Alert archive / California / Flash Flood Warnings in 2021

Flash Flood Warning 24, NWS San Diego, CA

December 24, 2021Riverside County, San Bernardino County, California

NWS San Diego, CA issued this flash flood warning at Dec 24, 2021, 1:17 AM PST 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 outline as issued.

The facts

Issued
Dec 24, 2021, 1:17 AM PST (09:17 UTC)
Expired
Dec 24, 2021, 4:15 AM PST
In force
3 hr
Issued by
NWS San Diego, CA
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), 73 km from the middle of the area, began a volume at 09:20 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, 9.3 hours before the alert went out and 142 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 00:00Z on 2021-12-24Temperature 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 00:00Z on 2021-12-24The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 157 square meters per square second.1939587897117Sfc1 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
1578 m above ground
0-6 km bulk shear
86 kt
0-1 km storm-relative helicity
157 m²/s²
0-3 km storm-relative helicity
142 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

152 
WGUS56 KSGX 240917
FFWSGX
CAC065-071-241215-
/O.NEW.KSGX.FF.W.0024.211224T0917Z-211224T1215Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service San Diego CA
117 AM PST Fri Dec 24 2021

The National Weather Service in San Diego has issued a

* Flash Flood Warning for...
  The Apple and El Dorado burn scar in...
  Riverside County in southern California...
  San Bernardino County in southern California...

* Until 415 AM PST.

* At 117 AM PST, Doppler radar and automated rain gauges indicated 
  heavy rain falling over the Apple and El Dorado Burn Scar. The 
  expected rainfall rate is 0.5 to 0.75 inches in 1 hour. Flash 
  flooding is ongoing or expected to begin shortly. Raywood Flats 
  has reported 0.60" of rain in the last hour.

Excessive rainfall over the burn scar will result in debris flow 
moving through the Birch Creek, Potato Canyon, Little San Gorgonio 
Creek, Forsee Creek, Glen Martin Creek, Oak Glen Creek, Wilson 
Creek, Mountain Home Creek, San Gorgonio River, Portrero Creek, Mias 
Canyon, Corral Canyon, Millard Canyon, and the south fork of the 
Whitewater River. The debris flow can consist of rock, mud, 
vegetation and other loose materials.

  HAZARD...Life threatening flash flooding. Heavy rain producing
           flash flooding in and around the Apple and El Dorado
           Burn Scar.

  SOURCE...Radar and automated gauges.

  IMPACT...Life threatening flash flooding of areas in and around
           the Apple and El Dorado Burn Scar.

* Some locations that will experience flash flooding include...
  Yucaipa, Forest Falls, southeastern Mount San Gorgonio, Beaumont, 
  Banning, Hwy 38 Between Yucaipa And Onyx Summit, Mountain Home 
  Village, Angelus Oaks, Cherry Valley and Morongo Indian 
  Reservation.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This is a life threatening situation. Heavy rainfall may cause 
extensive and severe flash flooding of creeks, streams, and ditches 
in the El Dorado and Apple Burn Scars. Severe debris flows can also 
be anticipated across roads. Roads and driveways may be washed away 
in places. If you encounter flood waters, climb to safety.

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

&&

LAT...LON 3403 11702 3410 11703 3411 11698 3414 11698
      3412 11693 3410 11695 3407 11689 3409 11685
      3409 11678 3409 11676 3407 11677 3404 11679
      3403 11677 3399 11678 3396 11679 3394 11694
      3396 11697 3400 11697

FLASH FLOOD...RADAR AND GAUGE INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE
EXPECTED RAINFALL RATE...0.5-0.75 INCHES IN 1 HOUR

$$

Connolly
1 follow-up statement
248 
WGUS76 KSGX 241212
FFSSGX

Flash Flood Statement
National Weather Service San Diego CA
412 AM PST Fri Dec 24 2021

CAC065-071-241222-
/O.EXP.KSGX.FF.W.0024.000000T0000Z-211224T1215Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Riverside CA-San Bernardino CA-
412 AM PST Fri Dec 24 2021

...FLASH FLOOD WARNING FOR THE APPLE AND EL DORADO BURN SCAR WILL 
EXPIRE AT 415 AM PST EARLY THIS MORNING FOR RIVERSIDE AND SAN 
BERNARDINO COUNTIES...

The heavy rain has ended. Light to moderate rain will continue over 
the burn scar through this morning. Flooding is no longer expected 
to pose a threat. Please continue to heed remaining road closures.

A Flood Watch remains in effect until 1200 PM PST Friday for a 
portion of Southern California.

LAT...LON 3403 11702 3410 11703 3411 11698 3414 11698
      3412 11693 3410 11695 3407 11689 3409 11685
      3409 11678 3409 11676 3407 11677 3404 11679
      3403 11677 3399 11678 3396 11679 3394 11694
      3396 11697 3400 11697

$$

Connolly

The office that day

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

IssuedProductOfficeCountiesLasted
Dec 23, 5:29 PM PSTAreal Flood AdvisorySGXRiverside, San Bernardino3 hr
Dec 23, 8:01 PM PSTAreal Flood AdvisorySGXOrange7 hr
Dec 23, 8:20 PM PSTAreal Flood AdvisorySGXRiverside, San Bernardino7 hr
Dec 23, 9:31 PM PSTAreal Flood AdvisorySGXSan Diego3 hr
Dec 23, 10:03 PM PSTWinter Storm WarningSGXRiverside, San Bernardino14 hr
Dec 24, 2:26 AM PSTAreal Flood AdvisorySGXSan Diego3 hr
Dec 24, 6:14 AM PSTBeach Hazards StatementSGXOrange, San Diego2 hr
Dec 24, 7:07 AM PSTAreal Flood AdvisorySGXOrange, Riverside, San Bernardino, San Diego2 hr
Dec 24, 7:31 AM PSTAreal Flood AdvisorySGXSan Diego90 min
Dec 24, 12:00 PM PSTWinter Storm WatchSGXRiverside, San Bernardino9 hr

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.