Alert archive / Arizona / Flash Flood Warnings in 2021

Flash Flood Warning 112, NWS Las Vegas, NV

August 12, 2021Mohave County, Arizona; Clark County, Nevada

NWS Las Vegas, NV issued this flash flood warning at Aug 12, 2021, 8:42 PM MST for Mohave County, Arizona; Clark County, Nevada. It was in force for 3 hr. 1 report came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Aug 12, 2021, 8:42 PM MST (03:42 UTC)
Expired: Aug 12, 2021, 11:45 PM MST
In force: 3 hr
Issued by: NWS Las Vegas, NV
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

Counties Mohave County, AZ, Clark County, NV

The radar

The Las Vegas radar (KESX), 48 km from the middle of the area, began a volume at 03:47 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.

What was reported inside it

Time	Report	Where	Remark
Aug 12, 9:30 PM MST	FLASH FLOOD	4 Ne Las Vegas Bay, NV	DELAYED REPORT...NPS REPORTS FLOODING AND DEBRIS OVER THE ROADWAY ON MILE POST 8 ON NORTHSHORE ROAD FROM THUNDERSTORMS THURSDAY EVENING. TIM ESTIMATED BY RADAR.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Las Vegas, NV (KVEF), launched 00:00Z, 3.7 hours before the alert went out and 75 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: 1235 J/kg
Mixed-layer CIN: -41 J/kg
Mixed-layer LCL: 2944 m above ground
0-6 km bulk shear: 15 kt
0-1 km storm-relative helicity: 2 m²/s²
0-3 km storm-relative helicity: 96 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

347 
WGUS55 KVEF 130342
FFWVEF
AZC015-NVC003-130645-
/O.NEW.KVEF.FF.W.0112.210813T0342Z-210813T0645Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Las Vegas NV
842 PM PDT Thu Aug 12 2021

The National Weather Service in Las Vegas has issued a

* Flash Flood Warning for...
  West Central Mohave County in northwestern Arizona...
  Southeastern Clark County in southern Nevada...

* Until 1145 PM MST /1145 PM PDT/.

* At 842 PM MST /842 PM PDT/, Doppler radar indicated thunderstorms 
  producing heavy rain near Lake Las Vegas. Flash flooding is 
  ongoing or expected to begin shortly and will impact lake Las 
  Vegas...Northshore Road...and Lakeshore road. Additional heavy 
  rain may develop in the next hour down to Boulder Beach and the 
  Hoover Dam.

  HAZARD...Life-threatening flash flooding. Thunderstorms
           producing flash flooding.

  SOURCE...Radar.

  IMPACT...Life-threatening flash flooding of low-water
           crossings, creeks, normally dry washes and roads.

* Some locations that will experience flash flooding include...
  Boulder City, Las Vegas Bay, Callville Bay, Callville Bay 
  Campground, Boulder Beach, Boulder Beach Campground, Las Vegas Bay 
  Campground and Hoover Dam.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3603 11490 3627 11489 3629 11486 3631 11467
      3605 11458 3604 11458 3597 11472

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

$$

CO

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 12, 5:24 PM MST	Flash Flood Warning Considerable damage threat	VEF	Mohave	111 min
Aug 12, 5:43 PM MST	Flash Flood Warning Considerable damage threat	VEF	Mohave	3 hr
Aug 12, 8:17 PM MST	Severe Thunderstorm Warning	VEF	Mohave	58 min
Aug 12, 8:54 PM MST	Flash Flood Warning Considerable damage threat	VEF	Mohave	3 hr
Aug 12, 9:10 PM MST	Severe Thunderstorm Warning	VEF	Mohave	50 min
Aug 12, 10:56 PM MST	Flash Flood Warning Considerable damage threat	VEF	Mohave	3 hr
Aug 12, 7:06 PM MST	Severe Thunderstorm Warning	VEF	Clark	39 min
Aug 12, 7:40 PM MST	Severe Thunderstorm Warning	VEF	Clark	50 min
Aug 12, 7:46 PM MST	Flash Flood Warning Considerable damage threat	VEF	Clark	3 hr
Aug 13, 2:37 AM MST	Excessive Heat Watch	VEF	Clark, Nye	12 hr
Aug 13, 2:18 PM MST	Excessive Heat Warning	VEF	Clark, Nye	3 days
Aug 13, 2:23 PM MST	Severe Thunderstorm Warning	VEF	Clark	52 min

Nearby

Flash Flood Warnings in Arizona, 2021 Flash Flood Warnings in Nevada, 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.