Alert archive / California / Flash Flood Warnings in 2021

Flash Flood Warning 234, NWS Phoenix, AZ

August 31, 2021La Paz County, Arizona; Imperial County, Riverside County, California

NWS Phoenix, AZ issued this flash flood warning at Aug 31, 2021, 1:24 PM MST for La Paz County, Arizona; Imperial County, Riverside County, California. It was in force for 13 hr. 3 reports 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 31, 2021, 1:24 PM MST (20:24 UTC)
Expired: Sep 1, 2021, 2:30 AM MST
In force: 13 hr
Issued by: NWS Phoenix, AZ
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

Counties La Paz County, AZ, Imperial County, CA, Riverside County, CA

The radar

The Yuma radar (KYUX), 96 km from the middle of the area, began a volume at 20:25 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 31, 1:59 PM MST	FLASH FLOOD	Palo Verde, CA	CORRECTS PREVIOUS FLASH FLOOD REPORT FROM PALO VERDE. SR-78/PALO VERDE RD IS WASHED OUT DUE TO FLASH FLOODING.
Aug 31, 2:47 PM MST	FLASH FLOOD	11 Ssw Palo Verde, CA	VEHICLE SWEPT OFF HIGHWAY 78 DOWN MILPITAS WASH WITH OCCUPANTS STILL INSIDE ACCORDING TO CHP.
Aug 31, 2:47 PM MST	FLASH FLOOD	11 Ssw Palo Verde, CA	* 2 FATAL * *UPDATES PREVIOUS REPORT* PER LOCAL MEDIA REPORT, THE BODIES OF THE TWO MISSING OCCUPANTS OF A VEHICLE THAT WAS SWEPT OFF HIGHWAY 78 DOWN MILPITAS WASH ON AUGUST 31ST WERE RECOVERED BY SEARCH-AND-RESCUE TEAMS AS OF SEPTEMBER 6TH.

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

The nearest sounding before it

Yuma Prvg Ground, AZ (K1Y7), launched 12:00Z, 8.4 hours before the alert went out and 101 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: 302 J/kg
Mixed-layer CIN: -242 J/kg
Mixed-layer LCL: 1872 m above ground
0-6 km bulk shear: 14 kt
0-1 km storm-relative helicity: 66 m²/s²
0-3 km storm-relative helicity: 99 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.7

Open this sounding in Storm Lab

The text

As transmitted.

333 
WGUS55 KPSR 312024
FFWPSR
AZC012-CAC025-065-010430-
/O.NEW.KPSR.FF.W.0234.210831T2024Z-210901T0430Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

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

The National Weather Service in Phoenix has issued a

* Flash Flood Warning for...
  Western La Paz County in west central Arizona...
  Northeastern Imperial County in southeastern California...
  Riverside County in southern California...

* Until 930 PM MST Tuesday /930 PM PDT Tuesday/.

* At 124 PM MST /124 PM PDT/, Doppler radar indicated thunderstorms 
  producing heavy rain across the warned area. Between 0.5 and 1.5 
  inches of rain have fallen. Additional rainfall amounts of 0.5 to 
  1.5 inches are possible in the warned area. Flash flooding is 
  ongoing or expected to begin shortly, particularly where washes 
  cross Highway 78.

  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...
  Palo Verde and Cibola.

This includes the following highways...
	CA Route 78 between mile markers 62 and 71.

This includes the following streams and drainages...
  Crazy Woman Wash, Vinagre Wash, Gould Wash, Lopez Wash, Clip Wash, 
  Hart Mine Wash, Colorado River and Milpitas Wash.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3348 11488 3354 11484 3356 11478 3354 11470
      3348 11465 3343 11463 3335 11461 3325 11462
      3318 11465 3316 11470 3316 11475 3317 11481
      3321 11486 3332 11493 3341 11491

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

$$

Hirsch

3 follow-up statements

972 
WGUS75 KPSR 312124
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
224 PM MST Tue Aug 31 2021

AZC012-CAC025-065-010430-
/O.CON.KPSR.FF.W.0234.000000T0000Z-210901T0430Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
La Paz AZ-Imperial CA-Riverside CA-
224 PM MST Tue Aug 31 2021 /224 PM PDT Tue Aug 31 2021/

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 930 PM MST/930 PM 
PDT/ THIS EVENING FOR WESTERN LA PAZ, NORTHEASTERN IMPERIAL AND 
RIVERSIDE COUNTIES...

At 224 PM MST /224 PM PDT/, Doppler radar indicated thunderstorms 
producing heavy rain near Highway 78. Between 1 and 3 inches of rain 
have fallen. Additional rainfall amounts of 0.5 to 2 inches 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...
  Palo Verde and Cibola.

This includes the following highways...
	CA Route 78 between mile markers 62 and 71.

This includes the following streams and drainages...
  Crazy Woman Wash, Vinagre Wash, Gould Wash, Lopez Wash, Clip Wash, 
  Hart Mine Wash, Colorado River and Milpitas Wash.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be aware of your surroundings and do not drive on flooded roads.

&&

LAT...LON 3348 11488 3354 11484 3356 11478 3354 11470
      3348 11465 3343 11463 3335 11461 3325 11462
      3318 11465 3316 11470 3316 11475 3317 11481
      3321 11486 3332 11493 3341 11491

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

$$

Hirsch

801 
WGUS55 KPSR 010417
FFWPSR
AZC012-CAC025-065-010930-
/O.EXT.KPSR.FF.W.0234.000000T0000Z-210901T0930Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

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

The National Weather Service in Phoenix has extended the

* Flash Flood Warning for...
  Western La Paz County in west central Arizona...
  Northeastern Imperial County in southeastern California...
  Riverside County in southern California...

* Until 230 AM MST /230 AM PDT/.

* At 917 PM MST /917 PM PDT/, Doppler radar indicated thunderstorms 
  produced heavy rain along Highway 78 in eastern Imperial County. 
  Up to 4 inches of rain have fallen. Flash flooding is 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...
  Palo Verde and Cibola.

This includes the following highways...
	CA Route 78 between mile markers 62 and 71.

This includes the following streams and drainages...
  Crazy Woman Wash, Vinagre Wash, Gould Wash, Lopez Wash, Clip Wash, 
  Hart Mine Wash, Colorado River and Milpitas Wash.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be aware of your surroundings and do not drive on flooded roads.

&&

LAT...LON 3348 11488 3354 11484 3356 11478 3354 11470
      3348 11465 3343 11463 3335 11461 3325 11462
      3318 11465 3316 11470 3316 11475 3317 11481
      3321 11486 3332 11493 3341 11491

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

$$

CK

843 
WGUS75 KPSR 010923
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
223 AM MST Wed Sep 1 2021

AZC012-CAC025-065-010933-
/O.EXP.KPSR.FF.W.0234.000000T0000Z-210901T0930Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
La Paz AZ-Imperial CA-Riverside CA-
223 AM MST Wed Sep 1 2021 /223 AM PDT Wed Sep 1 2021/

...FLASH FLOOD WARNING WILL EXPIRE AT 230 AM MST/230 AM PDT/ EARLY 
THIS MORNING FOR WESTERN LA PAZ, NORTHEASTERN IMPERIAL AND RIVERSIDE 
COUNTIES...

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

LAT...LON 3348 11488 3354 11484 3356 11478 3354 11470
      3348 11465 3343 11463 3335 11461 3325 11462
      3318 11465 3316 11470 3316 11475 3317 11481
      3321 11486 3332 11493 3341 11491

$$

Iniguez

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 30, 8:18 PM MST	Special Weather Statement	PSR		27 min
Aug 30, 9:06 PM MST	Flash Flood Warning Considerable damage threat	PSR	La Paz	5 hr
Aug 30, 10:59 PM MST	Areal Flood Advisory	PSR	Maricopa, Pinal	4 hr
Aug 30, 11:17 PM MST	Areal Flood Advisory	PSR	La Paz	3 hr
Aug 31, 12:06 AM MST	Special Weather Statement	PSR	Maricopa	39 min
Aug 31, 12:24 AM MST	Areal Flood Advisory	PSR	Maricopa	3 hr
Aug 31, 12:50 AM MST	Flash Flood Warning Considerable damage threat	PSR	Maricopa	4 hr
Aug 31, 2:55 AM MST	Areal Flood Advisory	PSR	Maricopa	3 hr
Aug 31, 5:52 AM MST	Areal Flood Advisory	PSR	Maricopa	3 hr
Aug 31, 12:39 PM MST	Special Weather Statement	PSR		66 min
Aug 31, 1:13 PM MST	Areal Flood Advisory	PSR	La Paz	6 hr
Aug 31, 1:35 PM MST	Special Weather Statement	PSR		70 min
Aug 31, 4:55 PM MST	Flash Flood Warning Considerable damage threat	PSR	Gila, Maricopa	3 hr
Aug 30, 5:14 PM MST	Flash Flood Warning Considerable damage threat	PSR	Imperial, Riverside	4 hr
Aug 30, 6:49 PM MST	Areal Flood Advisory	PSR	Imperial	3 hr
Aug 30, 7:37 PM MST	Special Weather Statement	PSR	Riverside	23 min
Aug 30, 7:52 PM MST	Areal Flood Advisory	PSR	Riverside	23 min
Aug 30, 8:13 PM MST	Flash Flood Warning Considerable damage threat	PSR	Riverside	50 min
Aug 31, 5:46 AM MST	Areal Flood Advisory	PSR	Imperial	3 hr
Aug 31, 3:48 PM MST	Special Weather Statement	PSR	Imperial	87 min
Aug 31, 4:15 PM MST	Special Weather Statement	PSR	Imperial	90 min
Aug 31, 4:30 PM MST	Severe Thunderstorm Warning	PSR	Imperial	75 min

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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.