Zion National Park had heavy rain and flash flooding along the Virgin River. Thunderstorms around Milford brought strong outflow winds.
Every event with a place to put it. Tap one for its entry below.
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.
Zion National Park had heavy rain and flash flooding along the Virgin River. Thunderstorms around Milford brought strong outflow winds.
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 10, 3:13 AM MST, 8 hours 47 minutes earlier.
Area Forecast Discussion National Weather Service Salt Lake City UT 413 AM MDT Thu Aug 10 2023 .SYNOPSIS...Southwesterly flow over the area will allow moisture to increase through Friday, remaining in place through the weekend. Drier air may move back into the area, but especially northern Utah, by the middle portion of next week. && .SHORT TERM (THROUGH 12Z SATURDAY)...An upper ridge over Utah this morning will shift eastward and become less amplified due to a couple of shortwave troughs. One such trough is currently tracking east across Montana, and is responsible for the flattening of the ridge. The other is a weak disturbance ejecting into SoCal and which is progged to develop into a closed low which will then settle into place over the SoCal Coast through the weekend. Southwesterly flow across southern Utah today will be advecting in a plume of moisture that exists across SoCal, far southern Nevada, and western Arizona. Latest PWAT analysis shows the 1 inch contour just outside the far southwest corner of Utah, with between 0.7-0.9 inches currently across southern Utah. Latest guidance suggests that PWATs could reach 1.2 inches across far southern Utah by this afternoon. With the flow turning more westerly this afternoon, however, the moisture is not expected to make it into northern Utah today. Showers and thunderstorms are expected to develop across southern and central Utah today as the moisture makes its way into the area. Some dynamic support exists with a jet streak crossing southern Utah this morning and then some upper diffluence this afternoon ahead of the upper low. While some areas on the leading edge of the moisture surge may see some high-based convection initially, dewpoints are already in the 50s at some sites across southwest Utah, so the low- levels may moisten fairly quickly and locally heavy rain will be possible. Some CAMs, especially many of the recent HRRR runs, have been excited about convection later this morning into the afternoon. However, there has not been much consistency between the various CAMs, as some also keep the strongest convection south of the Arizona border. Given this uncertainty, have held off on any Flash Flood Watches for the time being. That said, the best chance for flash flooding today will be across Washington and Kane Counties, and perhaps the Capitol Reef area if the lower levels moisten quickly enough there. As the upper low retrogrades to the SoCal coast, southwesterly flow returns, allowing the moisture to spread northward tomorrow, with 0.8-0.9 inch PWATs expected to reach northern Utah. Meanwhile, it is progged to dry slightly across southern Utah, but PWATs are expected to remain near 1 inch. However, there is expected to be less forcing tomorrow, so convection may be tied more to the higher terrain. .LONG TERM (After 12Z Saturday)...We will continue to contend with an area of low pressure to our west this weekend with building high pressure from the northwest. Daily shower and thunderstorm chances are expected in the southern two-thirds of the state as a result, especially over the higher terrain. A chance for a thunderstorm can't be ruled out across northern Utah, including along the Wasatch Front each afternoon. This pattern will remain in play until high pressure to our southeast kicks the low out to sea sometime early next week. At this point, no cluster mean is showing a different solution (in comparison to a possible solution from previous runs had that the low absorbing into another low to the north). As such, the forecast gradually will become more influenced by high pressure with a warming and drying trend. No real influence from an area of low pressure over Canada (and its subsequent cold front) are anticipated as these features are forecast to stay well to our north and northeast. && .AVIATION...KSLC...VFR conditions are forecast today with high based clouds anticipated. Breezy southerly winds this morning are expected through approximately 16z with gusts between 20 and 25 mph. Winds are forecast to shift out of the northwest early this afternoon and back southeast around 04z this evening. .REST OF UTAH AND SOUTHWEST WYOMING...Showers and thunderstorms are expected to impact southern Utah terminals this morning and this afternoon. A line of thunderstorms are forecast to track northeast from NV/AZ, impacting SGU to CDC between 14z and 21z. Brief MVFR conditions from reduced visibility are possible. Gusty outflow winds are also possible in or near thunderstorms; wind gusts of 40+ mph are possible. Additional thunderstorms may impact southern terminals through the afternoon; improving conditions are expected near or after 00z. Across northern Utah and southwest Wyoming, there's a less than 10% chance for showers and thunderstorms this afternoon at PVU; otherwise dry conditions are anticipated. && .FIRE WEATHER...Moisture will increase from the south and spread into central Utah today. This will bring higher humidities and generally scattered wet thunderstorms to southern and central Utah, with locally heavy rainfall possible. However, areas on the leading edge of this moisture surge could potentially see a brief period of dry thunderstorms initially before the storms trend wetter. The moisture will spread farther northward tomorrow, with the higher terrain of northern Utah expected to see mostly wet thunderstorms. This moisture will linger through the weekend and into the early part of next week. Heading into the middle part of next week, northern Utah will start to trend drier again while some moisture is expected to remain in place across southern Utah. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...None. WY...None. && Cheng/NDeSmet For more information from NOAA's National Weather Service visit... http://weather.gov/saltlakecity
The national radar mosaic for the moment the first event began.
1 flash flood, 1 thunderstorm wind. Local standard time, as filed.
Zion National Park rangers reported multiple large waterfalls throughout the park. Additionally, the river gage on the Virgin River at Virgin recorded an increase in flows from 77 cfs to 1604 cfs between 12:00 and 1:00 p.m. MDT.
A wind gust of 59 mph was recorded at the Milford ASOS.
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: 1189060, 1189288.