternoon convection that could create brief flight category reductions. Additionally, winds will primarily be out of the south with gusty variable winds associated with any nearby convection. Convection over the terrain could lead to brief mountain obscuration. && .FIRE WEATHER...Deep atmospheric moisture will spread across a large majority of the region today, bringing increased risk of showers and thunderstorms across Utah. Storms will be diurnally driven and will favor higher terrain areas, as well as adjacent valley areas. Due to increased atmospheric moisture content, wetting rain chances will be anywhere from 30 to 60 percent across the high terrain (excluding northwest Utah). Heavy rainfall with isolated flooding, lightning, and gusty outflow winds will be the primary threats in passing storms. Outside of storm chances, humidity will continue to be moderated across a majority of Utah with the exception of portions of northwest and eastern Utah. In these areas, humidity may drop as low as 20%. Deep layer moisture will remain in place tomorrow with coverage of showers and thunderstorms expected to increase across the southern half of Utah. CWRs will see a significant increase in the southern and central mountains, as well as the Uintas and southern Wasatch, and adjacent valley areas with minimal change expected across far northern Utah. A much more significant surge of moisture is expected to push into Utah this weekend, bringing much higher daytime humidity values, coverage of showers and thunderstorms, and increased chances for widespread wetting rains. Moisture will remain in place through at least mid-week next week, keeping the chance for daily showers and thunderstorms in the forecast. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...None. WY...None. && Webber / Mahan For more information from NOAA's National Weather Service visit... http://weather.gov/saltlakecity
The Cedar City radar (KICX), 160 km away, was scanning. The volume nearest the first event began at 20:24 UTC.
6 flash flood, 4 thunderstorm wind, 2 high wind. Local standard time, as filed.
Flash flooding caused a closure of state Route 24 due to water covering the road from mileposts 81 to 85. The flooding led to an evacuation of the Fruita Campground and Gifford House.
Zion National Park reported flash flooding at Refrigerator and Echo Canyons.
The Escalante River at Escalante gauge was at 583 cfs.
A wind gust of 69 mph was recorded by the Salt Lake City International Airport ASOS.
ASOS station KSLC at Salt Lake City International Airport recorded a wind gust of 69 mph.
Mesonet site UTRKY at Rocky Ridge recorded a wind gust of 61 mph.
Heavy rain produced flash flooding in Cedar City, impacting the Cedar City Hospital, Iron County Jail, and homes.
Mesonet station FREUT at Fremont Isoland - Miller Hill recorded a wind gust of 58 mph.
A wind gust of 65 mph was recorded in Snowville.
Mesonet station UCC01 at Snowville recorded a wind gust of 64 mph.
There were reports of flooding at a campground in Cedar Canyon. The Cedar Canyon stream gauge reported a significant rise.
There was a 798 cfs rise on the East Fork of the Virgin River on gauge ESTU1.
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: 1133513, 1189053, 1189049, 1133516, 1189621, 1189293, 1133514, 1189623, 1133517, 1189625, 1189202, 1189203.