Thunderstorms producing heavy rain led to several flash floods across southern Utah in the middle of September. A few of these floods were located in and around Zion National Park.
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.
Thunderstorms producing heavy rain led to several flash floods across southern Utah in the middle of September. A few of these floods were located in and around Zion National Park. One report of large hail was also received during this time period.
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 13, 3:01 PM MST, 1 hour 44 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SALT LAKE CITY UT 401 PM MDT TUE SEP 13 2011 .SYNOPSIS...THE UPPER LOW OVER SOUTHERN CALIFORNIA WILL SLOWLY MOVE EAST THROUGH THURSDAY. THE AIRMASS ASSOCIATED WITH THE LOW PRESSURE WILL REMAIN MOIST AND UNSTABLE ACROSS MAINLY SOUTHERN AND EASTERN UTAH THROUGH MIDWEEK. A SERIES OF FAST MOVING DISTURBANCES WILL IMPACT THE NORTH LATE WEEK INTO THE WEEKEND. && .DISCUSSION...CIRCULATION CENTER THAT WAS QUITE NOTICEABLE IN MORNING WATER VAPOR IMAGERY OVER NORTH-CENTRAL NEVADA IS SHOWING SIGNS OF BECOMING ABSORBED IN THE MORE DOMINANT UPPER LOW OVER SOCAL. LIFT ASSOCIATED WITH THE FORMER CIRCULATION CENTER HAS PROVEN TO BECOME MORE EXPANSIVE THIS AFTERNOON AND NOW EXTENDS INTO WESTERN ARIZONA. WIDESPREAD SHOWERS AND THUNDERSTORMS HAVE BEEN THE NORM TODAY IN THE VICINITY OF SAID CIRCULATION...AND WILL MAKE A PUSH NORTH AND EAST TONIGHT AS THE UPPER LOW CONTINUES TO CHUG EAST. ACROSS OUR FORECAST AREA CONVECTION HAS BEEN THUS FAR MORE ISOLATED AND PRIMED BY DIURNAL INSTABILITY...FOCUSED OVER FAR SOUTHERN AND SOUTHWESTERN UTAH THIS AFTERNOON. HAVE CONTINUED TO RAISE POPS TONIGHT ACROSS FAR SOUTHERN UTAH AS THAT REGION WILL BE ON THE FRINGE OF THE AFOREMENTIONED LOW CENTER AND ASSOCIATED LIFT. BULK OF PRECIP SHOULD REMAIN JUST TO OUR SOUTH AND MORE STRATIFORM IN NATURE BUT NOCTURNAL CONVECTION IS EXPECTED ROLL NORTH ACROSS THE BORDER. GENERALLY SCATTERED PRECIP IN THE FORM OF SHOWERS AND EMBEDDED ISOLATED THUNDERSTORMS ARE EXPECTED. AREAL COVERAGE OF PRECIP WEDNESDAY WILL CONTINUE TO FOCUS JUST NORTH AND EAST OF SAID LOW CENTER AS IT CONTINUES TO SLOWLY WORK EAST INTO AND THROUGH CENTRAL ARIZONA. HAVE MAINTAINED LIKELY POPS ACROSS THE SOUTHERN MOUNTAINS AND SOUTHEASTERN VALLEYS AS PROXIMITY SHOULD BE CLOSE ENOUGH FOR ADDITIONAL DYNAMIC LIFT OF AN ALREADY MOIST AIRMASS. ELSEWHERE CONVECTION WILL REMAIN MORE RUN-OF-THE-MILL WITH TERRAIN BASED BUILDUPS AND PULSEY TYPE CELLS AS PER THE LAST SEVERAL DAYS. IN GENERAL WEATHER ACROSS THE NORTHERN VALLEYS WILL REMAIN DRY WITH NEAR SEASONAL TEMPS. DYNAMIC INFLUENCE OF THE ABOVE MENTIONED UPPER LOW WILL BEGIN TO WANE THURSDAY AS IT TRANSITIONS EAST INTO COLORADO. A SOMEWHAT MOIST AND DIURNALLY UNSTABLE AIRMASS WILL REMAIN IN PLACE INTO FRIDAY...BUT WILL TRANSITION TO A MORE PROGRESSIVE AND ACTIVE LATE WEEK/WEEKEND PERIOD ACROSS THE NORTH. AT LEAST TWO FAST MOVING SHORT WAVES WILL RIPPLE THROUGH IN MEAN WESTERLY FLOW BY SUNDAY MORNING...WITH FIRST ARRIVING BY FRIDAY EVENING. WEAK BAROCLINICITY/COLD ADVECTION WILL OCCUR WITH EACH OWING TO A COOLER AND SHOWERY PERIOD DURING THAT TIME. COOL AND RATHER DRY CONDITIONS WILL SET UP EARLY NEXT WEEK AS DRIER MID LEVEL AIR PUNCHES IN FROM THE WEST...WITH CONTINUED DRY CONDITIONS AND A MODEST WARMING TREND INTO MIDWEEK BENEATH AMPLIFYING RIDGING. && .AVIATION...VFR CONDITIONS WILL PERSIST AT THE SLC TERMINAL THROUGH THE EVENING HOURS. NORTHWEST WINDS WILL PERSIST UNTIL BETWEEN 02Z-04Z WHEN A SWITCH TO THE SOUTHEAST DRAINAGE WINDS IS EXPECTED. A FEW BUILD-UPS ARE FORECAST OVER THE NEARBY TERRAIN WITH ONLY A 10 PERCENT CHANCE OF A SHOWER OR THUNDERSTORM AFFECTING THE TERMINAL. && .FIRE WEATHER...A BROAD STORM SYSTEM CURRENTLY CENTERED OVER SOUTHERN CALIFORNIA IS FORECAST TO WEAKEN AS IT MOVES EAST ACROSS SOUTHERN NEVADA WEDNESDAY AND ARIZONA BY THURSDAY. THIS TRACK WILL CAUSE A MOIST FLOW TO CONTINUE OVER SOUTHERN UTAH BRINGING SCATTERED SHOWERS AND THUNDERSTORMS TO THAT AREA FOR THE NEXT COUPLE OF DAYS. FARTHER NORTH THE ABSENCE OF ANY DISCERNIBLE DISTURBANCES WILL RESULT IN MAINLY DRY CONDITIONS WITH ONLY ISOLATED AFTERNOON AND EVENING THUNDERSTORMS OVER THE MOUNTAINS. DAYTIME HUMIDITY LEVELS ARE FORECAST TO REMAIN ELEVATED THROUGH AT LEAST FRIDAY ACROSS THE ENTIRE REGION WITH VERY LITTLE CHANCE OF ANY AREA REACHING CRITICAL LEVELS. A TROUGH MOVING INTO THE PACIFIC NORTHWEST BY FRIDAY WILL LIKELY INCREASE THE WINDS ALOFT OVER WESTERN AREAS BUT WITH RELATIVE HUMIDITIES REMAINING ABOVE CRITICAL LEVELS THIS DOES NOT LOOK TO BE MUCH OF A THREAT. HOWEVER...IT IS CLOSE ENOUGH TO WARRANT KEEPING AN EYE ON AS THE EVENT NEARS. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...NONE. WY...NONE. && MERRILL/STRUTHWOLF/ROGOWSKI FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT... HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE) FOR FREQUENTLY ASKED QUESTIONS ABOUT THE AREA FORECAST DISCUSSION VISIT... HTTP://WEATHER.GOV/SALTLAKECITY/GENERAL/AFD_FAQS.PHP (ALL LOWER CASE)
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE SALT LAKE CITY UT 630 AM MDT TUE SEP 13 2011 UTZ001>016-019>021-517-518-WYZ021-141300- CACHE VALLEY/UTAH PORTION-NORTHERN WASATCH FRONT- SALT LAKE AND TOOELE VALLEYS-SOUTHERN WASATCH FRONT- GREAT SALT LAKE DESERT AND MOUNTAINS-WASATCH MOUNTAIN VALLEYS- WASATCH MOUNTAINS I-80 NORTH-WASATCH MOUNTAINS SOUTH OF I-80- WESTERN UINTA MOUNTAINS-WASATCH PLATEAU/BOOK CLIFFS- WESTERN UINTA BASIN-CASTLE COUNTRY-SAN RAFAEL SWELL- SANPETE/SEVIER VALLEYS-WEST CENTRAL UTAH-SOUTHWEST UTAH- UTAHS DIXIE AND ZION NATIONAL PARK-SOUTH CENTRAL UTAH- GLEN CANYON RECREATION AREA/LAKE POWELL-CENTRAL MOUNTAINS- SOUTHERN MOUNTAINS-SOUTHWEST WYOMING- 630 AM MDT TUE SEP 13 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE WESTERN TWO THIRDS OF UTAH AND SOUTHWEST WYOMING. .DAY ONE...TONIGHT ISOLATED SHOWERS AND THUNDERSTORMS ACROSS EXTREME SOUTHWEST UTAH EARLY THIS MORNING WILL INCREASE IN AREAL COVERAGE THIS AFTERNOON THROUGH TONIGHT. LOCALLY HEAVY RAIN...GUSTY WINDS AND CLOUD-TO-GROUND LIGHTNING WILL ACCOMPANY THE THUNDERSTORM ACTIVITY. ACROSS NORTHERN UTAH AND SOUTHWEST WYOMING THE THREAT OF THUNDERSTORMS WILL BE SUBSTANTIALLY LESS...WITH ANYTHING STORMS THAT DEVELOP CONFINED MAINLY TO THE HIGHER TERRAIN. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY AND UNSETTLED WEATHER PATTERN WILL SET MIDWEEK AS LOW PRESSURE TRACKS SLOWLY EAST ALONG THE BORDER WITH ARIZONA. SHOWERS AND THUNDERSTORMS WILL COVER A LARGE PORTION OF SOUTHERN UTAH WEDNESDAY THROUGH AT LEAST EARLY THURSDAY. HEAVY RAINFALL COULD ACCOMPANY SOME OF THE STRONGER THUNDERSTORMS WEDNESDAY. NORTHERN UTAH AND SOUTHWEST WYOMING WILL SEE SUBSTANTIALLY LESS SHOWER AND THUNDERSTORM ACTIVITY MIDWEEK. A SERIES OF WEATHER DISTURBANCES WILL RACE EAST ACROSS THE NORTHERN ROCKIES AND NORTHERN GREAT BASIN LATE IN THE WEEK. SOMEWHAT COOLER TEMPERATURES ALONG WITH A THREAT OF SHOWERS AND THUNDERSTORMS WILL EXIST WITH THESE PASSING WEATHER DISTURBANCES FOR FAR NORTHERN UTAH. MUCH DRIER AIR WILL MOVE INTO NORTHWEST UTAH LATE IN THE WEEKEND... AND SPREAD ACROSS THE REMAINDER OF THE STATE EARLY NEXT WEEK. TEMPERATURES WILL START NEXT WEEK BELOW NORMAL...THEN BEGIN TO SLOWLY CLIMB AS THE WEEK PROGRESSES. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT... HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)
The Cedar City radar (KICX), 43 km away, was scanning. The volume nearest the first event began at 23:43 UTC.
9 flash flood, 1 hail. Local standard time, as filed.
Large flash floods were reported in Pine Creek and Clear Creek in Zion National Park, with flowing water as much as 7 to 8 feet deep.
Flash flooding was reported in Zion National Park along the East Fork of the Virgin River, with the gauge along this river rising to 1665 cfs.
Heavy rain over the Fort Pearce Wash caused flash flooding along that drainage, with the measured flow at the gauge going from 0 cfs to 763 cfs in a single hour.
The Big Water Visitors Center reported a very large flash flood in the Wahweap drainage.
Flash flooding was reported along Fortymile Creek.
Heavy rain caused flash flooding along the Paria River drainage. The gauge on the Paria near Kanab went from 185 cfs to 1212 cfs in one hour.
Flash flooding occurred in many locations of Zion National Park, with floods reported over a large portion of the southern half of the park. Pine Creek and Spry Canyon both experienced large floods, with water in Pine Creek reportedly 6 to 7 feet high. Large rocks and other debris impacted some of the roads around the park. In addition, many of the smaller drainages that flow south to Rockville experienced flooding.
Flash flooding occurred in Crack Canyon, Little Wildhorse Canyon, and other washes near the Little Wildhorse Canyon trailhead. The floods were generally large and hikers caught in Crack Canyon had to run from the water, eventually making it back to the road before the water caught up with them.
Hikers who were caught in Crack Canyon during a thunderstorm reported hail that was approximately 1 inch in diameter.
Moderate to heavy rainfall fell over a broad area near Capitol Reef National Park. This initially caused flash flooding along Sulphur Creek and other parts of Capitol Reef. Eventually this water made its way downstream, causing flash flooding along the Dirty Devil River, which went from 538 to 1419 cfs in a few hours.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Utah in 2011Every state in 2011This day in weather historyWarnings in Utah, September 2011
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: 347920, 347922, 347926, 347923, 347924, 347927, 347929, 347931, 346617, 347933.