High pressure over the four-corners region resulted in an extended monsoonal flow pattern across Southern California. For several days, strong thunderstorms produced heavy rain, flash flooding and large hail across parts of Southern California.
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 LOX wrote it up.
High pressure over the four-corners region resulted in an extended monsoonal flow pattern across Southern California. For several days, strong thunderstorms produced heavy rain, flash flooding and large hail across parts of Southern California.
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 Jul 4, 1:30 PM PST, 15 minutes earlier.
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 230 PM PDT MON JUL 4 2011 .SYNOPSIS... HIGH PRESSURE WILL PERSIST INTO MIDWEEK AND WILL DRAW MOISTURE INTO THE REGION FOR POSSIBLE SHOWERS AND THUNDERSTORMS...MAINLY IN THE MOUNTAINS AND DESERTS...AND ABOVE NORMAL TEMPERATURES. A SLIGHT COOLING TREND BY MIDWEEK AS THE HIGH WEAKENS. ONSHORE FLOW IS EXPECTED TO DEVELOP AND THE MARINE LAYER WILL BEGIN TOAND LOWER THE TEMPERATURES TO AT OR BELOW SEASONAL NORMALS OVER THE WEEKEND. && .SHORT TERM (TODAY-THU)...HAVE ISSUED A FLASH FLOOD WATCH FOR VENTURA AND LOS ANGELES MOUNTAINS AS WELL AS THE DESERT THROUGH MIDNIGHT TONIGHT. A THUNDERSTORM IN THE VICINITY OF THE YUAIPA RIDGE GAUGE EAST OF THE AREA HAD INDICATED OVER THREE QUARTERS OF AN INCH IN 20 MINUTES EARLY THIS AFTERNOON. THUNDERSTORMS WILL MOVE SLOWLY NORTH OR REMAIN NEARLY STATIONARY WITHIN LIGHT SOUTHEAST WINDS. CONTINENTAL TOPICAL AIR MASS WITH PWATS AROUND 1.8 INCH WILL CONTINUE OVER THE AREA AS WELL AS SURGE NORTH THROUGH THE PERIOD. HAVE INCLUDED LOW POPS AS WELL AS THUNDERSTORMS OVER THE EAST HALF OF THE CWA WEDNESDAY AFTERNOON AND EVENING AS WELL AS THURSDAY AFTERNOON AND EVENING. GUIDANCE CONTINUES TO INDICATE A WEAK UPPER CIRCULATION PROPAGATING NORTHWEST ACROSS MEXICO AND THE UPPER DESERT THURSDAY AFTERNOON. .LONG TERM (FRI-MON)...WILL CONTINUE DRY FRI AND THROUGH THE REMAINDER OF THE PERIOD. MARITIME TROPICAL AIR MASS BEGINS TO PUSH EAST AND EXPECT THE THREAT OF THUNDERSTORMS AND SHOWERS WILL DIMINISH. ONSHORE PUSH WILL INCREASE THROUGH THE PERIOD AND THE MARINE LAYER WILL LIKELY RETURN. COASTAL TEMPERATURES WILL LIKELY COOL TO SEVERAL DEGREES BELOW NORMAL FRIDAY THOUGH INLAND TEMPERATURES WILL REMAIN SEVERAL DEGREES ABOVE NORMAL AND LITTLE CHANGE IS EXPECTED THROUGH THE REMAINDER OF THE PERIOD. && .AVIATION...04/1800Z. LOW CONFIDENCE IN THE TAF FORECASTS ON THE COAST SOUTH OF POINT CONCEPTION DUE TO UNCERTAINTY REGARDING THE PRESENCE OF MARINE CLOUDS OVERNIGHT. ELSEWHERE...THERE IS DECENT CONFIDENCE IN THE TAF FORECASTS. LA COUNTY HAS THE LEAST CHANCE OF SEEING MARINE CLOUDS OVERNIGHT DUE TO THE TROPICAL INFLUENCE ASSOCIATED WITH AN UPPER LOW PASSING JUST SOUTH OF THE AREA. KLAX...LOW CONFIDENCE IN THE 18Z TAF. THERE IS A 40 PERCENT CHANCE OF LOW CLOUDS AND FOG WITH IFR CONDITIONS DURING THE NIGHT. KBUR...GOOD CONFIDENCE IN THE 18Z TAF WITH VFR CONDITIONS EXPECTED INTO TUESDAY. && .FIRE WEATHER... SIGNIFICANT SURGE OF MONSOONAL MOISTURE TO OUR SOUTH AND EAST THIS MORNING AS EVIDENT BY THE 1.86 INCH PRECIPITABLE WATER VALUE ON 12Z MIRIMAR SOUNDING. AS EASTERLY WAVE PROPOGATES WESTWARD TODAY THIS SURGE OF MOISTURE IS FORECASTED TO SURGE NORTHWESTWARD INTO OUR FORECAST AREA THIS AFTERNOON AND TONIGHT. WHILE BEST CHANCE OF STORMS TODAY AND TONIGHT WILL OCCUR ACROSS THE MOUNTAINS AND ANTELOPE VALLEY...THERE IS ALSO A SLIGHT CHANCE OF THUNDERSTORMS FOR COASTAL AND VALLEY AREAS SOUTH OF POINT CONCEPTION. AS THE SURGE OF MOISTURE MOVES NORTHWESTARD...THE SMALL CHANCE OF THUNDERSTORMS WILL SPREAD INTO INTERIOR PORTIONS OF SLO COUNTY AND CUYAMA VALLEY ON TUESDAY. OVERALL TREND OF INCREASING MOISTURE WILL BRING BETTER CHANCE OF WETTING RAINS WITH STORMS...WITH EVEN THE POSSIBILITY OF ISOLATED FLASH FLOODING IN THE MOUNTAINS. HOWEVER...COULD INITIALLY SEE SOME ISOLATED DRY LIGHTNING STRIKES ON LEADING EDGE OF MONSOON FRONT AS IT PUSHES UP FROM THE SOUTHEAST. IN FACT...12Z NAM MODEL SOUNDING FOR THE ANTELOPE VALLEY STILL SHOWS INVERTED-V MOISTURE PROFILE FOR THIS AFTERNOON...WITH INCREASING MOISTURE BY LATE AFTERNOON AND TONIGHT. AS A RESULT...BEST THREAT FOR DRY LIGHTNING STRIKES AND GUSTY DOWNBURST WINDS THIS AFTERNOON WILL OCCUR ACROSS THE ANTELOPE VALLEY. SLIGHT CHANCE OF THUNDERSTORMS WILL CONTINUE THROUGH THURSDAY...MAINLY OVER THE MOUNTAINS AND DESERTS...AS THE MOIST SOUTHEAST FLOW ALOFT CONTINUES. && .LOX WATCHES/WARNINGS/ADVISORIES... MARINE WEATHER STATEMENT (SEE LAXMWSLOX). SPECIAL WEATHER STATEMENT (SEE LAXSPSLOX). && PUBLIC...30 AVIATION...SWEET SYNOPSIS...SETO FIRE...GOMBERG WWW.WEATHER.GOV/LOSANGELES
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 600 AM PDT MON JUL 4 2011 CAZ034>041-044>046-051>054-059-087-088-547-548-051300- 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 MON JUL 4 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHWESTERN CALIFORNIA. .DAY ONE... TODAY THERE IS A CHANCE OF THUNDERSTORMS THIS AFTERNOON AND EVENING OVER THE MOUNTAINS AND THE ANTELOPE VALLEY. THERE IS A SLIGHT CHANCE OF THUNDERSTORMS LATE THIS AFTERNOON AND EVENING OVER THE COASTS AND VALLEYS OF LOS ANGELES AND VENTURA COUNTIES. TRIPLE DIGIT HEAT WILL PRODUCE HEAT RELATED HAZARDS THIS AFTERNOON IN THE MOUNTAINS AND DESERTS. PATCHY DENSE FOG WILL CREATE ISOLATED DRIVING HAZARDS EARLY THIS MORNING NEAR THE BEACHES. * SPECIAL WEATHER STATEMENT..SEE WWUS86 KLOX - SPSLOX FOR DETAILS * .DAYS TWO THROUGH SEVEN... TUESDAY THROUGH SUNDAY A SLIGHT CHANCE OF THUNDERSTORMS WILL OCCUR EACH AFTERNOON AND EVENING TUESDAY THROUGH THURSDAY. * SPECIAL WEATHER STATEMENT..SEE WWUS86 KLOX - SPSLOX FOR DETAILS * .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. RORKE
The Los Angeles radar (KVTX), 38 km away, was scanning. The volume nearest the first event began at 21:44 UTC.
3 flash flood, 1 hail. Local standard time, as filed.
Strong thunderstorms produced heavy rainfall and flash flooding across northern Ventura County near the community of Lockwood Valley. Ventura County Fire Department reported significant flooding across Boy Scout Road with between 3 and 5 feet of water across the roadway.
A trained spotter in the Antelope Valley reported large hail with a diameter of one inch.
Strong thunderstorms produced heavy rainfall and flash flooding in northern Ventura County. Ventura County Fire Department reported that about a 10 mile stretch of Lockwood Valley Road was closed due to flash flooding. In some spots, the water was 5 feet deep.
Strong thunderstorms produced heavy rain and flash flooding in the Antelope Valley. A trained spotter reported significant flooding along 263rd street and the Antelope Highway.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2011Every state in 2011This day in weather historyWarnings in California, July 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: 337448, 337457, 337471, 337508.