Alert archive / California / Flash Flood Warnings in 2021

Flash Flood Warning 237, NWS Phoenix, AZ

August 31, 2021Imperial County, Riverside County, California

NWS Phoenix, AZ issued this flash flood warning at Aug 31, 2021, 5:58 PM PDT for Imperial County, Riverside County, California. It was in force for 8 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: Aug 31, 2021, 5:58 PM PDT (00:58 UTC)
Expired: Sep 1, 2021, 2:00 AM PDT
In force: 8 hr
Issued by: NWS Phoenix, AZ
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

Counties Imperial County, CA, Riverside County, CA

The radar

The San Diego radar (KNKX), 149 km from the middle of the area, began a volume at 00:59 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, 1.0 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-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: 853 m above ground
0-6 km bulk shear: 15 kt
0-1 km storm-relative helicity: -77 m²/s²
0-3 km storm-relative helicity: -65 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

229 
WGUS55 KPSR 010058
FFWPSR
CAC025-065-010900-
/O.NEW.KPSR.FF.W.0237.210901T0058Z-210901T0900Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

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

The National Weather Service in Phoenix has issued a

* Flash Flood Warning for...
  Northwestern Imperial County in southeastern California...
  Riverside County in southern California...

* Until 200 AM PDT Wednesday.

* At 558 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 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...
  Chiriaco Summit, Desert Center, North Shore and Cottonwood Visitor 
  Center.

This includes the following highways...
	CA Route 111 between mile markers 64 and 65.
	CA Interstate 10 between mile markers 100 and 109.
	CA Route 177 between mile markers 1 and 7.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3377 11604 3375 11583 3384 11566 3378 11551
      3378 11546 3381 11534 3375 11528 3366 11530
      3364 11538 3360 11571 3339 11582 3350 11597
      3351 11597 3351 11595 3374 11595 3374 11600

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

$$

Hirsch

2 follow-up statements

187 
WGUS75 KPSR 010328
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
828 PM PDT Tue Aug 31 2021

CAC025-065-010900-
/O.CON.KPSR.FF.W.0237.000000T0000Z-210901T0900Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Imperial CA-Riverside CA-
828 PM PDT Tue Aug 31 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 2 AM PDT WEDNESDAY 
FOR NORTHWESTERN IMPERIAL AND RIVERSIDE COUNTIES...

At 828 PM PDT, Doppler radar indicated thunderstorms have produced 
heavy rain across the warned area. Up to 2 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...
  Chiriaco Summit, Desert Center, North Shore and Cottonwood Visitor 
  Center.

This includes the following highways...
	CA Route 111 between mile markers 64 and 65.
	CA Interstate 10 between mile markers 100 and 109.
	CA Route 177 between mile markers 1 and 7.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3377 11604 3375 11583 3384 11566 3378 11551
      3378 11546 3381 11534 3375 11528 3366 11530
      3364 11538 3360 11571 3339 11582 3350 11597
      3351 11597 3351 11595 3374 11595 3374 11600

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

$$

CK

244 
WGUS75 KPSR 010901
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
201 AM PDT Wed Sep 1 2021

CAC025-065-010911-
/O.EXP.KPSR.FF.W.0237.000000T0000Z-210901T0900Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Imperial CA-Riverside CA-
201 AM PDT Wed Sep 1 2021

...FLASH FLOOD WARNING HAS EXPIRED FOR NORTHWESTERN IMPERIAL AND 
RIVERSIDE COUNTIES...

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

LAT...LON 3377 11604 3375 11583 3384 11566 3378 11551
      3378 11546 3381 11534 3375 11528 3366 11530
      3364 11538 3360 11571 3339 11582 3350 11597
      3351 11597 3351 11595 3374 11595 3374 11600

$$

CK

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 31, 5:12 PM PDT	Flash Flood Warning Considerable damage threat	PSR	Imperial, Riverside	6 hr
Aug 31, 7:41 PM PDT	Flash Flood Warning Considerable damage threat	PSR	Imperial	8 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.