Alert archive / California / Flash Flood Warnings in 2021

Flash Flood Warning 246, NWS Phoenix, AZ

September 9, 2021Riverside County, California

NWS Phoenix, AZ issued this flash flood warning at Sep 9, 2021, 5:47 PM PDT for Riverside County, California. It was in force for 3 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: Sep 9, 2021, 5:47 PM PDT (00:47 UTC)
Expired: Sep 9, 2021, 8:32 PM PDT
In force: 3 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 00:49 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

San Diego, CA (KNKX), launched 00:00Z, 0.8 hours before the alert went out and 178 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: 2385 m above ground
0-6 km bulk shear: 27 kt
0-1 km storm-relative helicity: 7 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.

430 
WGUS55 KPSR 100047
FFWPSR
CAC065-100445-
/O.NEW.KPSR.FF.W.0246.210910T0047Z-210910T0445Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Phoenix AZ
547 PM PDT Thu Sep 9 2021

The National Weather Service in Phoenix has issued a

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

* Until 945 PM PDT.

* At 547 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 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...
  Joshua Tree National Park and the Cottonwood Visitor Center.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3370 11583 3391 11589 3395 11584 3397 11561
      3378 11550 3372 11556

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

$$

INS

2 follow-up statements

097 
WGUS75 KPSR 100113
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
613 PM PDT Thu Sep 9 2021

CAC065-100445-
/O.CON.KPSR.FF.W.0246.000000T0000Z-210910T0445Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Riverside CA-
613 PM PDT Thu Sep 9 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 945 PM PDT THIS 
EVENING FOR RIVERSIDE COUNTY...

At 613 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.

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...
  Cottonwood Visitor Center.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3370 11583 3391 11589 3395 11584 3397 11561
      3378 11550 3372 11556

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

$$

JS

300 
WGUS75 KPSR 100332
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
832 PM PDT Thu Sep 9 2021

CAC065-100342-
/O.CAN.KPSR.FF.W.0246.000000T0000Z-210910T0445Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Riverside CA-
832 PM PDT Thu Sep 9 2021

...FLASH FLOOD WARNING IS CANCELLED 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 3370 11583 3391 11589 3395 11584 3397 11561
      3378 11550 3372 11556

$$

JS

The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 9, 5:14 PM PDT	Special Weather Statement	PSR	Riverside	31 min
Sep 9, 5:52 PM PDT	Special Weather Statement	PSR	Riverside	23 min
Sep 10, 2:19 AM PDT	Excessive Heat Warning	PSR	Imperial, Riverside, San Bernardino	4 days
Sep 10, 4:03 PM PDT	Severe Thunderstorm Warning	PSR	Imperial	42 min
Sep 10, 4:22 PM PDT	Flash Flood Warning Considerable damage threat	PSR	Imperial	5 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.