Alert archive / California / Flash Flood Warnings in 2021

Flash Flood Warning 107, NWS Las Vegas, NV

August 10, 2021San Bernardino County, California

NWS Las Vegas, NV issued this flash flood warning at Aug 10, 2021, 11:22 PM PDT for 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
Aug 10, 2021, 11:22 PM PDT (06:22 UTC)
Expired
Aug 11, 2021, 2:30 AM PDT
In force
3 hr
Issued by
NWS Las Vegas, NV
Area
Storm-based polygon
Damage threat
Considerable
Flood severity
None

County San Bernardino County, CA

The radar

The Edwards AFB radar (KEYX), 89 km from the middle of the area, began a volume at 06:21 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

Las Vegas, NV (KVEF), launched 00:00Z, 6.4 hours before the alert went out and 198 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, Las Vegas, NV at 00:00Z on 2021-08-11Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 656 joules per kilogram.LCLEL10008507005003002001001 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, Las Vegas, NV at 00:00Z on 2021-08-11The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 41 square meters per square second.1939Sfc1 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
656 J/kg
Mixed-layer CIN
-12 J/kg
Mixed-layer LCL
3298 m above ground
0-6 km bulk shear
11 kt
0-1 km storm-relative helicity
41 m²/s²
0-3 km storm-relative helicity
92 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

521 
WGUS55 KVEF 110622
FFWVEF
CAC071-110930-
/O.NEW.KVEF.FF.W.0107.210811T0622Z-210811T0930Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Las Vegas NV
1122 PM PDT Tue Aug 10 2021

The National Weather Service in Las Vegas has issued a

* Flash Flood Warning for...
  Western San Bernardino County in southern California...

* Until 230 AM PDT.

* At 1122 PM PDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 2 and 3 inches of rain 
  has fallen thus far. 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 low-water
           crossings, normally dry washes and roads.

* Some locations that will experience flash flooding include...
  Newberry Springs.

This includes the following highways...
	Interstate 40 in California between mile markers 17 and 30.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be aware of your surroundings and do not drive on flooded roads.

Please report observed flooding to local emergency services or law 
enforcement and request they pass this information to the National 
Weather Service when you can do so safely.

&&

LAT...LON 3476 11678 3496 11665 3496 11645 3474 11652

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

$$

TL
1 follow-up statement
613 
WGUS75 KVEF 110927
FFSVEF

Flash Flood Statement
National Weather Service Las Vegas NV
227 AM PDT Wed Aug 11 2021

CAC071-110937-
/O.EXP.KVEF.FF.W.0107.000000T0000Z-210811T0930Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
San Bernardino CA-
227 AM PDT Wed Aug 11 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 230 AM PDT EARLY THIS MORNING 
FOR WESTERN SAN BERNARDINO COUNTY...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat. Please continue to heed remaining road closures.

LAT...LON 3476 11678 3496 11665 3496 11645 3474 11652

$$

TL

The office that day

Everything else NWS Las Vegas, NV issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 10, 5:13 PM PDTSevere Thunderstorm WarningVEFSan Bernardino92 min
Aug 10, 5:49 PM PDTDust Storm WarningVEFSan Bernardino56 min
Aug 10, 6:43 PM PDTSevere Thunderstorm WarningVEFSan Bernardino47 min
Aug 10, 6:55 PM PDTFlash Flood Warning Considerable damage threatVEFSan Bernardino3 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.