At the end of the month, another round of monsoonal flow developed across Southern California. Strong thunderstorms, producing heavy rainfall and flash flooding, were reported across sections of the area.
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.
At the end of the month, another round of monsoonal flow developed across Southern California. Strong thunderstorms, producing heavy rainfall and flash flooding, were reported across sections of the area.
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 30, 1:48 PM PST, 2 hours 2 minutes earlier.
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 248 PM PDT SAT JUL 30 2011 .SYNOPSIS... A MOIST SOUTHEAST FLOW ALOFT AROUND A HIGH PRESSURE SYSTEM TO THE EAST WILL STEER MONSOONAL MOISTURE INTO THE AREA THROUGH THE WEEKEND. A DRIER SOUTHWESTERLY FLOW ALOFT BEGINS TUESDAY AS HIGH PRESSURE MOVES EAST. TEMPERATURES WILL REMAIN WARM THROUGH THE PERIOD. && .SHORT TERM (TONIGHT-TUESDAY)... CONVECTION IS BEGINNING TO FIRE OVER THE AREA THIS AFTERNOON AS A MOIST SOUTHEAST FLOW CONTINUES TO DEVELOP. THE MOISTURE IN THE FLOW PATTERN IS PROVIDED BY A RIDGE OF HIGH PRESSURE OVER THE FRONT RANGE OF THE ROCKIES. A FEATURE OVER NORTHERN BAJA CALIFORNIA WILL BE MONITORED CLOSELY THROUGHOUT TONIGHT FOR ANY DEVELOPMENT. WITH WINDS ALOFT REMAINING LIGHT...MID-LEVEL MOISTURE IN PLACE...AND THE ATMOSPHERE ALREADY UNSTABLE...A FLASH FLOOD WATCH CONTINUES FOR THE LOS ANGELES AND VENTURA COUNTY MOUNTAINS AND THE ANTELOPE VALLEY. WITH MODEL SOLUTIONS INDICATING 850-700 MB MIXING RATIOS NEAR 10 G/KG AND 500 MB VORTICITY ADVECTION OCCURRING...THERE IS A DEFINITE POSSIBILITY THAT THE CONVECTION WILL LINGER INTO THIS EVENING AND SPILL OVER THE COASTAL AND VALLEY AREAS. SLIGHT CHANCE POPS REMAIN THROUGH TONIGHT TO ACCOUNT FOR THIS POSSIBILITY. WITH THE FEATURE MOVING NORTH...CLOUD COVER WILL BE PROBLEMATIC FOR TONIGHT AND SUNDAY. THE MIDDLE LEVEL MOISTURE STREAMING NORTH OVER THE AREA WILL BE PROBLEMATIC FOR THE MARINE LAYER TONIGHT SOUTH OF POINT CONCEPTION. THE PACKAGE LEAVES ANY MENTION OF MARINE LAYER OUT SOUTH OF POINT CONCEPTION...AND KEEP MENTION NORTH OF POINT CONCEPTION. HOWEVER IF THE FEATURE MOVES FURTHER WEST...THE CENTRAL COAST COULD BE AFFECTED AND THE MARINE LAYER COULD BECOME MORE LIMITED. THE CLOUDS WILL LIKELY CUT INTO DAYTIME HIGH TEMPERATURES ALSO ON SUNDAY. TEMPERATURES FOR SUNDAY WERE COOLED A BIT ACROSS THE AREA TAKING THIS INTO ACCOUNT. BUT...IT EASILY COULD MORE CLOUDY THAN PARTLY CLOUDY. WHILE A FLOOD THREAT IS HIGH TODAY AND SUNDAY...THERE IS SOME CONCERN FOR A THREAT OF ISOLATED STRONG THUNDERSTORMS COULD DEVELOP ACROSS THE MOUNTAINS AND DESERTS ON SUNDAY. NAM BUFR TIME HEIGHT SECTIONS INDICATE DECENT OMEGA VALUES EXTENDING UP INTO -10 CELSIUS ISOTHERM ON SUNDAY. ANY THUNDERSTORMS THAT DEVELOP ON SUNDAY COULD BE MORE HAIL CONTAMINATED. TEMPERATURES SHOULD WARM TO NEAR CLIMATOLOGICAL VALUES ON MONDAY AND TUESDAY AS THE SOUTHWEST FLOW ALOFT FINALLY TAKES HOLD OVER THE AREA. SOME SORT OF MARINE LAYER SHOULD DEVELOP NEAR THE COAST...AND INTRUSION INTO THE LOWER VALLEYS IS POSSIBLE...ESPECIALLY THE SAN GABRIEL AND SANTA YNEZ VALLEYS. .LONG TERM (WEDNESDAY-SATURDAY)... SOUTHWEST FLOW ALOFT OVER THE AREA THROUGH LATE WEEK SHOULD KEEP TEMPERATURES AROUND CLIMATOLOGICAL VALUES FOR THE LONG TERM PERIOD AND SOME SORT MARINE LAYER SHOULD OCCUR ESPECIALLY NEAR THE COAST. OTHERWISE...DRY AND SEASONAL CONDITIONS SHOULD BE EXPECTED FOR LATE WEEK. && .AVIATION...30/1800Z. MID/UPPER LEVEL TROUGH OF LOW PRESSURE IN THE VICINITY OF CENTRAL BAJA WILL MOVE OVER THE AREA BY 31/18Z. MODERATE AND RELATIVELY MOIST UPPER LEVEL SOUTH WINDS WILL BECOME MODERATE AND DRIER SOUTHWEST AFTER 31/19Z. LIGHT AND RELATIVELY MOIST MID LEVEL SOUTHEAST WINDS WILL BECOME MODERATE SOUTH 31/12Z THEN BECOME DRIER AND LIGHT SOUTHWEST BY 31/20Z. ISOLATED THUNDERSTORMS THROUGH THE THOUGH DIMINISHING CHANCE AFTER 31/18Z. THUNDERSTORM TOPS WILL AVERAGE 40KFT AND MOVE SLOWLY NORTH THROUGH 31/12Z THEN MOVE NORTHWEST AROUND 15KT. MARINE LAYER TOP WAS AROUND 1.5KFT THIS MORNING AND WILL DIFFER BY MINUS .2KFT AND BECOME DISORGANIZED SUNDAY MORNING. WEAK/MODERATE ONSHORE PRESSURE GRADIENT WILL BECOME WEAK AFTER 31/04Z. KLAX...CHANCE CIGS 011 THROUGH 30/19Z THEN CHANCE CIGS 010 BY 31/03Z. CHANCE CIGS 009 BETWEEN 31/05-31/16Z. OTHERWISE BKN180-200 30/19-31/20Z. KBUR...CHANCE BKN150 BY 31/11Z. VIRTUALLY CERTAIN - 95-100% VERY LIKELY - 80-95% LIKELY - 60-80% CHANCE - 30-60% VERY UNLIKELY - 20% OR LESS && .LOX WATCHES/WARNINGS/ADVISORIES... FLASH FLOOD WATCH (SEE LAXFFALOX). SMALL CRAFT ADVISORY (SEE LAXMWWLOX). && PUBLIC...HALL AVIATION...30 SYNOPSIS...HOFFER/HALL WWW.WEATHER.GOV/LOSANGELES
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 600 AM PDT SAT JUL 30 2011 CAZ034>041-044>046-051>054-059-087-088-547-548-311300- 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 SAT JUL 30 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHWESTERN CALIFORNIA. .DAY ONE... TODAY SCATTERED THUNDERSTORMS CAN BE EXPECTED ACROSS THE MOUNTAINS OF LOS ANGELES AND VENTURA COUNTIES TODAY THROUGH THIS EVENING...THEN A SLIGHT CHANCE OF THUNDERSTORMS OVERNIGHT. THERE WILL BE THE POTENTIAL FOR HEAVY DOWNPOURS WITH HOURLY RAINFALL RATES OVER ONE INCH AT TIMES. AREAS MOST SUSCEPTIBLE TO POTENTIAL FLOODING WILL BE AREAS NEAR LOCKWOOD VALLEY...THE SAN GABRIEL MOUNTAINS AND BIG ROCK CREEK AND LITTLEROCK CREEK ACROSS THE ANTELOPE VALLEY. THERE WILL BE ISOLATED SHOWERS ACROSS THE COAST AND VALLEYS OF LOS ANGELES AND VENTURA COUNTY AS WELL CAUSING SLICK ROADWAYS. THERE COULD BE A FEW THUNDERSTORMS ACROSS THE INNER COASTAL WATERS THIS AFTERNOON THROUGH THIS EVENING AS WELL. * FLOOD WATCH................SEE WGUS66 KLOX - FFALOX FOR DETAILS * * SPECIAL WEATHER STATEMENT..SEE WWUS86 KLOX - SPSLOX FOR DETAILS * .DAYS TWO THROUGH SEVEN... SUNDAY THROUGH FRIDAY SUNDAY WILL BRING ANOTHER DAY OF THUNDERSTORM ACTIVITY TO THE MOUNTAINS AND ANTELOPE VALLEY. THERE WILL BE THE POTENTIAL OF FLASH FLOODING ONCE AGAIN FOR THE SAME AREAS MENTIONED ABOVE. SANTA BARBARA COUNTY MOUNTAINS MIGHT NEED TO BE ADDED TO THE FLASH FLOOD WATCH FOR SUNDAY. THERE WILL BE A SLIGHT CHANCE OF THUNDERSTORMS FOR THE MOUNTAINS OF LOS ANGELES AND VENTURA COUNTY AS WELL AS THE ANTELOPE VALLEY ON MONDAY...BUT STORMS SHOULD MORE ISOLATED IN NATURE. * FLOOD WATCH................SEE WGUS66 KLOX - FFALOX FOR DETAILS * .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. KAPLAN
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE OXNARD CA 308 PM PDT SAT JUL 30 2011 CAZ059-302230- ANTELOPE VALLEY CA- 308 PM PDT SAT JUL 30 2011 ...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN LOS ANGELES COUNTY UNTIL 330 PM PDT... AT 304 PM PDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM 10 MILES SOUTH OF EDWARDS AFB...OR 18 MILES EAST OF LANCASTER...MOVING NORTH AT 10 MPH. HAIL UP TO ONE-HALF INCH IN DIAMETER AND WIND GUSTS UP TO 50 MPH ARE EXPECTED WITH THIS STORM...ALONG WITH HEAVY RAIN AND FREQUENT DANGEROUS LIGHTNING. * LOCATIONS IMPACTED INCLUDE... THE NORTHEAST PORTION OF THE ANTELOPE VALLEY IN LOS ANGELES COUNTY NEAR EAST AVENUE E AND 140TH ST EAST... IF THREATENING WEATHER APPROACHES YOUR AREA...TAKE SHELTER IN A STURDY BUILDING. LAT...LON 3470 11792 3483 11798 3482 11773 3475 11771 TIME...MOT...LOC 2206Z 172DEG 9KT 3478 11788 HALL
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 414 PM PDT SAT JUL 30 2011 CAZ034>041-044>046-051>054-059-087-088-547-548-311400- 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- 414 PM PDT SAT JUL 30 2011 ...THREAT OF MONSOONAL THUNDERSTORMS ACROSS SOUTHWEST CALIFORNIA THROUGH MONDAY... A HIGH PRESSURE SYSTEM CENTERED OVER THE FRONT RANGE OF THE ROCKY MOUNTAINS WILL CONTINUE TO PROVIDE A MOIST SOUTHEAST FLOW ALOFT. THE FLOW PATTERN WILL CONTINUE TO STEER MONSOONAL MOISTURE AND INSTABILITY INTO SOUTHERN CALIFORNIA THROUGH MONDAY. THE LEADING EDGE OF THIS MOISTURE WILL BRING A CHANCE OF THUNDERSTORMS TO THE MOUNTAINS OF LOS ANGELES AND VENTURA COUNTIES AS WELL AS THE ANTELOPE VALLEY THROUGH THE WEEKEND. IN ADDITION...AN UPPER LEVEL DISTURBANCE WILL BRING A SLIGHT CHANCE OF THUNDERSTORMS TO COASTAL AND VALLEY AREAS SOUTH OF POINT CONCEPTION THROUGH TONIGHT. BY MONDAY...AN UPPER LEVEL LOW PRESSURE SYSTEM OFF THE COAST WILL BEGIN TO BRING DRIER SOUTHWEST FLOW INTO MUCH OF THE FORECAST AREA...BUT A SLIGHT CHANCE OF THUNDERSTORMS WILL CONTINUE FOR THE LOS ANGELES AND VENTURA COUNTY MOUNTAINS AS WELL AS THE ANTELOPE VALLEY. THE WEATHER PATTERN HAS THE POTENTIAL TO BRING SIGNIFICANT MONSOONAL MOISTURE INTO SOUTHWEST CALIFORNIA. AS A RESULT...ANY THUNDERSTORMS THAT DEVELOP COULD BRING HEAVY RAINFALL...ESPECIALLY IN THE MOUNTAINS AND ANTELOPE VALLEY. SINCE THE UPPER LEVEL WINDS WILL BE RELATIVELY WEAK THROUGH THE WEEKEND...STORMS WILL LIKELY BE SLOW MOVING...INCREASING THE THREAT FOR FLASH FLOODING. A FLASH FLOOD WATCH IS IN EFFECT THROUGH SUNDAY EVENING FOR THE MOUNTAINS OF LOS ANGELES AND VENTURA COUNTIES...AS WELL AS THE ANTELOPE VALLEY. THE FLASH FLOOD WATCH MAY NEED TO BE EXPANDED INTO THE SANTA BARBARA COUNTY MOUNTAINS ON SUNDAY. SOME THUNDERSTORMS COULD PRODUCE GUSTY WINDS...HAIL...AND DANGEROUS CLOUD TO GROUND LIGHTNING. PEOPLE PLANNING OUTDOOR ACTIVITIES IN THE MOUNTAINS AND DESERTS THIS WEEKEND SHOULD CLOSELY MONITOR THE LATEST NATIONAL WEATHER SERVICE STATEMENTS...AND BE READY TO TAKE ACTION IF DANGEROUS WEATHER CONDITIONS DEVELOP. HALL
The national radar mosaic for the moment the first event began.
2 flash flood. Local standard time, as filed.
Strong thunderstorms produced heavy rainfall and flash flooding near the community of Crystalaire. A trained spotter reported flash flooding along Largo Vista Road with water over 1 foot deep.
Strong thunderstorms produced heavy rainfall and flash flooding in the foothills of the Antelope Valley. California Highway Patrol reported flash flooding at the intersection of Big Pines Highway and Los Angeles County Road 4.
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: 337536, 337540.