An active monsoon surge brought several back-to-back days of thunderstorms producing heavy rain, damaging wind gusts, and hail across the state.
Every event with a place to put it; 1 filed by county or forecast zone are drawn at its center, in a lighter ring. 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.
An active monsoon surge brought several back-to-back days of thunderstorms producing heavy rain, damaging wind gusts, and hail across the state.
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 Jul 18, 3:06 AM MST, 10 hours 36 minutes earlier.
Area Forecast Discussion National Weather Service Salt Lake City UT 406 AM MDT Sun Jul 18 2021 .SYNOPSIS...High pressure will remain across the region for much of the next week. Monsoonal moisture will begin to increase across southern Utah today, then spread across the remainder of the area and remain in place through the rest of the week. && .SHORT TERM (Through 12Z Wednesday)...Another day under a broad upper level ridge across the Interior West is in store for Utah to end this mid-July weekend. The edge of the next moisture surge is quite apparent on satellite imagery early this morning, with several additional shortwaves noted across Arizona. While the best forcing for showers this morning will push west of the area, a few isolated showers will be possible across far southern Utah through mid-morning. Expect precipitable water values across southern Utah to gradually increase, shifting to ~150% of normal by this afternoon. The previously mentioned moisture gradient/embedded shortwave should serve as a trigger point for convection across southwestern Utah this afternoon. SBCAPE values near 500-1000 J/kg can be expected across this area...with deep layer shear between 10-20 kts. Most CAM guidance focuses development across southwestern Utah during the afternoon...with convection hugging the Utah/Nevada border for much of the overnight hours in response to the gradual northward progression of the previously mentioned wave. Sunday will be a hot day across northern Utah...with temperatures approaching 100F for the northern valleys. Given how hot this summer has already been...this is more of a broken record than anything noteworthy for most individuals in these areas. As the Sunday convection gradually diminishes early Monday morning, another round of convection is expected Monday afternoon into Monday night. There will be two primary forcing mechanisms...one shifting northward from Arizona and another the result of an embedded wave shifting northeastward across northern Nevada. While HREF ensemble mean SBCAPE values are nothing to write home about (averaging around 500-750 J/kg across the state), deep layer shear will be near 20-25 kts across northern Utah Monday afternoon and evening. As a result of these two primary areas of forcing, CAMS are largely focusing convection across southern Utah, moving northward with the southern wave...with another round of convection shifting northeastward into northern Utah Monday evening into Monday night. With precipitable water values in the 150-200+% of normal range, this has the potential to bring a soaking rain to portions of Utah. As is typical, timing shortwaves this far out is wrought with potential issues...but this is something to watch for future shifts. By Tuesday, the ridge shifts subtly south and east in response to a shift in the upper trough near the Pacific Coast. The net result from this will likely be drier air shifting into northwestern Utah...suppressing convection across much of northern and potentially western Utah. Monsoon moisture will remain across much of eastern and southern Utah...with another round of convection expected Tuesday afternoon and evening. As far as flash flood potential...expect southwestern Utah to see thunderstorms with potentially heavy rain this afternoon and evening. This threat will likely shift to much of the state Monday. Those with outdoor plans in southern Utah should monitor forecasts and have a "plan B" if weather does not cooperate. Those near recent burn scars should continue to monitor forecasts and watch for future watches/warnings. .LONG TERM (After 12Z Wednesday)...The ridge will remain in place into the extended forecast. Ensemble guidance has good agreement in a weak trough moving eastward from the Pacific coast into Canada and some flattening of the ridge, but not enough to have a noticeable effect on weather conditions locally. Monsoon moisture will keep building in from the south with the ridge centered near the Colorado/Utah border. Precipitable water values upwards of 1" are expected in southern Utah. Values around 1" are expected in the north. Flash flooding will remain a threat with these thunderstorms. Ensemble solutions diverge later in the week. Nearly 3/4ths of EPS members retrograde the ridge westward, centering it over Nevada, resulting in drier conditions. A small percentage of CMCE and GEFS members also do that. The majority support the ridge staying nearly stationary or push it eastward. That solution is slightly more likely if you consider all members from the aforementioned ensemble guidance. If it plays out, shower and thunderstorms chances will last into the following week. If the solution largely influenced by the EPS does, drier conditions would be expected around Friday. && .AVIATION...KSLC...VFR conditions are expected through the valid TAF period. Southeast winds will transition to the northwest around 19Z. Scattered mid to high clouds are expected with dry conditions. Isolated to scattered thunderstorms will build into northern Utah in the evening, but the dry environment will result in gusty outflow winds being possible after 00Z. Rest of Utah and southwest Wyoming...VFR conditions are expected through the valid TAF period. Scattered showers and thunderstorms will start in the early afternoon in southern Utah. Showers and thunderstorms will build northward, but drier conditions will result in better chances for gusty outflow winds later in the afternoon into the evening. Thunderstorms will diminish after 03Z, but isolated to scattered rain showers will still be possible in southern Utah. && .FIRE WEATHER...High pressure will remain centered across the Four Corners region for much of the next week. As Utah remains on the west side of this high pressure, this will help to draw monsoonal moisture northward into the state for much of the week. Expect the first round of thunderstorms with wetting rain potential across southern Utah today, spreading north and east Monday. Any thunderstorms over the northern half of Utah will trend toward the dry side and may contain gusty and erratic winds. By Monday, most storms across the state will largely trend toward the wetter side. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...None. WY...None. && Kruse/Wilson 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 316 AM MDT Sun Jul 18 2021 UTZ101>131-WYZ021-190930- 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- 316 AM MDT Sun Jul 18 2021 This Hazardous Weather Outlook is for portions of central Utah... northern Utah...southern Utah...southwest Utah and southwest Wyoming. .DAY ONE...Today and Tonight Showers and thunderstorms will develop across the higher terrain of Utah this afternoon and evening. Any showers and thunderstorms will be capable of gusty and erratic winds. Thunderstorms across southern Utah will be capable of heavy rain. .DAYS TWO THROUGH SEVEN...Monday through Saturday Monsoonal moisture will remain across the region through most of the next week. Showers and thunderstorms will be capable of heavy rain, gusty winds and small hail each afternoon and evening. Those planning outdoor activities especially across particularly flood prone areas of southern Utah should continue to monitor future forecasts. .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 Salt Lake City radar (KMTX), 129 km away, was scanning. The volume nearest the first event began at 20:40 UTC.
15 flash flood, 11 thunderstorm wind, 3 heavy rain, 2 hail, 1 heat, 1 flood, 1 lightning. Local standard time, as filed.
The Vernon automated weather station recorded a peak wind gust of 59 mph.
The Vernon Hill automated weather station recorded a peak wind gust of 64 mph.
Flash flooding washed out the main access road to Old Irontown from State Route 56. Emergency managers stated the road was closed until repaired.
Water and debris flowed across State Route 21.
The English Village automated weather station recorded a peak wind gust of 62 mph.
The Romeo and Centerline automated weather stations both recorded peak wind gusts of 59 mph.
Urban flash flooding was reported in Cedar City. A video received via social media showing water flowing down streets near the Ashdown Subdivision.
Zion National Park officials reported flash flooding in both the main canyon and in tributaries feeding the canyon from the east.
Social media reports indicated urban flash flooding in Enoch. Radar estimates indicated in excess of 2 inches of rain.
Flash flooding occurred in a tributary of Shoal Creek. An abandoned pickup truck was observed submerged in the water.
Capitol Reef National Park officials reported flash flooding in Sulphur Creek, with water running 6-12 inches high. Also flash flooding occurred in the Fremont River and Grand Wash.
The Paria - Kanab gauge on the Paria River indicated a rise of 397 CFS, or about 1.5 feet.
A 9-year-old boy was found dead in a vehicle in American Fork on Wednesday, July 21, at around 1:45 p.m. It is believed the child was inside the car for approximately two hours before he was discovered. Temperatures in the vicinity of American Fork at the time were generally in the 90-95 degree Fahrenheit range.
A Capitol Reef National Park official shared a video of flash flooding in Sulphur Creek.
The Wendover Port of Entry automated weather station recorded a peak wind gust of 64 mph.
The Paria - Kanab gauge on the Paria River indicated a rise to 519 CFS, or about 1.5 feet.
An observer in Bryce Canyon National Park reported hail up to 1.5 inches in diameter.
A weather spotter reported water running down streets in Tropic.
A lightning bolt blew a four foot wide hole through the roof of a St. George home starting a fire. No one was hurt.
Beaver County dispatch and emergency management personnel reported street flooding in Milford with water 3 feet deep. In addition, debris from flooding was reported on State Route 21 near Milford. The Milford automated weather station recorded 1.10 inches of rain in one hour.
Widespread standing water and urban flooding was reported in Richfield. Radar estimates indicated 1-1.25 inches of rain over a brief period.
Grand Staircase-Escalante National Monument officials reported flash flooding along the Escalante River and Calf Creek.
The Paria - Kanab gauge on the Paria River indicated a 3 foot rise, with peak flows of 1800 CFS.
Capitol Reef National Park officials reported flash flooding in Sheets Gulch.
Runoff from a heavy rain event over the Coal Hollow Fire Burn Scar flowed over railroad tracks and onto the south shoulder of U.S. Highway 6.
A large tree was uprooted and crashed into a home in Butlerville, placing a hole in the roof. Damage to an awning was also noted. The time of the event was estimated from radar.
Hail up to 0.75 inches in diameter was reported.
Power lines were snapped in Murray, with multiple large trees uprooted throughout town. Carport and car damage occurred, as did damage to business signs and rooftops.
A wind gust of 74 mph was recorded in Bountiful.
An automated weather station recorded a 60 mph wind gust in Daybreak. Additionally, storm drains were overwhelmed by heavy rainfall.
Multiple trees fell on homes in the Midvale area. Additionally, power outages occurred.
Heavy rain over the Ether Hollow Fire Burn Scar produced a debris flow that moved across Quiet Meadows Lane on the outskirt of Mapleton.
In Salt Lake City, flooding with water in excess of a depth of 6 inches, occurred at the intersection of 100 S and 300 E. Flooding also occurred in common areas of a complex at 300 S and 300 W.
Downed trees damaged homes, roofing, and a shed.
As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.
| Event | Date | Age | Sex | Where | Kind |
|---|---|---|---|---|---|
| Heat, Utah Valley | 2021-07-21 | 9 | Male | Vehicle/Towed Trailer | Direct |
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Utah in 2021Every state in 2021This day in weather historyWarnings in Utah, July 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: 973774, 973775, 973600, 973599, 973776, 973777, 973601, 973602, 974276, 973603, 973605, 974239, 974534, 973606, 973778, 974264, 973779, 973607, 973780, 973608, 974277, 973609, 973615, 973610, 973611, 974266, 974267, 974268, 974269, 974272, 974274, 973616, 974284, 974275.