After a break from thunderstorms in early September, moisture returned to much of Utah for the 2nd week of the month. These storms produced flash flooding in southern Utah and an isolated severe wind gust 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.
After a break from thunderstorms in early September, moisture returned to much of Utah for the 2nd week of the month. These storms produced flash flooding in southern Utah and an isolated severe wind gust 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 9, 2:51 PM MST, 24 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SALT LAKE CITY UT 351 PM MDT FRI SEP 9 2011 .SYNOPSIS....AN UPPER LOW WILL MOVE WESTWARD TO THE CALIFORNIA COAST BY SATURDAY. A RESULTANT INCREASING SOUTHERLY FLOW WILL SPREAD MOISTURE NORTHWARD ACROSS THE REGION THROUGH EARLY NEXT WEEK. && .DISCUSSION...WEAKLY DEFINED TROUGH REMAINS CENTERED SOMEWHERE AROUND NORTHERN ARIZONA/SOUTHERN UTAH THIS AFTERNOON. PWS ARE RUNNING SOMEWHERE IN THE 0.7 TO 0.9 INCH RANGE ACROSS MUCH OF THE STATE. COMBINED WITH THE SHORTWAVE ENERGY AROUND...THIS IS ALLOWING FOR SCATTERED CONVECTION OVER THE HIGHER TERRAIN OF CENTRAL AND SOUTHERN UTAH. UNUSUAL EASTERLY COMPONENT TO THE FLOW ALOFT IS ALLOWING FOR SLOW WESTWARD MOVEMENT OF DEVELOPING CELLS. THE TROUGH IS EXPECTED TO CONTINUE WESTWARD BEFORE CLOSING OFF NEAR THE SOUTHERN CALIFORNIA COAST DURING THE DAY TOMORROW. SHORTWAVES EJECTING FROM THIS SYSTEM WILL ALLOW FOR ADDITIONAL INSTABILITY OVER THE FORECAST AREA OVER THE NEXT FEW DAYS WITH PWS REMAINING ABOVE AVERAGE UNDER SOUTHERLY FLOW ALOFT. MODELS INDICATE THAT THE FLOW ALOFT WILL DEVELOP A WESTERLY COMPONENT BY MONDAY AS THE TROUGH MOVES A BIT NORTHWARD...ALLOWING THE AIRMASS TO DRY OUT JUST A LITTLE BIT. STILL...ENOUGH MOISTURE WILL REMAIN FOR AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS THROUGH THE END OF THE FORECAST PERIOD. LATEST GFS AND ECMWF REMAIN IN GOOD AGREEMENT ABOUT THE CALIFORNIA LOW THROUGH WEDNESDAY AFTERNOON...AS EACH BRINGS IT IN WEST CENTRAL ARIZONA AT THAT TIME. THE GLOBAL MODELS TEND TO DIVERGE AFTER WEDNESDAY. THE ECMWF BRINGS THE WEAKENED LOW ACROSS SOUTHERN UTAH BY THURSDAY NIGHT...RESULTING IN INCREASED MOISTURE AND INSTABILITY ACROSS THE FORECAST AREA DURING THE DAY THURSDAY. THE 12Z GFS...HOWEVER...SHOWS THE SYSTEM STALLING OVER ARIZONA BEFORE DISSIPATING BY SATURDAY WHICH WOULD BE A BIT OF A DRIER SOLUTION. RUN-TO-RUN CONSISTENCY IN THE EXTENDED PERIOD HAS BEEN POOR SO FAR...SO HAVE LITTLE CONFIDENCE IN EITHER SOLUTION. STILL...THINK THAT IT WILL BE SOMEWHAT MOIST AND UNSTABLE REGARDLESS...SO HAVE KEPT POPS ABOVE CLIMO THROUGH DAY 7. && .AVIATION...SHOWER AND THUNDERSTORM ACTIVITY IS EXPECTED TO INCREASE IN AND AROUND THE SLC TERMINAL THROUGH EARLY THIS EVENING. THERE WILL BE OCCASIONAL BRIEF RAIN SHOWERS WITH A 20 PERCENT CHANCE OF THUNDERSTORMS IMPACTING THE TERMINAL THROUGH 04Z. THUNDERSTORMS MAY PRODUCE GUSTY AND ERRATIC WINDS. OUTSIDE OF THESE STORMS...PREVAILING WINDS WILL BE FROM THE NORTH...WITH SOME EASTERLY COMPONENT ACROSS THE SOUTHERN END OF THE RUNWAY COMPLEX. && .FIRE WEATHER...A BROAD AREA OF LOW PRESSURE OVER THE SOUTHERN GREAT BASIN WILL ALLOW MOISTURE TO SLOWLY SPREAD NORTH ACROSS UTAH DURING THE UPCOMING WEEKEND THROUGH EARLY NEXT WEEK. SCATTERED THUNDERSTORMS OVER CENTRAL AND SOUTHERN UTAH THIS AFTERNOON WILL EXTEND FARTHER NORTH INTO NORTHERN UTAH BOTH SATURDAY AND SUNDAY. ALONG THE LEADING EDGE OF THIS MOISTURE THERE WILL BE A THREAT OF DRY THUNDERSTORMS ACROSS NORTHERN UTAH SATURDAY. AN UPWARD TREND IN COVERAGE OF SHOWERS AND THUNDERSTORMS AND IN AMOUNT OF PRECIPITATION WILL OCCUR THROUGH THE WEEKEND. A SOUTHWESTERLY FLOW DEVELOPS BY MONDAY WHICH SHOULD BEGIN A SLOW DOWNWARD TREND IN MOISTURE AND THEREFORE COVERAGE OF SHOWERS AND THUNDERSTORMS...ESPECIALLY OVER SOUTHWEST UTAH BY MONDAY AND WEST CENTRAL AND CENTRAL UTAH BY TUESDAY. ENOUGH MOISTURE REMAINS ELSEWHERE FOR A THREAT OF THUNDERSTORMS. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...NONE. WY...NONE. && PUBLIC...TRAPHAGAN FIRE WEATHER...STRUTHWOLF AVIATION...CHENG 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)
The Cedar City radar (KICX), 68 km away, was scanning. The volume nearest the first event began at 22:16 UTC.
2 flash flood, 1 thunderstorm wind. Local standard time, as filed.
A Kanab Visitor Center ranger reported a large flash flood in upper Johnson Canyon.
The Utah Department of Transportation reported a flash flood near Rockville, with water flowing across State Route 9.
The Lake Point I-80 sensor recorded a maximum wind gust of 63 mph.
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: 347915, 347916, 346615.