Alert archive / California / Flash Flood Warnings in 2021

Flash Flood Warning 104, NWS Phoenix, AZ

July 28, 2021Riverside County, California

NWS Phoenix, AZ issued this flash flood warning at Jul 28, 2021, 2:42 PM PDT for Riverside County, California. It was in force for 2 hr. 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: Jul 28, 2021, 2:42 PM PDT (21:42 UTC)
Expired: Jul 28, 2021, 5:00 PM PDT
In force: 2 hr
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), 158 km from the middle of the area, began a volume at 21:44 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 28, 2:59 PM PDT	FLASH FLOOD	11 N Jtnp-Cottonwood Vi, CA	* DELAYED REPORT * VEHICLES TRAVELING ALONG PINTO BASIN RD. BETWEEN FRIED LIVER WASH AND TURKEY FLATS WERE FORCED TO TURN AROUND DUE TO SEVERAL INCHES OF FAST-MOVING WATER OVER THE ROADWAY FROM WASHES.

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 12:00Z, 9.7 hours before the alert went out and 177 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: 1533 m above ground
0-6 km bulk shear: 21 kt
0-1 km storm-relative helicity: 24 m²/s²
0-3 km storm-relative helicity: 55 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

635 
WGUS55 KPSR 282142
FFWPSR
CAC065-290000-
/O.NEW.KPSR.FF.W.0104.210728T2142Z-210729T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Phoenix AZ
242 PM PDT Wed Jul 28 2021

The National Weather Service in Phoenix has issued a

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

* Until 500 PM PDT.

* At 242 PM PDT, Doppler radar indicated thunderstorms producing 
  heavy rain in Joshua Tree National Park. Between 1 and 2 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...
  mainly rural areas of Riverside County

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3404 11590 3397 11568 3388 11568 3375 11577
      3380 11593 3395 11612 3403 11597 3404 11596
      3404 11592

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

$$

SDB

2 follow-up statements

286 
WGUS75 KPSR 282244
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
344 PM PDT Wed Jul 28 2021

CAC065-290000-
/O.CON.KPSR.FF.W.0104.000000T0000Z-210729T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Riverside CA-
344 PM PDT Wed Jul 28 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 5 PM PDT THIS 
AFTERNOON FOR RIVERSIDE COUNTY...

At 344 PM PDT, Doppler radar indicated thunderstorms producing heavy 
rain in Joshua Tree National Park. Between 1 and 2 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. This
         includes Pinto Wash.

Some locations that will experience flash flooding include...
  mainly rural areas of Riverside County

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 3404 11590 3397 11568 3388 11568 3375 11577
      3380 11593 3395 11612 3403 11597 3404 11596
      3404 11592

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

$$

Iniguez

933 
WGUS75 KPSR 282355
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
455 PM PDT Wed Jul 28 2021

CAC065-290005-
/O.EXP.KPSR.FF.W.0104.000000T0000Z-210729T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Riverside CA-
455 PM PDT Wed Jul 28 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 5 PM PDT THIS AFTERNOON 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 3404 11590 3397 11568 3388 11568 3375 11577
      3380 11593 3395 11612 3403 11597 3404 11596
      3404 11592

$$

Iniguez

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 28, 11:49 AM PDT	Areal Flood Advisory	PSR	Riverside	3 hr
Jul 28, 1:00 PM PDT	Areal Flood Advisory	PSR	Riverside, San Bernardino	20 min
Jul 28, 1:20 PM PDT	Flash Flood Warning Considerable damage threat	PSR	Riverside, San Bernardino	3 hr
Jul 28, 2:00 PM PDT	Areal Flood Advisory	PSR	Riverside	42 min
Jul 28, 4:07 PM PDT	Areal Flood Advisory	PSR	Riverside	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.