Alert archive / California / Flash Flood Warnings in 2023

Flash Flood Warning 12, NWS Phoenix, AZ

August 18, 2023Riverside County, San Bernardino County, California

NWS Phoenix, AZ issued this flash flood warning at Aug 18, 2023, 4:47 PM PDT for Riverside County, San Bernardino 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 counties it named.

The facts

Issued: Aug 18, 2023, 4:47 PM PDT (23:47 UTC)
Expired: Aug 18, 2023, 8:15 PM PDT
In force: 3 hr
Issued by: NWS Phoenix, AZ
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

Counties Riverside County, CA, San Bernardino County, CA

The radar

The Santa Ana Mts radar (KSOX), 152 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 195 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: 2135 m above ground
0-6 km bulk shear: 29 kt
0-1 km storm-relative helicity: 4 m²/s²
0-3 km storm-relative helicity: 10 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this flash flood warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Phoenix, AZ wrote its last area forecast discussion before this flash flood warning went out at Aug 18, 3:58 PM PDT, 49 minutes earlier.

Area forecast discussion, Aug 18, 3:58 PM PDT, 49 minutes before

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In the hours before

Special weather statement, Aug 18, 4:09 PM PDT, 38 minutes before

Special Weather Statement
National Weather Service Phoenix AZ
409 PM PDT Fri Aug 18 2023

CAZ561-568-570-182345-
Chuckwalla Valley CA-Chiriaco Summit CA-Joshua Tree NP East CA-
409 PM PDT Fri Aug 18 2023

...A strong thunderstorm will impact portions of San Bernardino and
Riverside Counties through 445 PM PDT...

At 409 PM PDT, Doppler radar was tracking a strong thunderstorm 7
miles east of Eagle Mtn, or 10 miles north of Desert Center, moving
north at 20 mph.

HAZARD...Wind gusts up to 50 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Desert Center and Eagle Mtn.

This includes the following highways...
CA Interstate 10 between mile markers 102 and 106.
CA Route 177 between mile markers 1 and 23.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3407 11532 3408 11526 3377 11516 3369 11546
      3404 11562 3404 11560 3409 11560 3408 11554
      3411 11552
TIME...MOT...LOC 2309Z 164DEG 16KT 3386 11535

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 MPH

GL

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 17, 5:06 PM PDT	Severe Thunderstorm Warning	PSR	Maricopa, Pinal	39 min
Aug 17, 5:18 PM PDT	Severe Thunderstorm Warning	PSR	Maricopa	12 min
Aug 17, 5:43 PM PDT	Severe Thunderstorm Warning	PSR	Maricopa, Pinal	32 min
Aug 17, 5:51 PM PDT	Areal Flood Advisory	PSR	Maricopa, Pinal	25 min
Aug 17, 6:11 PM PDT	Severe Thunderstorm Warning	PSR	Maricopa, Pinal	34 min
Aug 17, 6:16 PM PDT	Flash Flood Warning	PSR	Maricopa, Pinal	119 min
Aug 17, 6:57 PM PDT	Special Weather Statement	PSR		33 min
Aug 17, 7:03 PM PDT	Dust Storm Advisory	PSR	Maricopa, Pinal	42 min
Aug 17, 7:34 PM PDT	Special Weather Statement	PSR	La Paz	41 min
Aug 17, 9:15 PM PDT	Flash Flood Warning Considerable damage threat	PSR	La Paz, Yuma	3 hr
Aug 18, 1:18 PM PDT	Wind Advisory	PSR	La Paz, Maricopa, Pinal, Yuma	60 hr
Aug 18, 4:09 PM PDT	Special Weather Statement	PSR		36 min
Aug 18, 4:05 PM PDT	Areal Flood Advisory	PSR	Riverside, San Bernardino	42 min

Nearby

Flash Flood Warnings in California, 2023 Every flash flood warning in 2023

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.