A low pressure system interacted with deep monsoon moisture to produce widespread thunderstorms and flash flooding. A few storms also produced severe weather.
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 VEF wrote it up.
A low pressure system interacted with deep monsoon moisture to produce widespread thunderstorms and flash flooding. A few storms also produced severe weather.
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 Las Vegas, NV wrote its last area forecast discussion before the first event at Sep 11, 2:04 AM PST, 26 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LAS VEGAS NV 304 AM PDT TUE SEP 11 2012 .SYNOPSIS...SCATTERED THUNDERSTORMS WILL BE SEEN TODAY WITH LOCALLY HEAVY RAINFALL POSSIBLE ACROSS MAINLY LINCOLN...CLARK...AND MOHAVE COUNTIES. DRYING FROM THE WEST ON WEDNESDAY WILL DECREASE THUNDERSTORM ACTIVITY WITH DRY CONDITIONS EXPECTED OVER THE AREA ON THURSDAY WHICH WILL CONTINUE INTO THE UPCOMING WEEKEND. BELOW NORMAL TEMPERATURES EXPECTED TODAY WITH A SLOW WARMING THEN TAKING PLACE INTO THE WEEKEND. && .SHORT TERM...TODAY THROUGH THURSDAY...TWO SEPARATE LOW PRESSURE SYSTEMS TO BE AFFECTING THE CWA DURING THE DAY TODAY. THE FIRST SYSTEM OVER NORTHERN MEXICO/SOUTHERN ARIZONA WILL CONTINUE TO SHIFT EAST DURING THE DAY. HOWEVER THIS SYSTEM HAS BEEN RESPONSIBLE FOR WIDESPREAD SHOWERS/THUNDERSTORMS ACROSS MAINLY MOHAVE COUNTY THIS MORNING WITH ACTIVITY SLOWLY SHIFTING NORTH ACROSS THE AREA. DYNAMICS/MOISTURE FROM THIS SYSTEM WILL CONTINUE TO KEEP THUNDERSTORMS/SHOWERS GOING THROUGH MUCH OF THE DAY OVER THE SOUTHEAST PORTION OF THE CWA. SOME CONCERN HOWEVER IS THAT THE ACTIVITY THAT IS TAKING PLACE CURRENTLY MAY HAMPER FURTHER CONVECTION DURING THE DAY TODAY. THE SECOND SYSTEM WILL BE A WEAK UPPER LOW MOVING INTO CENTRAL CALIFORNIA WHICH WILL BE SHIFTING EAST DURING THE DAY ALSO. A WEAK BOUNDARY/DIFFLUENCE ALOFT/POSSIBLE WEAK JET DYNAMICS ALL POINT TO CURRENT THUNDERSTORM ACTIVITY OVER CENTRAL NEVADA CONTINUING THROUGH THE DAY AND SHIFTING SOUTHEAST INTO MAINLY LINCOLN COUNTY AS THE SYSTEM SHIFTS ACROSS CENTRAL NEVADA TODAY. GOOD INSTABILITY/PW VALUES OF OVER AN INCH ALL POINT TO LOCALLY HEAVY RAINFALL AND WILL EXTEND THE FLASH FLOOD WATCH FOR LINCOLN/CLARK/MOHAVE COUNTIES INTO THIS EVENING WITH THIS PACKAGE. AT THE SAME TIME...MID LEVEL DRYING AS SEEN ON WATER VAPOR SHOULD BRING A DECREASED CHANCE OF THUNDERSTORMS TO THE WESTERN PORTION OF THE CWA TODAY...ESPECIALLY THE WESTERN TWO THIRDS OF SAN BERNARDINO COUNTY AND MUCH OF INYO COUNTY AND WILL END THE FLASH FLOOD WATCH FOR THIS AREA. HOWEVER..WITH THIS SAID...LOW LEVEL DRYING HAS YET TO TAKE PLACE AND NOT OUT OF THE QUESTION THAT ISOLATED THUNDERSTORMS WILL BE SEEN...ESPECIALLY OVER THE MOUNTAINS THIS AFTERNOON/EVENING FOR THIS AREA TOO. BY WEDNESDAY...DRYING ALOFT SHOULD START TO BECOME THE DOMINANT FACTOR WITH THUNDERSTORMS BEING CONFINED TO MOHAVE/LINCOLN/AND THE MOUNTAINS OF CLARK COUNTY. FURTHER DRYING IS EXPECTED ON THURSDAY WITH ALL SHORT TERM MODELS SHOWING THAT A BUILDING RIDGE OVER THE AREA WILL SHIFT THE MOISTURE WELL TO THE EAST OF THE CWA. CLOUDS/SHOWERS/THUNDERSTORMS WILL KEEP TEMPERATURES...ESPECIALLY EAST BELOW NORMAL FOR TODAY...BUT WITH THE RIDGE BUILDING OVER THE AREA...WARMING TEMPERATURES EXPECTED INTO THURSDAY. .LONG TERM...DRY CONDITIONS AND SEASONAL TEMPERATURES ARE EXPECTED FRIDAY THROUGH THE BEGINNING OF NEXT WEEK. HIGH PRESSURE ACROSS THE REGION ON FRIDAY WILL FLATTEN AND REESTABLISH WEST OF THE FORECAST AREA OVER THE WEEKEND AS AN AREA OF LOW PRESSURE DIVES SOUTH ACROSS THE NORTHERN PLAINS. THE GFS DOES INDICATE A SHORTWAVE ASSOCIATED WITH THIS FEATURE PASSING ACROSS LINCOLN AND MOHAVE COUNTY ON SUNDAY/MONDAY...WHICH COULD POTENTIALLY CREATE JUST ENOUGH INSTABILITY TO RESULT IN ISOLATED THUNDERSTORMS...BUT OPTED TO KEEP THE FORECAST DRY BASED ON OVERALL MODEL CONSENSUS. DRY NORTHWESTERLY FLOW WILL THEN REMAIN IN PLACE THROUGH THE END OF THE PERIOD. && .AVIATION...FOR MCCARRAN...THUNDERSTORMS WILL DEVELOP AGAIN TODAY...INITIALLY BY LATE MORNING/EARLY AFTERNOON OVER THE SURROUNDING HIGHER TERRAIN. OVERALL STORM MOTION SHOULD BE SLOW...AND FEEL PROBABILITY OF ANY STORMS MOVING OFF THE MOUNTAINS AND OVER KLAS ARE NOT HIGH ENOUGH TO INCLUDE AS A TEMPO GROUP IN THE TAF AT THIS TIME. HOWEVER...THERE IS STILL A CHANCE OF A STORM DEVELOPING OVER KLAS...WITH THE BEST TIMES DURING THE AFTERNOON BEING BETWEEN 20Z AND 00Z. A WEAK DISTURBANCE MOVING ACROSS SOUTHERN NEVADA WILL THEN HELP TRIGGER SCATTERED CONVECTION DURING THE EVENING. OUTSIDE OF ANY THUNDERSTORM INFLUENCE...WINDS WILL REMAIN OUT OF THE SOUTH. FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST CALIFORNIA...THUNDERSTORMS WILL BE POSSIBLE OVER THE NEXT 24 HOURS MAINLY ACROSS NEVADA AND ARIZONA LOCATIONS...WITH COVERAGE BECOMING MORE WIDESPREAD BY THE AFTERNOON. ANY STORM WILL BE CAPABLE OF PRODUCING GUSTY WINDS...HEAVY RAIN...AND SMALL HAIL. OUTSIDE OF ANY STORM INFLUENCE...WINDS WILL BE OUT OF THE SOUTHEAST TO SOUTH AROUND 10-18KTS. && .VEF WATCHES/WARNINGS/ADVISORIES... NV...FLASH FLOOD WATCH THROUGH THIS EVENING FOR NVZ015-016-018>022. AZ...FLASH FLOOD WATCH THROUGH THIS EVENING FOR AZZ001>003-036. CA...FLASH FLOOD WATCH THROUGH THIS EVENING FOR CAZ527. && JENSEN/KENNEDY HTTP://WEATHER.GOV/LASVEGAS
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE LAS VEGAS NV 522 AM PDT MON SEP 10 2012 AZZ001>003-036-CAZ522>527-NVZ014>022-110330- NORTHWEST PLATEAU-LOWER COLORADO RIVER VALLEY-NORTHWEST DESERTS- LAKE MEAD NATIONAL RECREATION AREA-DEATH VALLEY NATIONAL PARK- WESTERN MOJAVE DESERT-EASTERN MOJAVE DESERT-MORONGO BASIN- CADIZ BASIN-SAN BERNARDINO COUNTY-UPPER COLORADO RIVER VALLEY- ESMERALDA AND CENTRAL NYE COUNTY-LINCOLN COUNTY- NORTHEAST CLARK COUNTY-WESTERN CLARK AND SOUTHERN NYE COUNTY- SHEEP RANGE-SPRING MOUNTAINS-LAS VEGAS VALLEY- SOUTHERN CLARK COUNTY- 522 AM PDT MON SEP 10 2012 /522 AM MST MON SEP 10 2012/ THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHWEST ARIZONA...CALIFORNIA AND SOUTHERN NEVADA. .DAY ONE...TODAY AND TONIGHT A FLASH FLOOD WATCH REMAINS IN EFFECT FOR NORTHWEST ARIZONA... SOUTHERN NEVADA AND MUCH OF SOUTHEAST CALIFORNIA FROM 9 AM THIS MORNING THROUGH TONIGHT. DEEP MOISTURE HAS MOVED UP FROM NORTHERN MEXICO AND SOUTHERN ARIZONA AND WILL CONTINUE TO BE ENHANCED TODAY AND TONIGHT. THIS WILL PROVIDE FOR SCATTERED TO NUMEROUS THUNDERSTORM COVERAGE ACROSS THE AREA. THE PRIMARY THREAT FROM THUNDERSTORMS WILL BE THE POTENTIAL FOR HEAVY RAIN AND FLASH FLOODING. STRONG GUSTY WINDS MAY ALSO OCCUR WITH ANY STRONGER STORMS THAT DEVELOP. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY THUNDERSTORMS CAPABLE OF HEAVY RAIN AND FLASH FLOODING WILL BE POSSIBLE AGAIN ON TUESDAY...PRIMARILY OVER EASTERN SAN BERNARDINO COUNTY IN CALIFORNIA...CLARK AND LINCOLN COUNTIES IN SOUTHERN NEVADA...AND NORTHWEST ARIZONA. DRIER AIR WILL CONTINUE TO WORK ITS WAY INTO THE AREA TUESDAY NIGHT AND WEDNESDAY. THUNDERSTORM ACTIVITY WILL BE REDUCED FURTHER ON WEDNESDAY...WITH ISOLATED TO SCATTERED THUNDERSTORMS ACROSS CLARK...LINCOLN AND MOHAVE COUNTIES. DRY CONDITIONS ARE EXPECTED AREA WIDE ON THURSDAY AND FRIDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS REQUESTED FOR THIS AFTERNOON AND EVENING. SPOTTERS ARE ENCOURAGED TO REPORT ANY SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. CAZ519>521-110330- EASTERN SIERRA SLOPES-OWENS VALLEY-WHITE MOUNTAINS OF INYO COUNTY- 522 AM PDT MON SEP 10 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CALIFORNIA. .DAY ONE...TODAY AND TONIGHT ISOLATED THUNDERSTORMS ARE EXPECTED ACROSS THE LOWER TERRAIN AND SCATTERED THUNDERSTORMS IN THE HIGHER ELEVATIONS THIS AFTERNOON AND EVENING. THE MAIN THREAT WITH THESE STORMS WILL BE HEAVY RAIN. STRONG GUSTY WINDS MAY ALSO OCCUR WITH ANY STRONGER STORMS THAT DEVELOP. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY ISOLATED THUNDERSTORMS ARE EXPECTED ACROSS THE HIGHER ELEVATIONS ON TUESDAY. THE MAIN THREAT WITH THESE STORMS WILL BE GUSTY WINDS. DRIER AIR WILL THEN BE IN PLACE FOR THE REMAINDER OF THE PERIOD. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME. HOWEVER... SPOTTERS ARE ENCOURAGED TO REPORT ANY SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.
The San Joaquin Valley radar (KHNX), 236 km away, was scanning. The volume nearest the first event began at 10:27 UTC.
5 flash flood. Local standard time, as filed.
Flash flooding washed mud and debris over Highway 265 near Silver Peak as well as Highway 95 in eastern Esmeralda County.
Three inches of water along with mud and debris flowed down Mesa Blvd.
Major flash flooding affected much of the Las Vegas Valley. Numerous roads were closed due to water, mud, and rocks; and several people had to be rescued from vehicles. Many vehicles in parking lots were submerged in muddy water. Many homes, condos, and businesses flooded, and three dogs drowned in one home. Water got into buildings on the UNLV campus as well as a middle school and the MGM Grand Garden Arena. One landscaper died when flood waters swept him off his front-end loader.
Two feet of water flowed over a section of White Dome Road, and Valley of Fire State Park was evacuated and closed. In addition, Interstate 15 was closed due to flooding of the California Wash (near mile marker 75).
Highway 169 in Overton was closed near the Overton Wash, 1.5 feet of water flowed over Highway 168 in Moapa as well as Warm Spring Loop Road, and there were multiple road closures in Logandale.
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, Clark | 2012-09-11 | 31 | Male | Outside/Open Areas | Direct |
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Nevada in 2012Every state in 2012This day in weather historyWarnings in Nevada, September 2012
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: 402186, 402187, 402190, 402191, 402193.