Alert archive / California / Flash Flood Warnings in 2021

Flash Flood Warning 11, NWS San Diego, CA

August 30, 2021Riverside County, California

NWS San Diego, CA issued this flash flood warning at Aug 30, 2021, 8:18 PM PDT for Riverside County, California. It was in force for 37 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued
Aug 30, 2021, 8:18 PM PDT (03:18 UTC)
Expired
Aug 30, 2021, 8:55 PM PDT
In force
37 min
Issued by
NWS San Diego, CA
Area
Storm-based polygon
Damage threat
Considerable
Flood severity
None

County Riverside County, CA

The radar

The San Diego radar (KNKX), 116 km from the middle of the area, began a volume at 03:20 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, 3.3 hours before the alert went out and 136 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 00:00Z on 2021-08-31Temperature 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, San Diego, CA at 00:00Z on 2021-08-31The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 9 square meters per square second.1939Sfc1 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
1693 m above ground
0-6 km bulk shear
13 kt
0-1 km storm-relative helicity
9 m²/s²
0-3 km storm-relative helicity
21 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

880 
WGUS56 KSGX 310318
FFWSGX
CAC065-310630-
/O.NEW.KSGX.FF.W.0011.210831T0318Z-210831T0630Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service San Diego CA
818 PM PDT Mon Aug 30 2021

The National Weather Service in San Diego has issued a

* Flash Flood Warning for...
  Riverside County in southern California...

* Until 1130 PM PDT.

* At 818 PM PDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 0.5 and 1 inch of rain 
  has fallen. Flash flooding is ongoing or expected to begin shortly.

  HAZARD...Life threatening flash flooding. Thunderstorms
           producing flash flooding.

  SOURCE...Radar.

  IMPACT...Life threatening flash flooding of creeks and streams,
           urban areas, highways, streets and underpasses.

* Some locations that will experience flash flooding include...
  Coachella, Thermal and Mecca.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3350 11607 3350 11608 3370 11610 3371 11595
      3352 11595 3351 11598 3352 11599 3352 11600
      3352 11602 3352 11603 3352 11605 3352 11606
      3351 11605 3351 11606 3351 11607

FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

SS
1 follow-up statement
711 
WGUS76 KSGX 310355
FFSSGX

Flash Flood Statement
National Weather Service San Diego CA
855 PM PDT Mon Aug 30 2021

CAC065-310405-
/O.CAN.KSGX.FF.W.0011.000000T0000Z-210831T0630Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Riverside CA-
855 PM PDT Mon Aug 30 2021

...FLASH FLOOD WARNING IS CANCELLED FOR RIVERSIDE COUNTY...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat. Please continue to heed remaining road closures.

LAT...LON 3350 11607 3350 11608 3370 11610 3371 11595
      3352 11595 3351 11598 3352 11599 3352 11600
      3352 11602 3352 11603 3352 11605 3352 11606
      3351 11605 3351 11606 3351 11607

$$

SS

The office that day

Everything else NWS San Diego, CA issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 30, 7:58 PM PDTSpecial Weather StatementSGXRiverside47 min
Aug 31, 3:30 PM PDTSpecial Weather StatementSGXSan Diego45 min
Aug 31, 4:13 PM PDTSevere Thunderstorm WarningSGXSan Diego62 min
Aug 31, 4:55 PM PDTSpecial Weather StatementSGX65 min

Nearby

Flash Flood Warnings in California, 2021Every flash flood warning 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.