Alert archive / California / Flash Flood Watches in 2021

Flash Flood Watch 8, NWS San Diego, CA

September 24, 2021Riverside County, San Diego County, California

NWS San Diego, CA issued this flash flood watch at Sep 24, 2021, 8:56 AM PDT for Riverside County, San Diego County, California. It took effect at Sep 24, 2021, 10:00 AM PDT. It was in force for 9 hr.

The area

The counties it named.

The facts

Issued
Sep 24, 2021, 8:56 AM PDT (15:56 UTC)
In effect from
Sep 24, 2021, 10:00 AM PDT
Expired
Sep 24, 2021, 7:00 PM PDT
In force
9 hr
Issued by
NWS San Diego, CA
Flood severity
None

Counties Riverside County, CA, San Diego County, CA

The radar

The San Diego radar (KNKX), 80 km from the middle of the area, began a volume at 15:57 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, 3.9 hours before the alert went out and 100 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 2021-09-24Temperature 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 12:00Z on 2021-09-24The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -36 square meters per square second.1939587897Sfc1 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
1990 m above ground
0-6 km bulk shear
4 kt
0-1 km storm-relative helicity
-36 m²/s²
0-3 km storm-relative helicity
15 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

274 
WGUS66 KSGX 241556
FFASGX

URGENT - IMMEDIATE BROADCAST REQUESTED
Flood Watch
National Weather Service San Diego CA
856 AM PDT Fri Sep 24 2021

CAZ056-058-061-062-250200-
/O.NEW.KSGX.FF.A.0008.210924T1700Z-210925T0200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Riverside County Mountains-San Diego County Mountains-Coachella
Valley-San Diego County Deserts-
Including the cities of Palm Desert, Indio, La Quinta, 
Idyllwild-Pine Cove, Julian, Palm Desert Country, Pine Valley, Palm 
Springs, Coachella, Borrego Springs, and Cathedral City
856 AM PDT Fri Sep 24 2021

...FLASH FLOOD WATCH IN EFFECT UNTIL 7 PM PDT THIS EVENING...

The National Weather Service in San Diego has issued a

* Flash Flood Watch for a portion of southwest California, including 
  the following areas: Coachella Valley, Riverside County Mountains, 
  San Diego County Deserts and San Diego County Mountains.

* Until 7 PM PDT this evening.

* Areas of showers and thunderstorms are expected across the region. 
  Some of these will produce heavy rain that may lead to localized 
  flash flooding.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

You should monitor later forecasts and be prepared to take action 
should Flash Flood Warnings be issued. Turn around, don't drown!

&&

$$

APR
1 follow-up statement
648 
WGUS66 KSGX 250153
FFASGX

Flood Watch
National Weather Service San Diego CA
653 PM PDT Fri Sep 24 2021

CAZ056-058-061-062-250300-
/O.EXP.KSGX.FF.A.0008.000000T0000Z-210925T0200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Riverside County Mountains-San Diego County Mountains-Coachella
Valley-San Diego County Deserts-
Including the cities of Palm Desert, Indio, La Quinta, 
Idyllwild-Pine Cove, Julian, Palm Desert Country, Pine Valley, Palm 
Springs, Coachella, Borrego Springs, and Cathedral City
653 PM PDT Fri Sep 24 2021

...FLASH FLOOD WATCH WILL EXPIRE AT 7 PM PDT THIS EVENING...

The Flash Flood Watch for the Coachella Valley, Riverside County 
Mountains, San Diego County Deserts and San Diego County Mountains 
will expire at 7 PM this evening.

Flooding is no longer expected to pose a threat. Please continue to 
heed remaining road closures.

$$

Moede

The office that day

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

IssuedProductOfficeCountiesLasted
Sep 24, 11:08 AM PDTBeach Hazards StatementSGXOrange, San Diego8 hr
Sep 24, 12:13 PM PDTSevere Thunderstorm WarningSGXSan Diego31 min
Sep 24, 12:21 PM PDTFlash Flood Warning Considerable damage threatSGXSan Diego56 min
Sep 24, 1:24 PM PDTSevere Thunderstorm WarningSGXSan Diego51 min
Sep 24, 1:28 PM PDTFlash Flood Warning Considerable damage threatSGXSan Diego2 hr
Sep 24, 2:09 PM PDTFlash Flood Warning Considerable damage threatSGXSan Diego3 hr
Sep 24, 2:41 PM PDTSevere Thunderstorm WarningSGXSan Diego64 min
Sep 24, 2:59 PM PDTSpecial Weather StatementSGXSan Diego61 min
Sep 24, 3:14 PM PDTSpecial Marine WarningSGX91 min
Sep 24, 3:20 PM PDTSevere Thunderstorm WarningSGXSan Diego55 min
Sep 24, 3:47 PM PDTSpecial Weather StatementSGXOrange58 min
Sep 24, 3:56 PM PDTSpecial Marine WarningSGX94 min
Sep 24, 4:40 PM PDTSpecial Marine WarningSGX65 min

Nearby

Flash Flood Watches in California, 2021Every flash flood watch 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.