Alert archive / California / Flash Flood Warnings in 2017

Flash Flood Warning 21, NWS Los Angeles, CA

September 3, 2017Los Angeles County, California

NWS Los Angeles, CA issued this flash flood warning at Sep 3, 2017, 3:15 PM PDT for Los Angeles County, California. It was in force for 3 hr. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued
Sep 3, 2017, 3:15 PM PDT (22:15 UTC)
Expired
Sep 3, 2017, 6:15 PM PDT
In force
3 hr
Issued by
NWS Los Angeles, CA
Area
Storm-based polygon
Flood severity
None

County Los Angeles County, CA

The radar

The Edwards AFB radar (KEYX), 68 km from the middle of the area, began a volume at 22:17 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 12:00Z, 10.3 hours before the alert went out and 219 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, San Diego, CA at 12:00Z on 2017-09-03Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 108 joules per kilogram.LCLLFCEL10008507005003002001001 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, San Diego, CA at 12:00Z on 2017-09-03The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -28 square meters per square second.193958Sfc1 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
108 J/kg
Mixed-layer CIN
-184 J/kg
Mixed-layer LCL
1874 m above ground
0-6 km bulk shear
12 kt
0-1 km storm-relative helicity
-28 m²/s²
0-3 km storm-relative helicity
5 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

995 
WGUS56 KLOX 032215
FFWLOX
CAC037-040115-
/O.NEW.KLOX.FF.W.0021.170903T2215Z-170904T0115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service OXNARD CA
315 PM PDT SUN SEP 3 2017

The National Weather Service in OXNARD has issued a

* Flash Flood Warning for...
  the Antelope Valley in Northeastern Los Angeles County in 
  southwestern California...

* Until 615 PM PDT

* At 309 PM PDT, Doppler radar indicated a line of strong 
  thunderstorms over the eastern Antelope Valley, training
  from Lake Los Angeles to Palmdale. Estimated rainfall rates
  up to one inch per hour have been observed.

* Some locations that will experience flooding include...
  Lake Los Angeles...Lancaster...Palmdale...Highway 14...
  and Saddleback Butte State Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.

&&

LAT...LON 3455 11824 3462 11834 3472 11816 3479 11767
      3458 11767

$$

Gomberg/Bruno
2 follow-up statements
886 
WGUS76 KLOX 032254
FFSLOX

Flash Flood Statement
National Weather Service OXNARD CA
354 PM PDT SUN SEP 3 2017

CAC037-040115-
/O.CON.KLOX.FF.W.0021.000000T0000Z-170904T0115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Los Angeles CA-
354 PM PDT SUN SEP 3 2017

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 615 PM PDT FOR
THE ANTELOPE VALLEY IN NORTHEASTERN LOS ANGELES COUNTY...

At 347 PM PDT, Doppler radar indicated the focus of heaviest rainfall has
shifted northward on a line extending from Saddleback Butte to Lancaster.
Radar has estimated rainfall rates up to one inch per hour with this
storm. In addition, there have been reports of wind gusts with 50 to
60 mph with this storm, which has produced downed power lines near
Lancaster. 

Some locations that could experience flooding include...
Lake Los Angeles, Lancaster, and Saddleback Butte State Park, as well
as portions of Highway 14.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.

&&

LAT...LON 3455 11824 3462 11834 3472 11816 3479 11767
      3458 11767

$$

Gomberg/Hall
296 
WGUS76 KLOX 040112
FFSLOX

Flash Flood Statement
National Weather Service OXNARD CA
612 PM PDT SUN SEP 3 2017

CAC037-040120-
/O.EXP.KLOX.FF.W.0021.000000T0000Z-170904T0115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Los Angeles CA-
612 PM PDT SUN SEP 3 2017

...THE FLASH FLOOD WARNING FOR THE ANTELOPE VALLEY IN NORTHEASTERN
LOS ANGELES COUNTY WILL
EXPIRE AT 615 PM PDT...

The heavy rain has ended, and flooding is no longer expected to pose
an immediate threat. A Flash Flood Watch remains in effect through 10 pm
as there is still the potential for additional thunderstorms through
the evening hours.

LAT...LON 3455 11824 3462 11834 3472 11816 3479 11767
      3458 11767

$$

Gomberg

The office that day

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

IssuedProductOfficeCountiesLasted
Sep 2, 9:34 PM PDTWind AdvisoryLOX24 hr
Sep 3, 6:13 AM PDTSmall Craft AdvisoryLOX8 hr
Sep 3, 12:01 PM PDTSpecial Weather StatementLOXLos Angeles59 min
Sep 3, 1:07 PM PDTFlash Flood WatchLOXLos Angeles8 hr
Sep 3, 1:31 PM PDTSpecial Weather StatementLOXVentura44 min
Sep 3, 2:08 PM PDTFlash Flood WarningLOXSanta Barbara, Ventura2 hr
Sep 3, 2:38 PM PDTSpecial Weather StatementLOXSanta Barbara52 min
Sep 3, 2:55 PM PDTSpecial Weather StatementLOX80 min
Sep 3, 2:59 PM PDTSpecial Marine WarningLOX46 min
Sep 3, 3:38 PM PDTSevere Thunderstorm WarningLOXSan Luis Obispo, Santa Barbara52 min
Sep 3, 3:58 PM PDTFlash Flood WarningLOXSan Luis Obispo, Santa Barbara4 hr
Sep 3, 3:58 PM PDTSpecial Weather StatementLOXSanta Barbara62 min
Sep 3, 4:09 PM PDTSpecial Marine WarningLOX66 min

Nearby

Flash Flood Warnings in California, 2017Every flash flood warning in 2017

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.