Alert archive / California / Flash Flood Warnings in 2021

Flash Flood Warning 231, NWS Phoenix, AZ

August 30, 2021Riverside County, California

NWS Phoenix, AZ issued this flash flood warning at Aug 30, 2021, 8:13 PM PDT for Riverside County, California. It was in force for 50 min. 1 report 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: Aug 30, 2021, 8:13 PM PDT (03:13 UTC)
Expired: Aug 30, 2021, 9:03 PM PDT
In force: 50 min
Issued by: NWS Phoenix, AZ
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

County Riverside County, CA

The radar

The San Diego radar (KNKX), 128 km from the middle of the area, began a volume at 03:13 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

Time	Report	Where	Remark
Aug 30, 8:29 PM PDT	FLASH FLOOD	10 Ne Desert Shores, CA	*DELAYED REPORT* SEA VIEW WAY CLOSED DUE TO FLOODING. TIME ESTIMATED FROM RADAR.

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

The nearest sounding before it

San Diego, CA (KNKX), launched 00:00Z, 3.2 hours before the alert went out and 148 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: 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.

596 
WGUS55 KPSR 310313
FFWPSR
CAC065-310715-
/O.NEW.KPSR.FF.W.0231.210831T0313Z-210831T0715Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Phoenix AZ
813 PM PDT Mon Aug 30 2021

The National Weather Service in Phoenix has issued a

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

* Until 1215 AM PDT.

* At 813 PM PDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1 and 1.5 inches of 
  rain have fallen. Additional rainfall amounts of 0.5 to 1 inch are 
  possible in the warned area. 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...
  North Shore.

This includes the following highways...
	CA Interstate 10 between mile markers 74 and 81.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3346 11587 3351 11593 3352 11595 3369 11595
      3368 11579

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

$$

INS

2 follow-up statements

096 
WGUS75 KPSR 310350
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
850 PM PDT Mon Aug 30 2021

CAC065-310715-
/O.CON.KPSR.FF.W.0231.000000T0000Z-210831T0715Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Riverside CA-
850 PM PDT Mon Aug 30 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 1215 AM PDT TUESDAY 
FOR RIVERSIDE COUNTY...

At 850 PM PDT, Doppler radar indicated thunderstorms producing heavy 
rain across the warned area. Between 1 and 1.5 inches of rain have 
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...
  North Shore.

This includes the following highways...
	CA Interstate 10 between mile markers 74 and 81.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3346 11587 3351 11593 3352 11595 3369 11595
      3368 11579

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

$$

INS

792 
WGUS75 KPSR 310403
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
903 PM PDT Mon Aug 30 2021

CAC065-310413-
/O.CAN.KPSR.FF.W.0231.000000T0000Z-210831T0715Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Riverside CA-
903 PM PDT Mon Aug 30 2021

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

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

LAT...LON 3346 11587 3351 11593 3352 11595 3369 11595
      3368 11579

$$

18

The office that day

Everything else NWS Phoenix, AZ issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 30, 5:14 PM PDT	Flash Flood Warning Considerable damage threat	PSR	Imperial, Riverside	4 hr
Aug 30, 6:49 PM PDT	Areal Flood Advisory	PSR	Imperial	3 hr
Aug 30, 7:37 PM PDT	Special Weather Statement	PSR	Riverside	23 min
Aug 30, 7:52 PM PDT	Areal Flood Advisory	PSR	Riverside	23 min
Aug 30, 9:06 PM PDT	Flash Flood Warning Considerable damage threat	PSR	Riverside	5 hr
Aug 31, 5:46 AM PDT	Areal Flood Advisory	PSR	Imperial	3 hr
Aug 31, 1:13 PM PDT	Areal Flood Advisory	PSR	Imperial, Riverside	6 hr
Aug 31, 1:24 PM PDT	Flash Flood Warning Considerable damage threat	PSR	Imperial, Riverside	13 hr
Aug 31, 3:48 PM PDT	Special Weather Statement	PSR	Imperial	87 min
Aug 31, 4:15 PM PDT	Special Weather Statement	PSR	Imperial	90 min
Aug 31, 4:30 PM PDT	Severe Thunderstorm Warning	PSR	Imperial	75 min

Nearby

Flash Flood Warnings in California, 2021 Every 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.