Monsoonal moisture in easterly flow aloft brought showers and thunderstorms to the mountains and deserts each afternoon and evening. The activity on the 9th was mainly in the upper deserts, San Bernardino Mountains and the Inland Empire near Lake Elsinore.
Every event with a place to put it; 3 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 SGX wrote it up.
Monsoonal moisture in easterly flow aloft brought showers and thunderstorms to the mountains and deserts each afternoon and evening. The activity on the 9th was mainly in the upper deserts, San Bernardino Mountains and the Inland Empire near Lake Elsinore. Flooding was reported along Highway 74 in Lake Elsinore with 3 to 5 inches of water covering the roadway, along with several downed trees, and a land spout in the nearby city of Perris. Outflow boundaries from storms created strong winds which picked up dust and lowered visibility in the Coachella Valley and near Borrego Springs. Visibility was also lowered to near zero at times with wind gusts around 60 MPH reported in the areas. Storms were more widespread on the 10th as a trough of low pressure drifted north from Mexico. Thunderstorms occurred over most mountain and desert locations, as well as the Inland Empire. Flash flooding was reported in Forest Falls and along Highway 76 in northern San Diego County. Highway 76 was closed for about an hour in the afternoon due to 12 to 18 inches of mud and debris in the road.
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 San Diego, CA wrote its last area forecast discussion before the first event at Sep 9, 12:40 PM PST, 20 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN DIEGO CA 140 PM PDT SUN SEP 9 2012 .SYNOPSIS... MOISTURE FROM AN UPPER LEVEL LOW OVER NORTHERN BAJA WILL RESULT IN SCATTERED SHOWERS WITH POSSIBLE THUNDERSTORMS OVER THE MOUNTAINS...DESERTS AND VALLEYS THROUGH TUESDAY MORNING. A STRAY SHOWER OR THUNDERSTORM MAY AFFECT THE COAST AS WELL. CHANCES FOR SHOWERS AND THUNDERSTORMS DECREASE TUESDAY AS THE UPPER LOW MOVES INTO ARIZONA. COOLING EXPECTED THROUGH TUESDAY DUE TO INCREASED CLOUDINESS AND LOW PRESSURE ALOFT. WARMING WITH COASTAL NIGHT AND MORNING LOW CLOUDS AND FOG FOR WEDNESDAY THROUGH SATURDAY AS HIGH PRESSURE BUILDS ALOFT. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... BANDS OF MID-TO-HIGH LEVEL CLOUDS WITH EMBEDDED LIGHT SHOWERS CONTINUE TO MOVE OVER PORTIONS OF THE FORECAST AREA THIS AFTERNOON...ACCORDING TO VISIBLE SATELLITE AND RADAR. RADAR IS ALSO SHOWING SOME TERRAIN BASED SHOWERS AND THUNDERSTORMS OVER THE HIGH DESERTS...SAN BERNARDINO MOUNTAINS AND NEAR TEMECULA. MEANWHILE...WATER VAPOR SATELLITE SHOWS AN UPPER LOW SETTING UP OVER NORTHERN BAJA...RESULTING IN NUMEROUS THUNDERSTORMS IN THAT AREA. THE 12Z MIRAMAR SOUNDING SHOWS A MOIST AND UNSTABLE ATMOSPHERE...WITH 1.87 INCHES OF PRECIPITABLE WATER. WINDS ARE OUT OF THE EAST AT ABOUT 20 KNOTS UP THROUGH 550 MB...AND THEN TURNING MORE OUT OF THE NORTH TO NORTHEAST AT 15-20 KNOTS ABOVE THAT. THESE WINDS SHOULD BE STRONG ENOUGH TO KEEP STORMS TODAY FROM SITTING OVER ONE AREA FOR TOO LONG...REDUCING THE RISK OF FLASH FLOODING. WITH THE BULK OF THE MID AND HIGH CLOUDS OVER SOUTHERN PARTS OF THE FORECAST AREA...NORTHERN AREAS SAW MORE SUNSHINE...AND THUS THEY HAVE GOTTEN MORE SURFACE HEATING. THEREFORE...THE SAN BERNARDINO COUNTY MOUNTAINS ARE SEEING THE MOST THUNDERSTORMS SO FAR TODAY. HOWEVER...THUNDERSTORMS AND SHOWERS...BOTH ELEVATED AND TERRAIN BASED...WILL CONTINUE TO BE POSSIBLE OVER THE SAN DIEGO AND RIVERSIDE COUNTY MOUNTAINS AND DESERTS AS WELL. WITH THE NEARBY UPPER LOW...SOME INSTABILITY...AND PLENTIFUL MOISTURE...ELEVATED CONVECTION IS LIKELY TO CONTINUE DURING THE OVERNIGHT HOURS. IT WILL BE MAINLY SCATTERED LIGHT TO MODERATE SHOWERS WITH POSSIBLY AN EMBEDDED THUNDERSTORM OR TWO. IF A VORTICITY MAX MOVES THROUGH...THIS WOULD FURTHER ENHANCE THE CHANCES FOR MORE WIDESPREAD SHOWERS AND EMBEDDED THUNDERSTORMS. COASTAL AREAS MAY SEE A STRAY SPRINKLE THROUGH MONDAY AFTERNOON. AS FOR TEMPERATURES...COOLING WILL COMMENCE TODAY WITH THE INCREASED CLOUD COVER AND LOW PRESSURE ALOFT. MODELS AGREE WITH KEEPING THE UPPER LOW OVER NORTHERN BAJA THROUGH MONDAY AFTERNOON BEFORE MOVING IT OUT BY TUESDAY MORNING. WITH LINGERING MOISTURE...THERE WILL CONTINUE TO BE A CHANCE OF THUNDERSTORMS THROUGH MONDAY EVENING FOR EVERYWHERE EXCEPT THE COAST. ASSUMING CLOUDS CLEAR OUT ENOUGH FOR SUFFICIENT SURFACE HEATING...TERRAIN BASED THUNDERSTORMS WILL ALSO BE LIKELY OVER THE MOUNTAINS AND DESERTS MONDAY AFTERNOON. POINT SOUNDINGS INDICATE THAT MID-TO-UPPER LEVEL WINDS WILL BE WEAKER TOMORROW...WHICH MEANS THAT THESE STORMS MAY BE MORE LIABLE TO SIT OVER ONE SPOT FOR A LONGER PERIOD OF TIME. NOCTURNAL SHOWERS/THUNDERSTORMS MAY BE POSSIBLE OVER EASTERN AREAS MONDAY NIGHT AS WELL...SO HAVE INTRODUCED SLIGHT CHANCE OF SHOWERS/THUNDERSTORMS IN FOR THAT TIME PERIOD. LEFTOVER MOISTURE TUESDAY AFTERNOON WILL BRING A SLIGHT CHANCE OF THUNDERSTORMS/SHOWERS OVER THE MOUNTAINS AS THE UPPER LOW MAKES ITS WAY INTO ARIZONA. MARINE LAYER STRATUS LIKELY TO RETURN TO THE COAST AND VALLEYS TUESDAY NIGHT AS DRIER WESTERLY FLOW MOVES IN ALOFT AND ONSHORE FLOW STRENGTHENS AT THE SURFACE. A WARMING TREND WILL BEGIN WEDNESDAY AND CONTINUE INTO SATURDAY AS HIGH PRESSURE BUILDS ALOFT. THE INCREASING HIGH PRESSURE WILL ALSO PRODUCE A SHALLOWER MARINE LAYER...RESULTING IN NIGHT AND MORNING STRATUS OVER THE COAST AND POSSIBLY INTO THE WESTERN INLAND VALLEYS. MOUNTAINS AND DESERTS WILL BE DRY...WITH PROBABLY ONLY A FEW CUMULUS AT BEST DURING THE AFTERNOONS. && .AVIATION... 092000Z...COAST/VALLEYS...MOSTLY BROKEN CLOUDS WILL CONTINUE ABOVE 8000 FT MSL THIS AFTERNOON...WITH ISOLATED/SCATTERED SHRA/TSRA...ESPECIALLY IN THE VALLEYS. TIMING OF ANY PRECIP WILL BE VARIABLE...BUT ACTIVITY WILL PEAK BETWEEN 21Z AND 01Z. SHRA/TSRA COULD IMPACT KONT...KRAL...KHMT...KF70...KRNM...KSEE...KMYF...KSDM AND POSSIBLY EVEN KSAN. FOR LATE TONIGHT/EARLY MONDAY...STRATUS WILL BE PATCHY ALONG THE COAST BUT WILL PROBABLY ONLY BRING A FEW HOURS OF CIGS...1000 FEET OR LESS...TO ANY OF THE COASTAL AIRPORTS SUCH AS KSAN OR KCRQ. THERE IS A SLIGHT CHANCE OF SHRA/TSRA MONDAY. MTNS/DESERTS...SCATTERED SHRA/TSRA WITH BASES AROUND 8000 FT MSL AND TOPS TO 40000 FT MSL COULD OCCUR AT ANY TIME THROUGH MONDAY BUT ARE MOST LIKELY THIS AFTERNOON AND AGAIN MONDAY AFTERNOON. THIS HAS THE POTENTIAL TO BRING LIGHTNING STRIKES WITHIN 5 NM OF KPSP/KTRM. LOCAL SFC GUSTS TO 35 KNOTS ARE POSSIBLE NEAR THUNDERSTORMS. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && PUBLIC...HARRISON AVIATION/MARINE...MAXWELL
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE SAN DIEGO CA 108 PM PDT SUN SEP 9 2012 CAZ042-043-048-050-055>058-060>062-PZZ750-775-101130- ORANGE COUNTY COASTAL AREAS-SAN DIEGO COUNTY COASTAL AREAS- SAN BERNARDINO AND RIVERSIDE COUNTY VALLEYS-THE INLAND EMPIRE- SAN DIEGO COUNTY VALLEYS-SAN BERNARDINO COUNTY MOUNTAINS- RIVERSIDE COUNTY MOUNTAINS-SANTA ANA MOUNTAINS AND FOOTHILLS- SAN DIEGO COUNTY MOUNTAINS-APPLE AND LUCERNE VALLEYS- COACHELLA VALLEY-SAN DIEGO COUNTY DESERTS- COASTAL WATERS FROM SAN MATEO POINT TO THE MEXICAN BORDER AND OUT 30 NM- WATERS FROM SAN MATEO POINT TO THE MEXICAN BORDER EXTENDING 30 TO 60 NM OUT INCLUDING SAN CLEMENTE ISLAND- 108 PM PDT SUN SEP 9 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EXTREME SOUTHWESTERN CALIFORNIA. .DAY ONE...THIS AFTERNOON AND TONIGHT. AN UPPER LEVEL LOW SOUTH OF THE MEXICAN BORDER WILL CONTINUE TO BRING SCATTERED LIGHT TO MODERATE SHOWERS AND POSSIBLE THUNDERSTORMS TO THE VALLEYS...MOUNTAINS AND DESERTS THROUGH TONIGHT. THUNDERSTORMS WILL BRING BRIEF HEAVY DOWNPOURS AND POSSIBLE STRONG WIND GUSTS. THE FLASH FLOOD POTENTIAL INDEX IS MODERATE OVER THE SAN BERNARDINO COUNTY MOUNTAINS. THUNDERSTORMS ARE EXPECTED TO DEVELOP AND ISOLATED FLASH FLOODING IS POSSIBLE. THE FLASH FLOOD POTENTIAL INDEX OVER THE REST OF THE FORECAST AREA IS LOW. THE RISK OF FLASH FLOODING IS MINIMAL. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY. SCATTERED LIGHT TO MODERATE SHOWERS AND ISOLATED THUNDERSTORMS WILL CONTINUE THROUGH MONDAY EVENING FOR THE VALLEYS...MOUNTAINS AND DESERTS AS THE UPPER LOW LINGERS SOUTH OF THE BORDER. EXPECT HEAVY DOWNPOURS...FREQUENT LIGHTNING AND POSSIBLE STRONG WIND GUSTS FROM THUNDERSTORMS. THUNDERSTORM AND SHOWER CHANCES WILL DECREASE MONDAY NIGHT THROUGH TUESDAY MORNING. SLIGHT CHANCE OF THUNDERSTORMS OVER THE MOUNTAINS ON TUESDAY AFTERNOON. FOR MONDAY...THE FLASH FLOOD POTENTIAL INDEX IS MODERATE. THUNDERSTORMS ARE EXPECTED TO DEVELOP AND ISOLATED FLASH FLOODING IS POSSIBLE. .SPOTTER INFORMATION STATEMENT... SKYWARN WEATHER ACTIVATION IS NOT REQUESTED FOR THIS AREA... HOWEVER WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS. SKYWARN WEATHER ACTIVATION MAY BE NEEDED TOMORROW. HARRISON
The Santa Ana Mts radar (KSOX), 38 km away, was scanning. The volume nearest the first event began at 21:00 UTC.
4 flood, 3 flash flood, 2 thunderstorm wind, 2 high wind, 1 tornado, 1 dust storm, 1 heavy rain. Local standard time, as filed.
A land spout was observed at 1330 PST along interstate 215 and highway 74 in Perris. No funnel was observed at the cloud base, and the land spout remained nearly stationary. Pictures and a video were submitted by spotters.
An NWS employee reported 3 to 5 inches of water flowing across the intersection of highway 74 and Lincoln in Lake Elsinore.
NWS employee reported 2 to 3 inch thick tree limbs down due to thunderstorms in Lake Elsinore around 1400 PST. Wind gust estimated around 55 MPH.
Law Enforcement reported an oak tree blown down across Lilac Rd near the intersection of San Luis Rey Drive. A newspaper article reported additional trees blown down across Lilac Road near the intersection of Couser Canyon Road.
A NWS employee reported three large pine trees downed by wind along Highway 76 south of Palomar Mountain. The largest of the uprooted pine trees was 18 to 20 inches in diameter, and healthy. A weather spotter estimated a 40 MPH wind gust in the area. The SDGE weather station at Cuca Ranch reported a wind gust of 42 MPH just before 1630 PST.
Wind gusts at the Thermal ASOS gusted over 45 mph between 1916 and 1944 PST with a peak gust of 61 mph at 1928 PST. The ASOS reported visibility between three-quarters of a mile and 3 miles in blowing dust during that time frame.
Strong winds and low visibility in blowing dust forced several vehicles to pull over on Highway 86 in Mecca. The Department of Highways reported visibility of three-quarters of a mile at 1925 PST near Mecca. The ASOS reported visibility between three-quarters of a mile and 3 miles during that time frame. The Palm Springs ASOS also reported visibility between one-quarter and one-half mile with winds gusting to 47 mph between 1948 and 2053 PST. A spotter in Cathedral City also reported visibility down to one-eighth of a mile in blowing dust with wind gusts to 36 mph.
The SDGE station at Borrego Springs measured sustained winds of 34 mph with gusts to 60 mph at 1930 PST. Law enforcement reported visibility of less than one-sixteenth of a mile (300 feet) in blowing dust during that time.
A spotter reported four inches of water on Mountain Avenue in the city of San Jacinto near Hemet. The Riverside County sheriff closed the roadway. |A mesonet station in the Valle Vista/Hemet area recorded a one-hour rainfall amount of 0.81 inches.
A heavy downpour resulted in standing water on Interstate 8 between Boulevard and Inkopah, as well as along portions of Highways 80 and 94 in that area. |Small hail of one-quarter of an inch or less and reduced visibility in heavy rain also occurred with this storm.|The Border Patrol station in Boulevard suffered damages from the heavy rain as well when mud was forced through the doors into the garage.|Between 1050 and 1250 PST, the Boulevard mesonet station recorded 0.71 inches of rain.
Mill Creek in Forest Falls was running 100 feet wide at one point with significant debris flowing with it. Police evacuated some people in the town of Forest Falls.|The Yucaipa Ridge mesonet station recorded approximately 3 inches of rain between 1130 and 1230 PST. The Heart Bar mesonet station, in the mountains upstream of Mill creek, recorded 2.84 inches of rain during that same hour.
The mesonet station of Eastern Tanks at La Jolla Amago recorded 1.46 inches of rain between 1311 and 1400 PST.|The mesonet station at the La Jolla Indian Reservation recorded 1.54 inches of rain between 1317 and 1405 PST.
A combination of debris and 6 inches of water flowing across National Trails Highway at Barbosa Road caused several vehicles to get stuck, resulting in CHP closing the highway for approximately 2 hours. |National Trails Highway was also closed at Hodge Road due to flooding.
Highway 76 east of Rincon was closed for one hour from 1430 to 1530 PST due to a flash flooding-induced debris flow 12-18 inches deep on the roadway.
Spotter SDG447 reported 0.84 inches of rain between 1430 and 1500 PST, which resulted in flooded roadways in the San Diego Country Estates area.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2012Every state in 2012This day in weather historyThe tornado archive for California, 2012Warnings in California, 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: 411603, 411604, 411605, 411606, 413201, 413203, 413208, 413209, 413210, 413213, 413214, 413215, 413216, 413217.