Alert archive / California / Flash Flood Warnings in 2021

Flash Flood Warning 232, NWS Phoenix, AZ

August 30, 2021Riverside County, California; La Paz County, Arizona

NWS Phoenix, AZ issued this flash flood warning at Aug 30, 2021, 9:06 PM PDT for Riverside County, California; La Paz County, Arizona. It was in force for 5 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: Aug 30, 2021, 9:06 PM PDT (04:06 UTC)
Expired: Aug 31, 2021, 2:15 AM PDT
In force: 5 hr
Issued by: NWS Phoenix, AZ
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

Counties La Paz County, AZ, Riverside County, CA

The radar

The Yuma radar (KYUX), 149 km from the middle of the area, began a volume at 04:07 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

Yuma Prvg Ground, AZ (K1Y7), launched 00:00Z, 4.1 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: 761 J/kg
Mixed-layer CIN: -65 J/kg
Mixed-layer LCL: 2897 m above ground
0-6 km bulk shear: 12 kt
0-1 km storm-relative helicity: 34 m²/s²
0-3 km storm-relative helicity: 51 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

068 
WGUS55 KPSR 310406
FFWPSR
AZC012-CAC065-310815-
/O.NEW.KPSR.FF.W.0232.210831T0406Z-210831T0815Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

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

The National Weather Service in Phoenix has issued a

* Flash Flood Warning for...
  West Central La Paz County in west central Arizona...
  Riverside County in southern California...

* Until 115 AM MST /115 AM PDT/.

* At 906 PM MST /906 PM PDT/, Doppler radar indicated thunderstorms 
  producing heavy rain across the warned area. Between 1 and 2 
  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...
  Blythe, Ehrenberg and East Blythe.

This includes the following highways...
	AZ Interstate 10 between mile markers 1 and 4.
	CA Interstate 10 between mile markers 153 and 156.
	CA Route 95 near mile marker 1...and
	between mile markers 10 and 18.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

&&

LAT...LON 3402 11461 3401 11447 3398 11448 3387 11451
      3378 11443 3366 11443 3360 11447 3359 11459
      3373 11458 3377 11455 3386 11465 3390 11467

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

$$

18

3 follow-up statements

571 
WGUS75 KPSR 310527
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
1027 PM MST Mon Aug 30 2021

AZC012-CAC065-310815-
/O.CON.KPSR.FF.W.0232.000000T0000Z-210831T0815Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
La Paz AZ-Riverside CA-
1027 PM MST Mon Aug 30 2021 /1027 PM PDT Mon Aug 30 2021/

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 115 AM MST/115 AM 
PDT/ TUESDAY FOR WEST CENTRAL LA PAZ AND RIVERSIDE COUNTIES...

At 1027 PM MST /1027 PM PDT/, Doppler radar indicated thunderstorms 
have produced heavy rain across the warned area. Between 1 and 2 
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...
  Blythe, Ehrenberg and East Blythe.

This includes the following highways...
	AZ Interstate 10 between mile markers 1 and 4.
	CA Interstate 10 between mile markers 154 and 156.
	CA Route 95 near mile marker 1...and
	between mile markers 10 and 18.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

&&

LAT...LON 3402 11461 3401 11447 3398 11448 3387 11451
      3378 11443 3366 11443 3360 11447 3359 11459
      3373 11458 3377 11455 3386 11465 3390 11467

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

$$

18

303 
WGUS55 KPSR 310806
FFWPSR
AZC012-CAC065-310915-
/O.EXT.KPSR.FF.W.0232.000000T0000Z-210831T0915Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Phoenix AZ
106 AM MST Tue Aug 31 2021

The National Weather Service in Phoenix has extended the

* Flash Flood Warning for...
  West Central La Paz County in west central Arizona...
  Riverside County in southern California...

* Until 215 AM MST /215 AM PDT/.

* At 106 AM MST /106 AM PDT/, Doppler radar indicated additional 
  shower activity within the warned area. Between 1 and 2 inches of 
  rain have fallen. Flash flooding is likely ongoing.

  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...
  Blythe, Ehrenberg and East Blythe.

This includes the following highways...
	AZ Interstate 10 between mile markers 1 and 4.
	CA Interstate 10 between mile markers 154 and 156.
	CA Route 95 near mile marker 1...and
	between mile markers 10 and 18.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

&&

LAT...LON 3402 11461 3401 11447 3398 11448 3387 11451
      3378 11443 3366 11443 3360 11447 3359 11459
      3373 11458 3377 11455 3386 11465 3390 11467

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

$$

AJ

628 
WGUS75 KPSR 310913
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
213 AM MST Tue Aug 31 2021

AZC012-CAC065-310923-
/O.EXP.KPSR.FF.W.0232.000000T0000Z-210831T0915Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
La Paz AZ-Riverside CA-
213 AM MST Tue Aug 31 2021 /213 AM PDT Tue Aug 31 2021/

...FLASH FLOOD WARNING WILL EXPIRE AT 215 AM MST/215 AM PDT/ EARLY 
THIS MORNING FOR WEST CENTRAL LA PAZ AND RIVERSIDE COUNTIES...

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 3402 11461 3401 11447 3398 11448 3387 11451
      3378 11443 3366 11443 3360 11447 3359 11459
      3373 11458 3377 11455 3386 11465 3390 11467

$$

AJ

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, 8:13 PM PDT	Flash Flood Warning Considerable damage threat	PSR	Riverside	50 min
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
Aug 30, 8:18 PM PDT	Special Weather Statement	PSR		27 min
Aug 30, 10:59 PM PDT	Areal Flood Advisory	PSR	Maricopa, Pinal	4 hr
Aug 30, 11:17 PM PDT	Areal Flood Advisory	PSR	La Paz	3 hr
Aug 31, 12:06 AM PDT	Special Weather Statement	PSR	Maricopa	39 min
Aug 31, 12:24 AM PDT	Areal Flood Advisory	PSR	Maricopa	3 hr
Aug 31, 12:50 AM PDT	Flash Flood Warning Considerable damage threat	PSR	Maricopa	4 hr
Aug 31, 2:55 AM PDT	Areal Flood Advisory	PSR	Maricopa	3 hr
Aug 31, 5:52 AM PDT	Areal Flood Advisory	PSR	Maricopa	3 hr
Aug 31, 12:39 PM PDT	Special Weather Statement	PSR		66 min
Aug 31, 1:35 PM PDT	Special Weather Statement	PSR		70 min
Aug 31, 4:55 PM PDT	Flash Flood Warning Considerable damage threat	PSR	Gila, Maricopa	3 hr

Nearby

Flash Flood Warnings in California, 2021 Flash Flood Warnings in Arizona, 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.