An active monsoon surge brought thunderstorms producing heavy rain, damaging wind gusts, and hail across the state.
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.
An active monsoon surge brought 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 Aug 1, 2:58 AM MST, 2 minutes earlier.
Area Forecast Discussion
National Weather Service Salt Lake City UT
358 AM MDT Sun Aug 1 2021
.SYNOPSIS...A monsoonal airmass will remain in place across the
region through Monday. A warming and drying trend will follow for
midweek.
&&
.SHORT TERM (Through 12Z Wednesday)...A robust monsoonal airmass
remains in place across the forecast area early this morning,
characterized by PW values in excess of 1 inch and dew points in
the upper 50s to low 60s. Showers which have persisted overnight
across northern and central Utah continue to diminish early this
morning, which will leave mostly sunny to partly cloudy skies for
the morning hours with only isolated lingering showers.
A shortwave trough currently lifting through the lower Colorado
River Valley of southeast CA/western AZ will lift into the
southern Great Basin this afternoon, with the associated jet
nosing into southwest Utah. Ahead of this wave daytime heating
will yield another round of showers and thunderstorms initiating
over the higher terrain, then moving northward. Large scale ascent
associated with the approaching wave along with deep layer shear
associated with the upper jet will allow for organized convection
capable of efficient rainfall processes. This convection is
expected to congeal as it lifts north through central and
eventually northern Utah during the late afternoon and evening
hours. Have gone ahead with a Flash Flood Watch for southern and
central Utah, as well as the southern Wasatch Front/southern
Wasatch owing to the Ether Hollow burn scar in Utah County.
The upper trough will slowly meander eastward across the area
Monday. May see lingering showers persist across northern Utah
within a region of upper level diffluence Monday morning, followed
by another round of showers and thunderstorms Monday afternoon and
evening mainly east of I-15. In the wake of this wave, will see a
drying trend heading into Tuesday with lingering moisture
maintaining a chance for convection across the northeastern CWA.
.LONG TERM (After 12Z Wednesday)... A rather mundane extended
forecast period lies ahead as the forecast area begins to see the
end of an extended monsoonal moisture residence across the area. A
building ridge is anticipated to take control by the middle of the
work week ahead, allowing for drying surface conditions alongside
warming temperatures. With the axis of this ridge cresting overhead
on Wednesday, should see temperatures linger right around near
normal levels. However, as this ridge axis begins translating
eastward from the influence of an offshore trough moving inland,
increased southerly flow across the region will allow for a rise in
temperatures as an airmass is advected from the Mojave. This trough
should brush by the northwestern corner of Utah, which will likely
bring some noteworthy implications on the forecast.
In addition to some of the warmer temperatures of the forecast
period, should also see an uptick in wind speeds across primarily
western and southern Utah, as well as decreasing surface relative
humidities. In a typical dry pattern, this setup would warrant fire
weather concerns across the area. However, given the recent trends
in abundant precipitation across the area and the associated
response in increased fuel moisture, not quite sure if fire weather
will be of high concern this time around. Will need to monitor
trends in fuel moisture going forward... but things are looking good
so far.
By Friday, ensemble guidance supports an overall flattening of the
mean ridge due to the aforementioned trough, allowing temperatures
to decrease/ return to near normal levels as we return to a more
zonally oriented flow. Daily buildups and weak convective showers
will be possible over the high terrain going through the weekend,
especially across the southern half of the area. However, given the
lack of moisture transport/ deep layer moisture, it's going to be
hard to develop any appreciable rains in these areas.
&&
.AVIATION...
KSLC...VFR conditions are expected to be maintained through the
valid TAF period over the KSLC terminal, with light southerly
drainage flows expected to return to a northerly upvalley flow after
18-19Z. Biggest threat of the day will be gusty and erratic outflow
winds from developing afternoon thunderstorm activity. Thunderstorms
are expected to begin developing over the surrounding terrain around
18Z. There is a 40% chance that thunderstorms directly impact the
terminal, specifically between 20-00Z. An area of showers will
continue into the area during the evening hours, potentially
maintaining CIGs around 8-9kft AGL.
Rest of Utah and southwest Wyoming...VFR conditions are expected
across a majority of the area through the valid TAF period, with the
exception of terminals directly impacted by heavy rainfall.
Afternoon convection is expected to develop across the area from
~18Z onward. As with most thunderstorm activity, the largest threat
looks to be associated with gusty and erratic outflow winds. Most
convection should subside by 03-04Z, however, an area of sustained
showers is anticipated through ~06-07Z across northern and western
Utah.
&&
.FIRE WEATHER...Ample monsoonal moisture will remain in place
across the area today. As a weather system moves north into the
Great Basin, numerous showers and thunderstorms capable of
producing locally heavy rainfall can be expected this afternoon
and evening. The combination of storms and cloud cover will also
keep temperatures below normal, with daytime relative humidity
remaining elevated along with excellent overnight recovery.
Moisture will linger through Monday maintaining daytime showers
and thunderstorms, particularly east of I-15. A warming and drying
trend will follow for midweek as high pressure aloft builds
across the Great Basin.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Flash Flood Watch from noon MDT today through this evening for
UTZ106-111-113-115>131.
WY...None.
&&
Seaman/Webber
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.phpHazardous Weather Outlook National Weather Service Salt Lake City UT 541 AM MDT Sat Jul 31 2021 UTZ101>131-WYZ021-011200- 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- 541 AM MDT Sat Jul 31 2021 This Hazardous Weather Outlook is for the western two thirds of Utah and southwest Wyoming. .DAY ONE...Today and Tonight Showers and thunderstorms capable of producing heavy rain and gusty winds are expected this afternoon and evening. There is a potential for localized flash flooding, especially in south wester Utah and in prone areas such as slot canyons, burn scars, areas of steep terrain, and normally dry washes and streams. .DAYS TWO THROUGH SEVEN...Sunday through Friday The moist airmass will remain in place through Monday. Daily showers and thunderstorms capable of heavy rain and gusty winds will occur each afternoon and evening across much of the forecast area. Drier air will move into the area beginning Tuesday, and remain in place through the remainder of the week. .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
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
1010 PM MDT SAT JUL 31 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0715 PM FLASH FLOOD 3 SSW ZION NP 37.21N 112.98W
07/31/2021 WASHINGTON UT OTHER FEDERAL
USGS STREAM GAUGE RECORDED FLOWS OF 2400 CFS ON THE NORTH
FORK OF THE VIRGIN RIVER NEAR SPRINGDALE.
&&
ALEX.DESMETPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
1055 PM MDT SAT JUL 31 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0630 PM FLASH FLOOD 3 SE SPRINGDALE 37.16N 112.96W
07/31/2021 WASHINGTON UT OTHER FEDERAL
STREAM GAUGE ON THE EAST FORK OF THE VIRGIN RIVER
RECORDED A PEAK FLOW OF 2790 CFS.
&&
ALEX.DESMETThe Cedar City radar (KICX), 97 km away, was scanning. The volume nearest the first event began at 10:00 UTC.
13 flash flood, 3 thunderstorm wind, 3 flood, 2 hail. Local standard time, as filed.
The Paria River near Kanab gauge recorded a peak flow of 865 CFS.
An observer reported 3 feet of rocks, mud, and water flooded into a ranch basement and nearly moved a second home off its foundation near the Crawford Mountains.
Capitol Reef National Park officials reported flash flooding on Sulphur Creek and the Fremont River, along with muddy conditions on Scenic Drive. The initial flood wave through Sulphur Creek contained black boulders.
County dispatch reported Kingston Canyon was underwater with rock and debris over a portion of state Route 62.
An automated weather station recorded a peak wind gust of 63 mph.
Penny-sized hail was reported.
Quarter-sized hail was reported via social media.
A debris flow moved across a road in Timber Canyon.
Widespread flash flooding occurred in Enoch and Cedar City, with up to 300 homes damaged by flood waters. Water rescues were performed, and cars were swept off the road. Interstate 15 was closed during the event. Numerous roads were eroded by floodwaters, and Fiddlers Canyon was reported underwater.
The Bolinder Field-Tooele Valley Airport AWOS recorded a peak wind gust of 60 mph.
In Tooele, 37 homes were flooded. Additionally, multiple roads were closed due to flooding.
An automated weather station recorded a peak wind gust of 62 mph.
Big Cottonwood Canyon Road was closed due to flash flooding carrying debris and rocks across the roadway.
Flash flooding was reported on the Bountiful Bench, with water flowing through a home.
Multiple roadways across the greater Salt Lake Valley were flooded. A portion of Interstate 80 was closed near 1300 East, as was Interstate 215 near Millcreek.
Numerous reports, videos, and photos of water over roadways near Utah Valley University in the vicinity of Interstate 15 were received.
Several lane on Interstate 15 near Bountiful were closed due to standing water. Hill Field Road near Hill Air Force Base was flooded. Basement flooding occurred in Centerville.
A significant flood wave carrying debris moved down Bear Creek Canyon, sweeping away mining vehicles at the Gentry Mountain Mine. Several miners were caught in the flood waters, with one miner able to save himself by clinging to a tree a quarter mile down the drainage. Another miner was not able to escape the flood waters and was found deceased 6 miles downstream. Another Mine car was flipped 8 times in the flood waters, but the miners were able to kick out the windows and escape. Significant infrastructure damage occurred at the Mine.
UDOT reported two flash floods the Trail Mountain Fire burn scar flowed across state Route 31 between milepost 40 and milepost 44.
Capitol Reef National Park officials reported flash flooding in Grand Wash.
Capitol Reef National Park officials reported flash flooding on several drainages in the Park.
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 |
|---|---|---|---|---|---|
| Flash Flood, Emery | 2021-08-01 | 48 | Male | Outside/Open Areas | 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, August 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: 981829, 981837, 981841, 981843, 981918, 981919, 981920, 983199, 981865, 981923, 981868, 981924, 983188, 981872, 981931, 981946, 981942, 981898, 983202, 981902, 981911.