Several rounds of thunderstorms brought severe weather hazards to the state of Utah, including flash flooding in southern and eastern Utah, and damaging winds, hail, and a tornado in Northern Utah.
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.
Several rounds of thunderstorms brought severe weather hazards to the state of Utah, including flash flooding in southern and eastern Utah, and damaging winds, hail, and a tornado in 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 Sep 1, 2:54 AM MST, 4 hours 27 minutes earlier.
Area Forecast Discussion National Weather Service Salt Lake City UT 354 AM MDT Wed Sep 1 2021 .SYNOPSIS...Moisture associated with a monsoon surge and remnant moisture of what was once Hurricane Nora will continue to produce showers and thunderstorms with locally heavy rainfall across much of southern and eastern Utah into this evening. Showers and thunderstorms will persist into Thursday but coverage will be less. A high pressure ridge will begin to build into the area late this weekend and possibly persist into the middle of next week. && .SHORT TERM (Through 12Z/6AM MDT Saturday)... Early morning satellite and observational analysis reveals the presence of an area of low pressure situated across northwest Arizona. A broad area of upper divergence is noted extending north and east from this feature along a NE-SW oriented axis from southern Nevada through central Utah with a mid-level dry slot punching northward into south-central Utah. The NE-SW band of upper divergence is associated with an 80 knot upper jet which stretches NE-SW from NW Arizona NE into Colorado. In addition, a band of mid-level frontogenesis/deformation is present in this area as well. Embedded vorticity filaments are all working in concert to provide mesoscale enhancement to the background large- scale ascent. Efficient poleward moisture advection is noted on the 292-294K isentropic surfaces as well, continuing to advect deeper subtropical moisture northward into southern Utah. In addition, modest surface to mid-level CAPE is noted per mesoanalysis. Finally, PWATs of 2x normal for early September are analyzed early this morning and are expected to persist through the day. Plentiful moisture, lift and instability are combining to produce a broad area of moderate rain across southern Utah with localized heavy rain across portions of SW Utah early this morning. The band extends north and east through much of southern and eastern Utah. The northwestern edge of the precipitation gradient is remarkably sharp, currently extending from western Washington County NE through the eastern 2/3rds of Iron County and the eastern third of Beaver county. Farther south, a brief break in the action is noted across far south-central Utah in association with the poleward advecting mid-level dry slot. There is some uncertainty regarding how far north and west the band of moderate to heavy rain will extend this morning. The NBM is a bit too far south and east with the band, so some hand editing and blending with 06Z CAM runs has nudged the higher PoPs and QPFs more in line with trends. Some additional forecast edits may be needed later this morning should the farther north and east trends continue. Nonetheless, the heaviest rain should remain generally south and east of a Delta to Provo to Uintas line today. As we head through the day, the area of low pressure and associated dynamics will slowly shift eastward across southern Utah. Expect the greatest rain and thunderstorm coverage will shift eastward in association with the propagation of most efficient large- scale ascent. With regards to the earlier mentioned mid-level dry slot, CAMs/HREF ensemble suggest showers and thunderstorms will fill in here with any modest daytime heating, with convection getting a boost due to ample moisture and large- scale lift. Any of these thunderstorms will be capable of producing locally heavy rainfall as well. Farther west and later this afternoon and evening, a differential heating zone will locally enhance frontogenesis, and all high-resolution CAMs indicate additional shower and thunderstorm activity as a result, mainly across western Iron, Beaver and Millard counties later this afternoon into earlier this evening. Widespread QPF amounts of 0.50-1"+ is forecast through this evening across these areas. Even farther north across northwest/northern Utah and SW Wyoming, convection will be limited to an isolated shower or thunderstorm at best through tonight. Staying up north for a bit, a trailing mid-level trough will undergo modest amplification as it approaches from the northwest Thursday, passing across northern Utah and SW Wyoming Friday and Friday night. This will promote shower and thunderstorm activity across northern Utah and SW Wyoming from Thursday afternoon through Friday evening. CAMs may actually be a bit underdone given the scope of the ascent, so some upward adjustments may be needed here. This activity could produce locally gusty winds and small hail. This northern trough will promote continued SW flow -- and as a consequence smoke from western wildfires will likely increase and thicken across northern Utah and SW Wyoming through Thursday night. Shifting gears farther south, deeper moisture and lift will shift east of the area on Thursday. However, lingering low to mid-level moisture will combine with orographics and daytime heating along with modest lift courtesy of the incoming mid-level trough to promote isolated to scattered shower and thunderstorm activity Thursday afternoon and evening from the Wasatch all the way south along the higher terrain of central and southern Utah. With modest mid-level westerly flow in place, this convection will tend to develop over the terrain and drift eastward. Southern and central Utah will undergo a drying trend on Friday while isolated showers and thunderstorms linger across northern Utah and SW Wyoming associated with the passing mid-level trough. Well below normal temperatures across southern Utah will rebound back to near normal values by Friday, while temperatures across northern Utah and SW Wyoming drop to around 10 degrees below climatological normals in the wake of the passing mid-level trough. .LONG TERM (After 12Z/6AM MDT Saturday)... Drying out through the long term forecast period, with warming temperatures expected. Not much to write about in the long term forecast. There is considerably agreement amongst the ensemble members for a retrograded high pressure area to expand across much of the Intermountain West through the weekend. Both the ensemble members and the long range models are in agreement in developing a ridge/trough pattern, with the ridge encompassing much of the western and central CONUS. This pattern remains consistent through the entirety of the long term forecast period. What the means for Utah is the monsoon moisture tap will be turned off with drier and warmer weather over the weekend and into much of next week. Temperatures will climb above seasonal normals across the state, with triple digit heat holding on across southern Utah. && .HYDROLOGY... A strong moisture surge combined with remnant moisture from Nora will bring the threat of heavy rainfall to much of southern and eastern Utah into this evening. As a result, a Flash Flood Watch remains in effect through this evening. The highest threat of flash flooding will be in normally dry washes, slot canyons, slick rock areas, near recent burn scars and in steep canyons. Those will outdoor plans in these areas or with interests near flood prone locations should continue to monitor future forecasts. QPF amounts are generally forecast in the 0.50"-1" range across southern and central Utah, and will be highest where associated large-scale ascent and mesoscale ascent are juxtaposed. In these areas, locally higher amounts of 1-2" will be possible. && .AVIATION...KSLC...VFR conditions will prevail across the terminal through the valid TAF period. Southerly winds will increase after 19z, with gusts up to 18 knots expected. Vicinity thunderstorms after 19z could produce gusty and erratic outflow winds around the terminal. The best window for vicinity thunderstorms will be from 19- 04z. REST OF UTAH AND SOUTHWEST WYOMING...An area of moderate to heavy rain across southern Utah will continue to expand northward through the morning hours. MVFR conditions are occurring, associated with the heavier rain pockets. Additional development of showers and thunderstorms across central and northern is expected between 18- 19z. Expect gusty and erratic winds in and around thunderstorm cores. Outside of thunderstorms and the heavy rain, VFR conditions is expected across the airspace. Lingering high concentrations of smoke will be confined to northwest Utah. && .FIRE WEATHER...An area of low pressure and associated monsoonal moisture surge will impact much of southern and eastern Utah today with widespread rain with embedded thunderstorms. Rain will be locally heavy at times. Below average temperatures will accompany this activity today. Much drier conditions are expected over NW Utah with only isolated showers and thunderstorms. Widespread rains will slacken and move east of the area tonight, leaving isolated to scattered showers and thunderstorms along and east of the mountain spine for Thursday afternoon and evening. Isolated showers and thunderstorms will be possible over northern Utah on Friday while southern Utah begins to dry out and warm up. A ridge of high pressure is then forecast to build into the region from late this weekend into at least the middle of next week, bringing a return to above average temperatures and mainly dry conditions. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...Flash Flood Watch through this evening for UTZ113-117-120>131. WY...None. && ADeSmet/Woodward 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 357 AM MDT Wed Sep 1 2021 UTZ101>131-WYZ021-021000- Great Salt Lake Desert and Mountains-Tooele and Rush Valleys- Eastern Box Elder County-Northern Wasatch Front-Salt Lake Valley- Utah Valley-Cache Valley/Utah Portion-Wasatch Back- Bear Lake and Bear River Valley-Wasatch Mountains I-80 North- Wasatch Mountains South of I-80-Western Uinta Mountains- Wasatch Plateau/Book Cliffs-Western Uinta Basin- Western Millard and Juab Counties-Eastern Juab/Millard Counties- Central Mountains-Sanpete Valley-Sevier Valley-Castle Country- San Rafael Swell-Southwest Utah-Lower Washington County- Zion National Park-Southern Mountains-Upper Sevier River Valleys- Bryce Canyon Country-South Central Utah- Capitol Reef National Park and Vicinity-Western Canyonlands- Glen Canyon Recreation Area/Lake Powell-Southwest Wyoming- 357 AM MDT Wed Sep 1 2021 This Hazardous Weather Outlook is for the western two thirds of Utah and southwest Wyoming. .DAY ONE...Today and Tonight A strong moisture surge combined with remnant moisture from what once was Hurricane Nora will bring the threat of heavy rainfall to portions of southern, central and eastern Utah through this evening. The highest threat of flash flooding will be in normally dry washes, slot canyons, slick rock areas, near recent burn scars and in steep canyons. Those with outdoor plans in these areas or with interests near flood prone locations should continue to monitor future forecasts. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday Isolated to scattered showers and thunderstorms are expected along and east of high terrain areas on Thursday afternoon and evening as far western Utah dries out. Additional showers and thunderstorms are possible Friday afternoon across northern Utah and SW Wyoming. Smoke from western wildfires will continue to impact the northern third or so of Utah and southwest Wyoming through at least Thursday night. .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. 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
The Cedar City radar (KICX), 39 km away, was scanning. The volume nearest the first event began at 14:17 UTC.
4 flash flood, 4 hail, 3 thunderstorm wind, 2 flood, 1 tornado. Local standard time, as filed.
Zion National Park rangers reported flash flooding in slot canyons between Temple of the Sun and Twins.
Capitol Reef National Park officials reported 6 inches of water flowing across state Route 24 in several locations east of Fruita. UDOT also reported 6 inches of water flowing across state Route 24 between mileposts 81 and 84.
A significant flash flood occurred in the town of Hanksville, with nearly every structure in town impacted by flooding. Floodwaters were reportedly as deep as 6 feet in places. Rainfall totals were 1.2 inches in Hanksville, and were as high as 1.7 inches in the Henry Mountains. In Capitol Reef National Park, 1.66 inches fell.
The Fremont River overflowed its banks between Hanksville and Caineville, making state Route 24 impassible east of Capitol Reef National Park.
The Dirty Devil - Poison Springs Above Hanskville gauge indicated a rise from a baseline around 500 CFS to 14100 CFS, or from a gauge height of about 8 feet to about 21 feet. According to United States Geological Survey, the peak flow rate of 14100 CFS ranks as the 6th highest peak flow rate for all water years back to 1948. The peak gauge height of 21 feet ranks as the 3rd highest peak gauge height for all water years back to 1948.
The English Village Dugway automated weather station recorded a peak wind gust of 59 mph.
Hail up to 1 inch in diameter fell in Salt Lake City.
Hail up to 3/4 of an inch in diameter fell in East Mill Creek.
A tornado first touched down in North Salt Lake at Redwood Road and 900 W around 628 PM MDT. The tornado moved to the northeast through a mix of industrial and residential areas. The tornado produced EF0 damage (winds 65 to 85 MPH) to numerous trees and several homes in the Cloverdale neighborhood. The tornado continued to move off to the northeast, producing more EF0 damage to the Woods Cross Public Works building and a nearby construction site. The tornado reached peak intensity along 1100 W, producing EF1 damage (winds 86 to 110 MPH) where it uprooted a healthy mature tree and leaned a wooden power pole. The tornado continued to the north, weakening, but still producing EF0 damage before lifting off the ground.
The tornado then made a second touchdown in a field near 800 W where it produced EF0 damage to a business in the area and began moving northward along 800 W. Tree damage and minor property damage indicative of an EF0 tornado was widespread along this swath. Large diameter tree limbs (in excess of 12 inches) were broken off and deposited throughout the area. The tornado then dissipated in the area of 1500 S and Interstate 15 around 634 PM MDT.
The rating for this tornado is EF1 with winds as high as 110 MPH. The tornado had an intermittent track length of about 2 miles over 7 minutes and a max-width of approximately 350 yards with an average width of approximately 150 yards.
Hail up to 3/4 of an inch in diameter fell in Wood Cross.
Hail up to 3/4 of an inch in diameter fell in Rosedale.
The Escalante River gauge near Escalante rose from 375 CFS to a peak of 1840 CFS.
The Upper Cedar Mountain automated weather station recorded a peak wind gust of 59 mph.
The Interstate 80 at Milepost 81 Dolomite automated weather station recorded a peak wind gust of 58 mph.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Utah in 2021Every state in 2021This day in weather historyThe tornado archive for Utah, 2021Warnings in Utah, September 2021
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: 986712, 986713, 986717, 986715, 986716, 986702, 986707, 986708, 986709, 986710, 986711, 986714, 986703, 986704.