Alert archive / California / Flash Flood Warnings in 2021

Flash Flood Warning 124, NWS Phoenix, AZ

July 31, 2021Riverside County, California

NWS Phoenix, AZ issued this flash flood warning at Jul 31, 2021, 4:48 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
Jul 31, 2021, 4:48 PM PDT (23:48 UTC)
Expired
Jul 31, 2021, 7:43 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), 149 km from the middle of the area, began a volume at 23:49 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 12:00Z, 11.8 hours before the alert went out and 169 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-pSkew-T log-p diagram, San Diego, CA at 12:00Z on 2021-07-31Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, San Diego, CA at 12:00Z on 2021-07-31The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 8 square meters per square second.1939Sfc1 km3 km6 km9 kmRMLM
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
2352 m above ground
0-6 km bulk shear
4 kt
0-1 km storm-relative helicity
8 m²/s²
0-3 km storm-relative helicity
26 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

190 
WGUS55 KPSR 312348
FFWPSR
CAC065-010345-
/O.NEW.KPSR.FF.W.0124.210731T2348Z-210801T0345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Phoenix AZ
448 PM PDT Sat Jul 31 2021

The National Weather Service in Phoenix has issued a

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

* Until 845 PM PDT.

* At 448 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 0.5 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... 
  Porcupine Wash in Joshua Tree National Park

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3374 11586 3388 11602 3397 11595 3392 11578
      3377 11573

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

$$

INS
2 follow-up statements
076 
WGUS75 KPSR 010059
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
559 PM PDT Sat Jul 31 2021

CAC065-010345-
/O.CON.KPSR.FF.W.0124.000000T0000Z-210801T0345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Riverside CA-
559 PM PDT Sat Jul 31 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 845 PM PDT THIS 
EVENING FOR RIVERSIDE COUNTY...

At 559 PM PDT, Doppler radar indicated thunderstorms producing heavy 
rain across the warned area. Between 1 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... 
Porcupine Wash in Joshua Tree National Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3374 11586 3388 11602 3397 11595 3392 11578
      3377 11573

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

$$

INS
401 
WGUS75 KPSR 010243
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
743 PM PDT Sat Jul 31 2021

CAC065-010253-
/O.CAN.KPSR.FF.W.0124.000000T0000Z-210801T0345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Riverside CA-
743 PM PDT Sat Jul 31 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 3374 11586 3388 11602 3397 11595 3392 11578
      3377 11573

$$

INS

The office that day

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

IssuedProductOfficeCountiesLasted
Jul 30, 5:04 PM PDTDust Storm AdvisoryPSRImperial41 min
Jul 30, 5:18 PM PDTSpecial Weather StatementPSRImperial72 min
Jul 30, 5:20 PM PDTSpecial Weather StatementPSRRiverside70 min
Jul 30, 5:24 PM PDTFlash Flood Warning Considerable damage threatPSRRiverside4 hr
Jul 30, 5:29 PM PDTSevere Thunderstorm WarningPSRImperial46 min
Jul 30, 5:33 PM PDTFlash Flood Warning Considerable damage threatPSRImperial4 hr
Jul 30, 5:39 PM PDTAreal Flood AdvisoryPSRImperial3 hr
Jul 30, 5:52 PM PDTFlash Flood Warning Considerable damage threatPSRRiverside4 hr
Jul 30, 5:59 PM PDTDust Storm WarningPSRImperial45 min
Jul 30, 6:06 PM PDTFlash Flood Warning Considerable damage threatPSRImperial4 hr
Jul 30, 6:11 PM PDTSevere Thunderstorm WarningPSRRiverside79 min
Jul 30, 6:31 PM PDTSpecial Weather StatementPSRImperial74 min
Jul 30, 6:49 PM PDTFlash Flood Warning Considerable damage threatPSRImperial, Riverside4 hr
Jul 31, 2:32 PM PDTSpecial Weather StatementPSRRiverside28 min
Jul 31, 3:47 PM PDTSpecial Weather StatementPSRRiverside28 min

Nearby

Flash Flood Warnings in California, 2021Every 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.