Alert archive / California / Flash Flood Warnings in 2021

Flash Flood Warning 3, NWS Los Angeles, CA

January 28, 2021San Luis Obispo County, California

NWS Los Angeles, CA issued this flash flood warning at Jan 28, 2021, 3:01 AM PST for San Luis Obispo County, California. It was in force for 104 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, 3:01 AM PST (11:01 UTC)
Expired: Jan 28, 2021, 4:45 AM PST
In force: 104 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), 45 km from the middle of the area, began a volume at 11:03 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, 11.0 hours before the alert went out and 52 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: 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.

441 
WGUS56 KLOX 281101
FFWLOX
CAC079-281245-
/O.NEW.KLOX.FF.W.0003.210128T1101Z-210128T1245Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

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

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

* Flash Flood Warning for...
  The Avila Burn Scar in...
  Southwestern San Luis Obispo County in southwestern California...

* Until 445 AM PST.

* At 301 AM PST, Doppler radar indicated heavy rain approaching the 
  Avila Burn Scar. Between 2 and 3 inches of rain have fallen. The 
  expected rainfall rate is 0.75 to 1 inch in 1 hour. Additional 
  rainfall amounts of 2 to 5 inches are possible in the warned area. 
  Flash flooding is ongoing or expected to begin shortly.

Excessive rainfall over the Avila burn scar will result in debris 
flows causing local damage. The debris flows can consist of rock, 
mud, vegetation and other loose materials.

  HAZARD...Flash flooding caused by heavy rain in and around the
           Avila Burn Scar.

  SOURCE...Radar.

  IMPACT...Flooding of directly below theAvila Burn Scar.

* Some locations that will experience flash flooding include...
  Areas in and around the Avila Burn Scar. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...


A Flash Flood Warning for a recent burn area means that flooding and 
debris flows are imminent or occurring. Residents living in or 
immediately downstream should take immediate precautions to protect 
life and property. Quickly move away from the burn area only if it 
is safe to do so, otherwise shelter in place and move to a second 
story or the highest location in your home to stay out of the path 
of fast-moving water and debris flows.

&&

LAT...LON 3518 12070 3517 12067 3515 12067 3517 12071

FLASH FLOOD...RADAR INDICATED
EXPECTED RAINFALL...0.75-1 INCH IN 1 HOUR

$$

NWS Los Angeles/Oxnard

1 follow-up statement

829 
WGUS76 KLOX 281244
FFSLOX

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

CAC079-281254-
/O.EXP.KLOX.FF.W.0003.000000T0000Z-210128T1245Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
San Luis Obispo CA-
444 AM PST Thu Jan 28 2021

...FLASH FLOOD WARNING FOR THE AVILA BURN SCAR WILL EXPIRE AT 445 AM 
PST EARLY THIS MORNING FOR SOUTHWESTERN SAN LUIS OBISPO COUNTY...

The heavy rain has decreased in intensity across the Avila Burn 
area.. Flooding is no longer expected to pose an immediate threat. 
However, please continue to heed remaining road closures.

A Flash Flood Watch remains in effect until 1000 PM PST this evening 
for the San Luis Obispo County Central Coast and adjacent foothills.


LAT...LON 3518 12070 3517 12067 3515 12067 3517 12071

$$

DB

The office that day

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

Issued	Product	Office	Counties	Lasted
Jan 27, 11:48 PM PST	Areal Flood Advisory	LOX	San Luis Obispo	10 hr
Jan 28, 12:02 AM PST	Flash Flood Warning	LOX	San Luis Obispo	4 hr
Jan 28, 1:34 AM PST	Flash Flood Warning	LOX	San Luis Obispo	56 min
Jan 28, 5:49 AM PST	Areal Flood Advisory	LOX	Santa Barbara	8 hr
Jan 28, 1:03 PM PST	Areal Flood Advisory	LOX	Santa Barbara	6 hr
Jan 28, 2:16 PM PST	Small Craft Advisory	LOX		7 hr

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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.