A cold and unstable air mass produced strong thunderstorms and flash flooding across Los Angeles county. The strongest storms occurred across the San Fernando and San Gabriel Valleys.
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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 LOX wrote it up.
A cold and unstable air mass produced strong thunderstorms and flash flooding across Los Angeles county. The strongest storms occurred across the San Fernando and San Gabriel Valleys.
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 Los Angeles, CA wrote its last area forecast discussion before the first event at Oct 11, 9:48 AM PST, 1 hour 57 minutes earlier.
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 1048 AM PDT THU OCT 11 2012 .SYNOPSIS... UPPER LEVEL LOW PRESSURE WILL SCATTERED SHOWERS AND A SLIGHT CHANCE OF THUNDERSTORMS TODAY AND TONIGHT. TEMPERATURES WILL BE WELL BELOW NORMAL TODAY...BUT A WARMING TREND WILL BEGIN TOMORROW AS THE LOW PRESSURE SYSTEM MOVES EAST. ABOVE NORMAL TEMPERTURES ARE EXPECTED STARTING SUNDAY...AS WEAK OFFSHORE FLOW DEVELOPS. && .SHORT TERM (TODAY-SAT)...THE FOCUS AREAS TODAY ARE AT THE EXTREME NORTHERN AND SOUTHERN REACHES OF OUR FORECAST AREA, NAMELY SLO COUNTY AND THE COASTAL WATERS OFF THE OC COAST. THE LOW IS CENTERED JUST SOUTH OF THE CHANNEL ISLANDS AND AREAS NEAR THE CENTER ARE THE LEAST ACTIVE AT THIS POINT. AIR MASS IS QUITE UNSTABLE TODAY WITH LI'S GENERALLY -2 TO -5, THOUGH STABILIZING SOMWHAT THROUGH THE DAY ACROSS SLO COUNTY AS TEMPS ALOFT START TO WARM BEHIND THE UPPER LOW. SO AS WE PROGRESS THROUGH THE AFTERNOON I EXPECT THE ACTIVITY IN THE NORTHERN AREAS TO SUBSIDE BUT CONTINUE IN THE SOUTH, ESPECIALLY LA COUNTY AND AREAS TO THE EAST AND SOUTH, WITH SMALLER CHANCES ACROSS VENTURA AND SBA COUNTIES. BIGGEST IMPACTS WILL BE WATERSPOUTS AND GUSTY WINDS OVER THE SOUTHERN COASTAL WATERS, SOME POSSIBLY MOVING ONSHORE, WHILE LAND AREAS, ESPECIALLY LA COUNTY, WILL BE SUSCEPTIBLE TO BRIEF HEAVY SHOWERS AND SMALL HAIL. ACTIVITY EXPECTED TO WIND DOWN QUICKLY THIS EVENING AS THE AIR MASS RAPIDLY STABILIZES WITH WARMER AIR ALOFT. 12Z NAM SHOWED A LITTLE IMPULSE MOVING THROUGH THE CENTRAL COAST FRIDAY MORNING WITH SOME LIGHT PRECIP PRESUMABLY FROM THE SYSTEM THAT IS CURRENTLY NEAR 140W JUST WEST OF THE SHORT WAVE RIDGE AXIS. WITH THE NAM SHOWING THE RIDGE AXIS STILL WEST OF THE COASTLINE FRIDAY MORNING THE DEVELOPMENT OF PRECIP EAST OF THE RIDGE AXIS SEEMS UNLIKELY UNLESS WE'RE STILL SEEING WRAP AROUND MOISTURE FROM THE UPPER LOW TO OUR EAST. GFS DOESN'T SEEM ENAMORED WITH THE PRECIP IDEA EITHER SO FOR NOW WILL KEEP THE FORECAST DRY AND JUST MONITOR THE SITUATION THROUGH THE DAY. ELSEWHERE, A DRY DAY EXPECTED FRIDAY WITH SLIGHTLY WARMER TEMPS. BETTER WARMING EXPECTED SAT AS WE START TO TRANSITION TO NORTHERLY LOW LEVEL FLOW AND RIDGING DEVELOPS ALOFT. POSSIBLY SOME GUSTY SUNDOWNER WINDS SATURDAY EVENING IN THE SBA AREA. ***FROM PREVIOUS DISCUSSION*** .LONG TERM (SUN-WED)... ALL EXTENDED MDLS AGREE THAT AN EAST PAC UPPER HIGH WILL NOSE INTO CENTRAL CALIFORNIA STARTING SUNDAY AND THEN CHANGING LITTLE MONDAY AND TUESDAY. BOTH EC AND GFS FURTHER INCREASE THE HIGH AND WEDNESDAY MAKING IT THE WARMEST DAY OF THE NEXT 7. THE GFS ALSO DEVELOPS A MODERATE OFFSHORE PUSH WHICH IF TRUE WILL REALLY BALLOON THE TEMPS UP ACROSS THE COASTS AND VLYS. EC MUCH LESS AGGRESSIVE AND WENT WITH THIS MORE CONSERVATIVE FCST. SKIES SHOULD BE MOSTLY CLEAR AS THERE DOES NOT LOOK LIKE ANY MARINE LAYER TRIGGERS...BUT IT IS NOT OUT OF THE QUESTION THAT SOME LOW CLOUDS COULD FORM MONDAY OR TUESDAY. MAX TEMPS WILL REACH NEAR OR SLIGHTLY ABOVE NORMAL SUNDAY AND THEN REMAIN CLOSE TO THOSE VALUES THROUGH TUESDAY WITH A COUPLE DEGREE BUMP UP WEDNESDAY. && .AVIATION...11/1800Z. MID/UPPER LEVEL LOW PRESSURE SYSTEM CENTERED OVER POINT CONCEPTION WILL SHIFT EAST WHILE A TROUGH OF LOW PRESSURE UPSTREAM APPROACHES. MID/UPPER LEVEL MODERATE SOUTH WINDS WILL BECOME MODERATE NORTHWEST AFTER 12/06Z. AIR MASS WILL REMAIN UNSTABLE AND MOIST THROUGH 12/09Z. THUNDERSTORMS TOPS APPROXIMATELY 35KFT WILL MOVE NORTHEAST APPROXIMATELY 10KT SOUTH AND EAST OF THE LOW CENTER AND SOUTHWEST APPROXIMATELY 15KT WEST AND NORTH OF THE CENTER. FREEZING LEVEL WAS APPROXIMATELY 8KFT THIS MORNING AND WILL DIFFER BY PLUS 3KFT AFTER 12/18Z. MARINE CLOUD FIELD OFF THE CENTRAL COAST WILL MOVE ASHORE WITH TOPS APPROXIMATELY 3KFT OVERNIGHT. KLAX...CHANCE OF -TSRA CIGS 040 AT TIMES THROUGH 11/20Z. THEN CHANCE -SHRA BETWEEN 11/20-12/07Z WITH CHANCE OF CIGS 040 AT TIMES BETWEEN 12/03-12/07Z. CHANCE CIGS 020 AT TIMES BETWEEN 12/11-12/15Z. KBUR...CHANCE -SHRA THROUGH 12/02Z. THEN CHANCE CIGS 025 BY 12/11Z. VIRTUALLY CERTAIN - 95-100% VERY LIKELY - 80-95% LIKELY - 60-80% CHANCE - 30-60% VERY UNLIKELY - 20% OR LESS && .LOX WATCHES/WARNINGS/ADVISORIES... MARINE WEATHER STATEMENT (SEE LAXMWSLOX). SPECIAL WEATHER STATEMENT (SEE LAXSPSLOX). && PUBLIC...MW/RORKE SYNOPSIS...SUKUP WWW.WEATHER.GOV/LOSANGELES
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 600 AM PDT THU OCT 11 2012 CAZ034>041-044>046-051>054-059-087-088-547-548-121300- SAN LUIS OBISPO COUNTY CENTRAL COAST- SANTA BARBARA COUNTY CENTRAL COAST-SANTA YNEZ VALLEY- SAN LUIS OBISPO COUNTY INTERIOR VALLEYS-CUYAMA VALLEY- SANTA BARBARA COUNTY SOUTH COAST-VENTURA COUNTY COAST- LOS ANGELES COUNTY COAST INCLUDING DOWNTOWN LOS ANGELES- VENTURA COUNTY INTERIOR VALLEYS-VENTURA COUNTY COASTAL VALLEYS- SANTA MONICA MOUNTAINS RECREATIONAL AREA- SAN LUIS OBISPO COUNTY MOUNTAINS- SANTA BARBARA COUNTY MOUNTAINS-VENTURA COUNTY MOUNTAINS- LOS ANGELES COUNTY MOUNTAINS EXCLUDING THE SANTA MONICA RANGE- ANTELOPE VALLEY-CATALINA ISLAND-SANTA CLARITA VALLEY- LOS ANGELES COUNTY SAN FERNANDO VALLEY- LOS ANGELES COUNTY SAN GABRIEL VALLEY- 600 AM PDT THU OCT 11 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHWESTERN CALIFORNIA. .DAY ONE... TODAY AND TONIGHT THERE WILL BE A CHANCE OF SHOWERS AND THUNDERSTORMS THROUGH THIS EVENING. SNOW LEVELS WILL BE ABOVE 7000 FEET. RAINFALL WILL BE LIGHT EXCEPT UNDER THUNDERSTORMS. * SPECIAL WEATHER STATEMENT..SEE WWUS86 KLOX - SPSLOX FOR DETAILS * .DAYS TWO THROUGH SEVEN... THURSDAY THROUGH TUESDAY NO HAZARDOUS WEATHER IS EXPECTED. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. RORKE
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OXNARD CA
848 AM PDT THU OCT 11 2012
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0838 AM WATER SPOUT 24 SSW OXNARD 33.88N 119.37W
10/11/2012 PZZ655 CA COAST GUARD
MARINER SITED AND RELAYED TO USCG
&&
BFThe Los Angeles radar (KVTX), 45 km away, was scanning. The volume nearest the first event began at 19:44 UTC.
2 flash flood, 1 heavy rain. Local standard time, as filed.
A trained weather spotter reported 1.50 inches of rainfall in 15 minutes in association with a strong thunderstorm.
A strong thunderstorm producing heavy rain and flash flooding in the community of La Canada. Flash flooding and debris flows closed Crown Street between Foothill Avenue and Baptiste Street.
A strong thunderstorm producing heavy rain and flash flooding in the San Gabriel Valley. California Highway Patrol reported 3 to 4 feet of water flooding all lanes of Interstate 710.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2012Every state in 2012This day in weather historyWarnings in California, October 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: 416272, 416270, 416271.