Alert archive / California / Flash Flood Warnings in 2011

Flash Flood Warning 3, NWS Los Angeles, CA

March 20, 2011Los Angeles County, California

NWS Los Angeles, CA issued this flash flood warning at Mar 20, 2011, 5:47 PM PDT for Los Angeles County, California. It was in force for 118 min. 2 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued
Mar 20, 2011, 5:47 PM PDT (00:47 UTC)
Expired
Mar 20, 2011, 7:45 PM PDT
In force
118 min
Issued by
NWS Los Angeles, CA
Area
Storm-based polygon
Flood severity
None

County Los Angeles County, CA

The radar

The Los Angeles radar (KVTX), 60 km from the middle of the area, began a volume at 00:47 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

What was reported inside it

TimeReportWhereRemark
Mar 20, 6:14 PM PDTFLASH FLOOD5 S Woodland Hills, CAMUD AND DEBRIS FLOWING DOWN STREET. AT LEAST FOUR TO FIVE VEHICLES STUCK IN STUCK IN FLOWING WATER. ONE BEING SWEPT AWAY IN FLOOD WATERS.
Mar 20, 6:50 PM PDTFLASH FLOOD6 S Woodland Hills, CAMUDSLIDE AND FLOODING OCCURRING REQUIRING ROAD CLOSURE.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Vandenberg AFB, CA (KVBG), launched 00:00Z, 0.8 hours before the alert went out and 184 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Vandenberg AFB, CA at 00:00Z on 2011-03-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Vandenberg AFB, CA at 00:00Z on 2011-03-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 6 square meters per square second.1939587897117136Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
652 m above ground
0-6 km bulk shear
73 kt
0-1 km storm-relative helicity
6 m²/s²
0-3 km storm-relative helicity
34 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

760 
WGUS56 KLOX 210047
FFWLOX
CAC037-210245-
/O.NEW.KLOX.FF.W.0003.110321T0047Z-110321T0245Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE OXNARD CA
547 PM PDT SUN MAR 20 2011

THE NATIONAL WEATHER SERVICE IN OXNARD HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  SOUTHWESTERN LOS ANGELES COUNTY IN SOUTHWEST CALIFORNIA...

* UNTIL 745 PM PDT

* AT 536 PM PDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED 
  WIDESPREAD HEAVY RAIN ACROSS WESTERN LOS ANGELES COUNTY. A LINE
  OF INTENSE SHOWERS EXTENDED FROM MALIBU NORTHWARD TO WOODLAND
  HILLS AND CALABASAS. RAINFALL RATES OVER 1 INCH PER HOUR HAVE BEEN
  REPORTED AT SEVERAL LOCATIONS IN MALIBU AND THE ADJACENT FOOTHILLS.
  THIS RAIN WILL PRODUCE SIGNIFICANT FLASH FLOODING AND FLOODING OF
  ROADWAYS IN WESTERN LOS ANGELES COUNTY INCLUDING THE 101 FREEWAY
  FROM CALABASAS THROUGH RESEDA AND ON PACIFIC COAST HIGHWAY FROM    
  MALIBU TO PACIFIC PALISADES. ROCK SLIDES AND MUD SLIDES ARE LIKELY
  TO AFFECT PACIFIC COAST HIGHWAY AND CANYON ROADS THROUGH THE SANTA
  MONICA MOUNTAINS.


* LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO VAN NUYS...
  MALIBU...SANTA MONICA...WOODLAND HILLS AND AGOURA HILLS

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FLASH FLOOD WARNING MEANS THAT FLOODING IS IMMINENT OR OCCURRING.
IF YOU ARE IN THE WARNING AREA MOVE TO HIGHER GROUND IMMEDIATELY.
RESIDENTS LIVING ALONG STREAMS AND CREEKS SHOULD TAKE IMMEDIATE
PRECAUTIONS TO PROTECT LIFE AND PROPERTY. DO NOT ATTEMPT TO CROSS
SWIFTLY FLOWING WATERS OR WATERS OF UNKNOWN DEPTH BY FOOT OR BY
AUTOMOBILE.

LAT...LON 3400 11849 3403 11856 3403 11867 3402 11870
      3403 11875 3401 11878 3416 11880 3417 11867
      3424 11867 3425 11863 3430 11864 3433 11853
      3424 11842

$$

BRUNO
1 follow-up statement
146 
WGUS76 KLOX 210151
FFSLOX

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE OXNARD CA
651 PM PDT SUN MAR 20 2011

CAC037-210245-
/O.CON.KLOX.FF.W.0003.000000T0000Z-110321T0245Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
LOS ANGELES CA-
651 PM PDT SUN MAR 20 2011

...A FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 745 PM PDT FOR WEST
CENTRAL LOS ANGELES COUNTY...

AT 642 PM PDT...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO
INDICATE VERY HEAVY RAIN ACROSS WESTERN LOS ANGELES COUNTY. A LINE
OF INTENSE SHOWERS WAS STILL AFFECTING THE AREA FROM MALIBU NORTHWARD
TO WOODLAND HILLS. RAINFALL RATES WERE STILL OVER 1 INCH PER HOUR WITH
THIS LINE. THE TORRENTIAL RAIN WILL PRODUCE SIGNIFICANT FLASH FLOODING
AND FLOODING OF ROADWAYS IN WESTERN LOS ANGELES COUNTY INCLUDING THE
101 FREEWAY FROM CALABASAS THROUGH RESEDA AND PACIFIC COAST HIGHWAY
FROM  MALIBU TO PACIFIC PALISADES UNTIL 745 PM PDT. ROCK SLIDES AND
MUD SLIDES ARE LIKELY TO AFFECT PACIFIC COAST HIGHWAY AND CANYON ROADS
THROUGH THE SANTA MONICA MOUNTAINS.

LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO MALIBU...
WOODLAND HILLS AND TOPANGA.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FLASH FLOOD WARNING MEANS THAT FLOODING IS IMMINENT OR OCCURRING.
IF YOU ARE IN THE WARNING AREA MOVE TO HIGHER GROUND IMMEDIATELY.
RESIDENTS LIVING ALONG STREAMS AND CREEKS SHOULD TAKE IMMEDIATE
PRECAUTIONS TO PROTECT LIFE AND PROPERTY. DO NOT ATTEMPT TO CROSS
SWIFTLY FLOWING WATERS OR WATERS OF UNKNOWN DEPTH BY FOOT OR BY
AUTOMOBILE.

&&

LAT...LON 3400 11849 3403 11856 3403 11867 3402 11870
      3403 11875 3401 11878 3416 11880 3417 11867
      3424 11867 3425 11863 3430 11864 3433 11853
      3424 11842

$$

BRUNO/ASR

The office that day

Everything else NWS Los Angeles, CA issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Mar 20, 5:51 PM PDTAreal Flood AdvisoryLOXSan Luis Obispo, Santa Barbara3 hr
Mar 20, 6:05 PM PDTAreal Flood AdvisoryLOXSan Luis Obispo, Santa Barbara3 hr
Mar 20, 7:33 PM PDTFlash Flood WarningLOXLos Angeles87 min
Mar 21, 11:00 AM PDTSpecial Marine WarningLOX25 min

Nearby

Flash Flood Warnings in California, 2011Every flash flood warning in 2011

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.