Alert archive / California / Flash Flood Warnings in 2021

Flash Flood Warning 2, NWS Los Angeles, CA

January 28, 2021San Luis Obispo County, California

NWS Los Angeles, CA issued this flash flood warning at Jan 28, 2021, 1:34 AM PST for San Luis Obispo County, California. It was in force for 56 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued
Jan 28, 2021, 1:34 AM PST (09:34 UTC)
Expired
Jan 28, 2021, 2:30 AM PST
In force
56 min
Issued by
NWS Los Angeles, CA
Area
Storm-based polygon
Flood severity
None

County San Luis Obispo County, CA

The radar

The Vandenberg AFB radar (KVBX), 57 km from the middle of the area, began a volume at 09:34 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

Vandenberg AFB, CA (KVBG), launched 00:00Z, 9.6 hours before the alert went out and 61 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, Vandenberg AFB, CA at 00:00Z on 2021-01-28Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 8 joules per kilogram.LCLLFCEL10008507005003002001001 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, Vandenberg AFB, CA at 00:00Z on 2021-01-28The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 628 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
8 J/kg
Mixed-layer CIN
-67 J/kg
Mixed-layer LCL
489 m above ground
0-6 km bulk shear
77 kt
0-1 km storm-relative helicity
628 m²/s²
0-3 km storm-relative helicity
730 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

050 
WGUS56 KLOX 280934
FFWLOX
CAC079-281030-
/O.NEW.KLOX.FF.W.0002.210128T0934Z-210128T1030Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Los Angeles/Oxnard CA
134 AM PST Thu Jan 28 2021

The National Weather Service in Los Angeles/Oxnard has issued a

* Flash Flood Warning for...
  Central San Luis Obispo County in southwestern California...

* Until 230 AM PST.

* At 134 AM PST, Doppler radar and automated rain gauges indicated 
  heavy rain falling across the warned area. Flash flooding is 
  ongoing or expected to begin shortly.

  HAZARD...Flash flooding caused by heavy rain.

  SOURCE...Radar and automated gauges.

  IMPACT...Flash flooding of small creeks and streams, urban
           areas, highways, streets and underpasses as well as
           other poor drainage and low-lying areas.

* Some locations that will experience flash flooding include...
  San Luis Obispo, Morro Bay, Avila Beach including the Avila Burn 
  Scar, Shell Beach, Baywood-Los Osos, Diablo Canyon, Highway 101 
  over Cuesta Grade and Santa Margarita.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3513 12086 3513 12087 3514 12088 3514 12089
      3515 12091 3515 12092 3515 12093 3517 12094
      3536 12088 3536 12086 3540 12062 3519 12052

FLASH FLOOD...RADAR AND GAUGE INDICATED

$$

Kaplan/Bruno
1 follow-up statement
408 
WGUS76 KLOX 281034
FFSLOX

Flash Flood Statement
National Weather Service Los Angeles/Oxnard CA
234 AM PST Thu Jan 28 2021

CAC079-281044-
/O.EXP.KLOX.FF.W.0002.000000T0000Z-210128T1030Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
San Luis Obispo CA-
234 AM PST Thu Jan 28 2021

...FLASH FLOOD WARNING HAS EXPIRED FOR CENTRAL SAN LUIS OBISPO 
COUNTY...

Moderate rainfall will continue across the area this morning. Some 
heavier rain off the coast will likely move onshore, and additional 
flash flood warnings may be needed.

A Flash Flood Watch remains in effect until 1000 PM PST Thursday for 
a portion of southwest California.

LAT...LON 3513 12086 3513 12087 3514 12088 3514 12089
      3515 12091 3515 12092 3515 12093 3517 12094
      3536 12088 3536 12086 3540 12062 3519 12052

$$

DB

The office that day

Everything else NWS Los Angeles, CA issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jan 27, 11:48 PM PSTAreal Flood AdvisoryLOXSan Luis Obispo10 hr
Jan 28, 12:02 AM PSTFlash Flood WarningLOXSan Luis Obispo4 hr
Jan 28, 3:01 AM PSTFlash Flood WarningLOXSan Luis Obispo104 min
Jan 28, 5:49 AM PSTAreal Flood AdvisoryLOXSanta Barbara8 hr
Jan 28, 1:03 PM PSTAreal Flood AdvisoryLOXSanta Barbara6 hr
Jan 28, 2:16 PM PSTSmall Craft AdvisoryLOX7 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.