A surge of monsoonal moisture brought another round of strong thunderstorms and flash flooding to the Antelope Valley. Heavy rain and flash flooding was reported across Leona Valley and near Quartz Hill High School.
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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 surge of monsoonal moisture brought another round of strong thunderstorms and flash flooding to the Antelope Valley. Heavy rain and flash flooding was reported across Leona Valley and near Quartz Hill High School.
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 Aug 26, 4:10 PM PST, 1 hour 15 minutes earlier.
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 510 PM PDT MON AUG 26 2013 UPDATED AVIATION SECTION .SYNOPSIS... A SURGE OF MOISTURE FROM THE REMNANTS OF ONCE TROPICAL STORM IVO WILL BRING A THREAT OF THUNDERSTORMS TO PARTS OF THE AREA STARTING MONDAY AFTERNOON...WITH THE THREAT LIKELY LASTING THROUGH THE END OF THE WEEK. COASTAL AREAS WILL LIKELY SEE A SIGNIFICANT WARM UP EARLY THIS WEEK...AS ONSHORE FLOW WEAKENS. A WEAK TROUGH APPROACHING FROM THE NORTHWEST NEXT WEEKEND SHOULD BRING AN END TO THE THUNDERSTORM ACTIVITY...ALONG WITH SLIGHTLY COOLER WEATHER. && .SHORT TERM (TODAY-THU)...PLUME OF OLD IVO MOISTURE STILL STREAMING NORTH INTO SO CAL, THOUGH SO FAR THE DEEPER MOISTURE HAS REMAINED SOUTH AND EAST AND CONVECTION HAS BEEN MINIMAL. MODELS CONTINUE TO ADVERTISE A FAIR AMOUNT OF MID LEVEL MOISTURE MOVING INTO EASTERN HALF OF THE FORECAST AREA TONIGHT INTO TUESDAY AND WHILE THE MOISTURE MAY IN FACT MOVE THAT FAR WEST I'M HAVING DOUBTS THAT THE THICK CLOUD COVER WILL ACCOMPANY THAT MOISTURE. WAS NOT VERY IMPRESSED WITH STABILITY PARAMETERS OVERNIGHT AND SO FAR NOT SEEING ANY REAL UPPER LEVEL KICKERS TO FIRE STORMS OFF WITHOUT DAYTIME HEATING. MODEL SOUNDINGS OVER COASTAL AREAS NOT SHOWING MUCH CAPE AND LAPSE RATES ARE MARGINAL AT BEST. SO THIS DOESN'T HAVE THE SIGNS OF A CLASSIC OVERNIGHT THUNDERSTORM OUTBREAK BUT CAN'T RULE IT COMPLETELY OUT EITHER. ISOLATED SPRINKLES OR LIGHT SHOWERS MAY ACTUALLY BE A SLIGHTLY BETTER BET ESPECIALLY IF THAT PLUME DOES SHIFT FARTHER NORTH AND WEST OVER OUR AREA. SO I'VE TRIMMED BACK CLOUD COVERAGE TONIGHT BUT LEFT POPS MOSTLY THE WAY THEY WERE, IE CHANCE OR SLIGHT CHANCE ACROSS LA/VENTURA COUNTIES TONIGHT AND EARLY TUESDAY. THE FLASH FLOOD WATCH FOR THE LA MTNS AND AV HAS BEEN EXTENDED TO INCLUDE TUESDAY AND ALSO VENTURA COUNTY WAS ADDED FOR TUESDAY. STABILITY PARAMETERS LOOK MORE IMPRESSIVE TUESDAY AFTERNOON THAN TODAY FOR THE MOUNTAINS AND AV. TEMPS WILL REMAIN WARM AND MUGGY MOST OF THE WEEK, THOUGH INCREASING ONSHORE FLOW SHOULD BRING TEMPS DOWN A FEW DEGREES TUESDAY AND WEDNESDAY CLOSER TO NORMAL LEVELS. MUGGINESS SHOULD DECREASE LATE TUESDAY AND WEDNESDAY AS MOISTURE SURGE WANES, THEN INCREASE AGAIN THURSDAY AS ANOTHER LITTLE BURST OF MONSOON MOISTURE MOVES IN. STILL ENOUGH MOISTURE AND INSTABILITY WEDNESDAY FOR A SLIGHT CHANCE OF AFTERNOON CONVECTION OVER THE MTNS AND AV WITH A LITTLE BETTER CHANCE THU. MODELS INDICATE GRADIENTS TRENDING OFFSHORE THU AS WELL SO THU COULD BE A SIMILAR DAY AS TODAY IN TERMS OF HIGH TEMPS AND MUGGINESS. .LONG TERM (FRI-MON)...FAIRLY BIG DIFFERENCES NOTED IN THE MEDIUM RANGE MODELS TODAY. BOTH THE GFS AND ECMWF SHOW A PRETTY STRONG WAVE MOVING INTO THE CO RIVER VALLEY FRIDAY MORNING BUT LIKELY TOO FAR EAST FOR OUR AREA. THE ECMWF SHOWS ANOTHER WAVE WITH PRETTY GOOD MOISTURE SATURDAY MORNING WITH THAT MOISTURE LINGERING THROUGH THE WEEKEND. THE GFS IS SHARPLY DIFFERENT WITH THE WEEKEND PATTERN, SHOWING THE WEST COAST TROF EASILY PUSHING THE MOISTURE EAST OF OUR AREA WITH MUCH DRIER SOUTHWEST FLOW ALOFT AND STABLE CONDITIONS ACROSS OUR AREA. ALL MODELS SHOW COOLING FOR THE AREA CONTINUING THROUGH EARLY NEXT WEEK. && .AVIATION...27/0010Z. AT COASTAL TERMINALS...THERE IS A CHANCE OF VLIFR TO IFR CONDITIONS...WITH THE BEST CHANCE AT COASTAL TERMINALS NORTH OF POINT CONCEPTION. OTHERWISE...VFR CONDITIONS WILL PERSIST AT ALL OTHER TERMINALS. THERE IS CHANCE OF SHOWERS AND THUNDERSTORMS...WITH THE BEST CHANCE THIS EVENING. KLAX...THERE IS A 30 PERCENT CHANCE OF VLIFR TO IFR CONDITIONS BETWEEN 10Z AND 15Z. THERE IS A 20 PERCENT OF SHOWERS AND THUNDERSTORMS BETWEEN 06Z AND 12Z. KBUR...VFR CONDITIONS ARE EXPECTED THROUGHOUT THE PERIOD. THERE IS A 20 PERCENT OF SHOWERS AND THUNDERSTORMS BETWEEN 06Z AND 12Z. && .LOX WATCHES/WARNINGS/ADVISORIES... FLOOD WATCH (SEE LAXFFALOX). SMALL CRAFT ADVISORY (SEE LAXMWWLOX). MARINE WEATHER STATEMENT (SEE LAXMWSLOX). && PUBLIC...MW AVIATION...30 SYNOPSIS...SWEET WWW.WEATHER.GOV/LOSANGELES
HAZARDOUS WEATHER OUTLOOK...UPDATED NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 120 PM PDT MON AUG 26 2013 CAZ034>041-044>046-051>054-059-087-088-547-548-271300- 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- 120 PM PDT MON AUG 26 2013 THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHWESTERN CALIFORNIA. .DAY ONE... TODAY AND TONIGHT THERE IS A CHANCE OF SHOWERS AND THUNDERSTORMS ACROSS THE MOUNTAINS OF LOS ANGELES COUNTY AND THE ANTELOPE VALLEY THIS AFTERNOON AND EVENING. A FLASH FLOOD WATCH REMAINS IN EFFECT FOR THEPOTENTIAL FOR HEAVY RAINFALL AND FLASH FLOODING IN THESE AREAS...PARTICULARLY ACROSS EASTERN SECTIONS. THERE IS A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS ACROSS ALL OF LOS ANGELES AND VENTURA COUNTIES LATE TONIGHT...WITH THE POTENTIAL FOR HEAVY RAINFALL IN SOME AREAS. * FLOOD WATCH................SEE WGUS66 KLOX - FFALOX FOR DETAILS * * MARINE WEATHER STATEMENT...SEE FZUS76 KLOX - MWSLOX FOR DETAILS * .DAYS TWO THROUGH SEVEN... TUESDAY THROUGH SUNDAY THERE IS A CHANCE OF SHOWERS AND THUNDERSTORMS MUCH OF THE REGION TUESDAY...WITH THE POTENTIAL FOR HEAVY RAINFALL IN THE MOUNTAINS AND ANTELOPE VALLEY. THERE WILL BE A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS IN THE MOUNTAINS OF LOS ANGELES AND VENTURA COUNTIES AND THE ANTELOPE VALLEY DURING THE AFTERNOON AND EVENING HOURS WEDNESDAY THROUGH SATURDAY. * FLOOD WATCH................SEE WGUS66 KLOX - FFALOX FOR DETAILS * * MARINE WEATHER STATEMENT...SEE FZUS76 KLOX - MWSLOX FOR DETAILS * .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. MW
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OXNARD CA
536 PM PDT MON AUG 26 2013
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0529 PM HEAVY RAIN 2 SSW ACTON 34.46N 118.20W
08/26/2013 M1.85 INCH LOS ANGELES CA MESONET
1.85 INCHES OF RAINFALL IN 39 MINUTES AT ACTON PUMP
STATION.
&&
HALLPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OXNARD CA
612 PM PDT MON AUG 26 2013
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0558 PM FLASH FLOOD 2 SSW ACTON 34.46N 118.20W
08/26/2013 LOS ANGELES CA BROADCAST MEDIA
WATER ACROSS CROWN VALLEY RD AND COUNTRY WAY SOUTH OF
ACTON...ELEVATION 2600 FEET.
&&
HALLPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OXNARD CA
625 PM PDT MON AUG 26 2013
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0625 PM FLASH FLOOD 1 WSW ACTON 34.48N 118.20W
08/26/2013 LOS ANGELES CA TRAINED SPOTTER
HEAVY RAINFALL OCCURRED WITH FLASH FLOODING IN ACTON.
POWER OUTAGE CURRENTLY.
&&
HALLThe Edwards AFB radar (KEYX), 83 km away, was scanning. The volume nearest the first event began at 01:25 UTC.
1 flash flood. Local standard time, as filed.
Trained spotters reported widespread flash flooding across the communities of Quartz Hill and Leona Valley. The area around 60th Street and Quartz Hill High School experienced flash flooding as well as the area around 90th Street West and Elizabeth Lake Road in Leona Valley.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2013Every state in 2013This day in weather historyWarnings in California, August 2013
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: 467100.