Alert archive / California / Flash Flood Warnings in 2021

Flash Flood Warning 8, NWS San Diego, CA

July 30, 2021Riverside County, California

NWS San Diego, CA issued this flash flood warning at Jul 30, 2021, 3:48 PM PDT for Riverside County, California. It was in force for 3 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 30, 2021, 3:48 PM PDT (22:48 UTC)
Expired: Jul 30, 2021, 6:45 PM PDT
In force: 3 hr
Issued by: NWS San Diego, CA
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

County Riverside County, CA

The radar

The San Diego radar (KNKX), 90 km from the middle of the area, began a volume at 22:49 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.

What was reported inside it

Time	Report	Where	Remark
Jul 30, 4:00 PM PDT	HEAVY RAIN 2.56	5 N Anza, CA	THOMAS MOUNTAIN HADS GAUGE REPORT 2.56 INCHES OF RAINFALL. APPEARS TO BE IN ABOUT 60 TO 90 MINUTES DURATION. THIS IS LOCATED JUST SOUTH OF LAKE HEMET ALONG HIGHWAY 74.

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, 10.8 hours before the alert went out and 108 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: 2147 m above ground
0-6 km bulk shear: 10 kt
0-1 km storm-relative helicity: -15 m²/s²
0-3 km storm-relative helicity: 37 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

623 
WGUS56 KSGX 302248
FFWSGX
CAC065-310145-
/O.NEW.KSGX.FF.W.0008.210730T2248Z-210731T0145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service San Diego CA
348 PM PDT Fri Jul 30 2021

The National Weather Service in San Diego has issued a

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

* Until 645 PM PDT.

* At 348 PM PDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 2 and 4 inches of rain 
  have fallen. The expected rainfall rate is 1 to 3 inches in 2 
  hours. 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...
  Southeastern Palm Springs, Anza, Idyllwild-Pine Cove, Mt San 
  Jacinto State Park, Hwy 243 Between Banning And Idyllwild, Hwy 74 
  Between Mountain Center And Anza, Hwy 74 Between Anza And Palm 
  Desert, Mountain Center, Hwy 74 Between Hemet And Mountain Center, 
  Aguanga, Lake Hemet, Cahuilla Indian Reservation, Santa Rosa 
  Mountain and Sage.

This includes the following streams and drainages...
  Temecula Creek, Chihuahua Creek, Iron Spring Canyon, Cooper Canyon 
  and Coyote Creek.

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 3369 11688 3382 11675 3381 11665 3376 11654
      3343 11617 3343 11675

FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE
EXPECTED RAINFALL...1-3 INCHES IN 2 HOURS

$$

Brotherton

2 follow-up statements

068 
WGUS76 KSGX 310053
FFSSGX

Flash Flood Statement
National Weather Service San Diego CA
553 PM PDT Fri Jul 30 2021

CAC065-310145-
/O.CON.KSGX.FF.W.0008.000000T0000Z-210731T0145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Riverside CA-
553 PM PDT Fri Jul 30 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 645 PM PDT THIS 
EVENING FOR RIVERSIDE COUNTY...

At 553 PM PDT, Doppler radar indicated thunderstorms had ended 
across the warned area, however rain showers are continuing and 
could exacerbate any ongoing flooding problems, therefore the 
warning will remain in effect.

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...
  Southeastern Palm Springs, Anza, Idyllwild-Pine Cove, Mt San 
  Jacinto State Park, Hwy 243 Between Banning And Idyllwild, Hwy 74 
  Between Mountain Center And Anza, Hwy 74 Between Anza And Palm 
  Desert, Mountain Center, Hwy 74 Between Hemet And Mountain Center, 
  Aguanga, Lake Hemet, Cahuilla Indian Reservation, Santa Rosa 
  Mountain and Sage.

This includes the following streams and drainages...
  Temecula Creek, Chihuahua Creek, Iron Spring Canyon, Cooper Canyon 
  and Coyote Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Move away from recently burned areas. Life-threatening flooding of 
creeks, roads and normally dry arroyos is likely. The heavy rains 
will likely trigger rockslides, mudslides and debris flows in steep 
terrain, especially in and around these areas.

&&

LAT...LON 3369 11688 3382 11675 3381 11665 3376 11654
      3343 11617 3343 11675

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

$$

Brotherton

556 
WGUS76 KSGX 310136
FFSSGX

Flash Flood Statement
National Weather Service San Diego CA
636 PM PDT Fri Jul 30 2021

CAC065-310146-
/O.EXP.KSGX.FF.W.0008.000000T0000Z-210731T0145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Riverside CA-
636 PM PDT Fri Jul 30 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 645 PM PDT THIS EVENING 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 3369 11688 3382 11675 3381 11665 3376 11654
      3343 11617 3343 11675

$$

Brotherton

The office that day

Everything else NWS San Diego, CA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 30, 1:41 PM PDT	Areal Flood Advisory	SGX	San Bernardino	4 hr
Jul 30, 2:38 PM PDT	Flash Flood Warning	SGX	Riverside, San Diego	2 hr
Jul 30, 2:48 PM PDT	Areal Flood Advisory	SGX	Riverside	3 hr
Jul 30, 2:54 PM PDT	Areal Flood Advisory	SGX	San Bernardino	3 hr
Jul 30, 3:17 PM PDT	Severe Thunderstorm Warning	SGX	Riverside	58 min

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.