Alert archive / California / Flash Flood Warnings in 2021

Flash Flood Warning 96, NWS Phoenix, AZ

July 25, 2021Riverside County, California

NWS Phoenix, AZ issued this flash flood warning at Jul 25, 2021, 6:35 PM PDT for Riverside County, California. It was in force for 4 hr. 2 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: Jul 25, 2021, 6:35 PM PDT (01:35 UTC)
Expired: Jul 25, 2021, 10:45 PM PDT
In force: 4 hr
Issued by: NWS Phoenix, AZ
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

County Riverside County, CA

The radar

The Yuma radar (KYUX), 159 km from the middle of the area, began a volume at 01:37 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
Jul 25, 6:38 PM PDT	FLASH FLOOD	Desert Center, CA	TRAINED SPOTTER REPORTED 3-4 INCHES OF FLOWING WATER OVER THE ROADWAY.
Jul 25, 7:12 PM PDT	FLASH FLOOD	9 Ne Desert Center, CA	MULTIPLE REPORTS OF MUD AND DEBRIS COVERING RICE RD (177) IN VARIOUS SPOTS NEAR THE DESERT LILY SANCTUARY.

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, 1.6 hours before the alert went out and 200 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: 1166 m above ground
0-6 km bulk shear: 27 kt
0-1 km storm-relative helicity: 36 m²/s²
0-3 km storm-relative helicity: 90 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

198 
WGUS55 KPSR 260135
FFWPSR
CAC065-260545-
/O.NEW.KPSR.FF.W.0096.210726T0135Z-210726T0545Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Phoenix AZ
635 PM PDT Sun Jul 25 2021

The National Weather Service in Phoenix has issued a

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

* Until 1045 PM PDT.

* At 635 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 up 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...
  Desert Center and Eagle Mtn.

This includes the following highways...
	CA Route 177 between mile markers 1 and 17.
	CA Interstate 10 between mile markers 101 and 110.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

In hilly terrain there are hundreds of low water crossings which are 
potentially dangerous in heavy rain. Do not attempt to cross flooded 
roads. Find an alternate route.

&&

LAT...LON 3393 11528 3392 11526 3389 11522 3388 11522
      3382 11522 3374 11529 3369 11532 3363 11533
      3362 11534 3361 11536 3363 11541 3365 11544
      3371 11549 3376 11556 3380 11558 3381 11558
      3384 11557 3385 11556 3389 11551 3390 11545

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

$$

Iniguez

2 follow-up statements

927 
WGUS75 KPSR 260424 RRC
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
924 PM PDT Sun Jul 25 2021

CAC065-260545-
/O.CON.KPSR.FF.W.0096.000000T0000Z-210726T0545Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Riverside CA-
924 PM PDT Sun Jul 25 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 1045 PM PDT THIS 
EVENING FOR RIVERSIDE COUNTY...

At 924 PM PDT, Doppler radar indicated thunderstorms producing heavy 
rain across the warned area. Between 0.5 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...
  Desert Center and Eagle Mtn.

This includes the following highways...
	CA Route 177 between mile markers 1 and 17.
	CA Interstate 10 between mile markers 101 and 110.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

In hilly terrain there are hundreds of low water crossings which are 
potentially dangerous in heavy rain. Do not attempt to cross flooded 
roads. Find an alternate route.

&&

LAT...LON 3393 11528 3392 11526 3389 11522 3388 11522
      3382 11522 3374 11529 3369 11532 3363 11533
      3362 11534 3361 11536 3363 11541 3365 11544
      3371 11549 3376 11556 3380 11558 3381 11558
      3384 11557 3385 11556 3389 11551 3390 11545

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

$$

Iniguez

704 
WGUS75 KPSR 260542
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
1042 PM PDT Sun Jul 25 2021

CAC065-260552-
/O.EXP.KPSR.FF.W.0096.000000T0000Z-210726T0545Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Riverside CA-
1042 PM PDT Sun Jul 25 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 1045 PM PDT THIS EVENING 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 3393 11528 3392 11526 3389 11522 3388 11522
      3382 11522 3374 11529 3369 11532 3363 11533
      3362 11534 3361 11536 3363 11541 3365 11544
      3371 11549 3376 11556 3380 11558 3381 11558
      3384 11557 3385 11556 3389 11551 3390 11545

$$

Iniguez

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 25, 6:13 PM PDT	Flash Flood Warning Considerable damage threat	PSR	Riverside	4 hr
Jul 25, 6:54 PM PDT	Flash Flood Warning Considerable damage threat	PSR	Imperial	4 hr
Jul 25, 8:08 PM PDT	Flash Flood Warning Considerable damage threat	PSR	Imperial	4 hr
Jul 26, 1:52 AM PDT	Areal Flood Advisory	PSR	Imperial	3 hr
Jul 26, 3:36 AM PDT	Flash Flood Warning Considerable damage threat	PSR	Riverside	6 hr
Jul 26, 6:49 AM PDT	Areal Flood Advisory	PSR	Riverside	3 hr
Jul 26, 8:01 AM PDT	Areal Flood Advisory	PSR	Riverside, San Bernardino	3 hr

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.