Alert archive / California / Flash Flood Watches in 2021

Flash Flood Watch 2, NWS Los Angeles, CA

July 26, 2021Los Angeles County, California

NWS Los Angeles, CA issued this flash flood watch at Jul 26, 2021, 1:45 AM PDT for Los Angeles County, California. It took effect at Jul 26, 2021, 2:00 AM PDT. It was in force for 17 hr.

The area

The counties it named.

The facts

Issued: Jul 26, 2021, 1:45 AM PDT (08:45 UTC)
In effect from: Jul 26, 2021, 2:00 AM PDT
Expired: Jul 26, 2021, 7:13 PM PDT
In force: 17 hr
Issued by: NWS Los Angeles, CA
Flood severity: None

County Los Angeles County, CA

The radar

The Santa Ana Mts radar (KSOX), 71 km from the middle of the area, began a volume at 08:48 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.

The nearest sounding before it

San Diego, CA (KNKX), launched 00:00Z, 8.8 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 1166 m above ground
0-6 km bulk shear: 27 kt
0-1 km storm-relative helicity: 36 m²/s²
0-3 km storm-relative helicity: 90 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

536 
WGUS66 KLOX 260845
FFALOX

URGENT - IMMEDIATE BROADCAST REQUESTED
Flood Watch
National Weather Service Los Angeles/Oxnard CA
145 AM PDT Mon Jul 26 2021

CAZ053-054-059-548-261645-
/O.NEW.KLOX.FF.A.0002.210726T0900Z-210727T0300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Ventura County Mountains-Los Angeles County Mountains excluding the
Santa Monica Range-Antelope Valley-Los Angeles County San Gabriel
Valley-
Including the cities of Lancaster, El Monte, East Los Angeles, 
Topatopa Peak, Reyes Peak, West Covina, Alhambra, Falling Springs, 
Pasadena, Pomona, Palmdale, and Whittier
145 AM PDT Mon Jul 26 2021

...FLASH FLOOD WATCH IN EFFECT THROUGH THIS EVENING...

The National Weather Service in Los Angeles/Oxnard has issued a

* Flash Flood Watch for a portion of southwest California, including 
  the following areas, Antelope Valley, Los Angeles County Mountains 
  excluding the Santa Monica Range, Los Angeles County San Gabriel 
  Valley and Ventura County Mountains.

* Through this evening.

* Scattered showers and thunderstorms, some capable of producing 
  heavy downpours with rainfall rates up to an inch per hour are 
  possible.
  Locations most susceptible to flash flooding include those in and 
  below recent burn areas including the Bobcat, Dam, Ranch2, and Lake 
  burn areas. Shallow mud and debris flows capable of producing 
  localized damage are possible in and below these burn areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Flash Flood Watch means that conditions may develop that lead to 
flash flooding. Flash flooding is a very dangerous situation. 
Southern California residents, in or below the recently burned areas 
are urged to take the steps necessary to protect their property. 
Persons in the watch area should remain alert and follow directions 
of emergency preparedness officials. 

More information from the usgs on debris flows and their impacts can 
be found at http://landslides.usgs.gov/research/wildfire/

&&

$$

NWS Los Angeles/Oxnard

2 follow-up statements

348 
WGUS66 KLOX 261644
FFALOX

Flood Watch
National Weather Service Los Angeles/Oxnard CA
944 AM PDT Mon Jul 26 2021

CAZ053-054-059-548-270300-
/O.CON.KLOX.FF.A.0002.000000T0000Z-210727T0300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Ventura County Mountains-Los Angeles County Mountains excluding the
Santa Monica Range-Antelope Valley-Los Angeles County San Gabriel
Valley-
Including the cities of Lancaster, El Monte, East Los Angeles, 
Topatopa Peak, Reyes Peak, West Covina, Alhambra, Falling Springs, 
Pasadena, Pomona, Palmdale, and Whittier
944 AM PDT Mon Jul 26 2021

...FLASH FLOOD WATCH REMAINS IN EFFECT FOR RECENT BURN AREAS IN LOS 
ANGELES AND VENTURA COUNTIES UNTIL 8 PM PDT THIS EVENING...

The Flash Flood Watch continues for

* A portion of southwest California, including the following areas, 
  Antelope Valley, Los Angeles County Mountains excluding the Santa 
  Monica Range, Los Angeles County San Gabriel Valley and Ventura 
  County Mountains.

* Until 8 PM PDT this evening.

* Scattered showers and thunderstorms, some capable of producing 
  heavy downpours with rainfall rates up to an inch per hour are 
  possible.  Locations most susceptible to flash flooding include 
  those in and below recent burn areas including the Bobcat, Dam, 
  Ranch2, and Lake burn areas. Shallow mud and debris flows capable 
  of producing localized damage are possible in and below these burn 
  areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Flash flooding and debris flows will be a particular threat in and 
below the recently burned areas. A flash flood watch means that 
conditions may develop that lead to flash flooding. Flash flooding 
is a very dangerous situation. Southern California residents in or 
below the recently burned areas are urged to take the steps 
necessary to protect their property. Persons in the watch area 
should remain alert and follow directions of emergency preparedness 
officials. More information from the usgs on debris flows and their 
impacts can be found at http://landslides.usgs.gov/research/wildfire/

&&

$$

MJ

179 
WGUS66 KLOX 270213
FFALOX

Flood Watch
National Weather Service Los Angeles/Oxnard CA
713 PM PDT Mon Jul 26 2021

CAZ053-054-059-548-270315-
/O.CAN.KLOX.FF.A.0002.000000T0000Z-210727T0300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Ventura County Mountains-Los Angeles County Mountains excluding the
Santa Monica Range-Antelope Valley-Los Angeles County San Gabriel
Valley-
Including the cities of Lancaster, El Monte, East Los Angeles, 
Topatopa Peak, Reyes Peak, West Covina, Alhambra, Falling Springs, 
Pasadena, Pomona, Palmdale, and Whittier
713 PM PDT Mon Jul 26 2021

...FLASH FLOOD WATCH IS CANCELLED...

The Flash Flood Watch for a portion of southwest California, 
including the following areas, Antelope Valley, Los Angeles County 
Mountains excluding the Santa Monica Range, Los Angeles County San 
Gabriel Valley and Ventura County Mountains has been cancelled.

Flooding is no longer expected to pose a threat this evening. There 
is a chance of thunderstorms developing on Tuesday afternoon across 
the mountains of Los Angeles and Ventura counties, as well as the 
Antelope Valley, which could bring the threat of brief heavy 
downpours and gusty winds.

$$

Gomberg

Nearby

Flash Flood Watches in California, 2021 Every flash flood watch in 2021

Sources

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