Alert archive / Arizona / Flash Flood Warnings in 2021

Flash Flood Warning 51, NWS Phoenix, AZ

July 21, 2021Maricopa County, Arizona

NWS Phoenix, AZ issued this flash flood warning at Jul 21, 2021, 4:26 PM MST for Maricopa County, Arizona. It was in force for 4 hr. 3 reports 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: Jul 21, 2021, 4:26 PM MST (23:26 UTC)
Expired: Jul 21, 2021, 8:00 PM MST
In force: 4 hr
Issued by: NWS Phoenix, AZ
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

County Maricopa County, AZ

The radar

The Phoenix radar (KIWA), 124 km from the middle of the area, began a volume at 23:28 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
Jul 21, 4:37 PM MST	FLASH FLOOD	Wickenburg, AZ	DELAYED REPORT. POWDER HOUSE WASH FLOODED THE INTERSECTION OF JACK BURDEN RD. AND CONSTELLATION RD REQUIRING SAND AND DEBRIS REMOVAL THE NEXT DAY BY PUBLIC WORKS. TIME ESTIMATED BASED ON UPSTREAM GAUGE.
Jul 21, 4:47 PM MST	HEAVY RAIN 2.09	2 Ene Wickenburg, AZ	FCDMC CONSTELLATION ROAD RAIN GAUGE REPORTS 2.09 INCHES OF RAIN FROM 3:57 PM MST TO 4:51 PM MST .
Jul 21, 6:00 PM MST	FLASH FLOOD	3 Se Wickenburg, AZ	DELAYED REPORT THE HASSAYAMPA RIVER PRESERVE REPORTED CLOSURE OF SEVERAL TRAILS DUE TO FLOOD WATER/DEBRIS WITH A SUDDEN RISE IN THE HASSAYAMPA RIVER. TRAILS WILL BE CLOSED THROUGH THE WEEKEND.

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

The nearest sounding before it

Phoenix, AZ (KPSR), launched 12:00Z, 11.4 hours before the alert went out and 93 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: 5 J/kg
Mixed-layer CIN: -244 J/kg
Mixed-layer LCL: 2438 m above ground
0-6 km bulk shear: 2 kt
0-1 km storm-relative helicity: -11 m²/s²
0-3 km storm-relative helicity: 11 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

344 
WGUS55 KPSR 212326
FFWPSR
AZC013-220300-
/O.NEW.KPSR.FF.W.0051.210721T2326Z-210722T0300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Phoenix AZ
426 PM MST Wed Jul 21 2021

The National Weather Service in Phoenix has issued a

* Flash Flood Warning for...
  Maricopa County in south central Arizona...

* Until 800 PM MST.

* At 426 PM MST, Doppler radar and automated rain gauges indicated 
  thunderstorms producing heavy rain across the warned area. Between 
  0.5 and 1.5 inches of rain have fallen. Flash flooding is ongoing 
  or expected to begin shortly.

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

  SOURCE...Radar and automated gauges.

  IMPACT...Life threatening flash flooding of creeks and streams,
           urban areas, highways, streets and underpasses.

* Some locations that will experience flash flooding include...
  Wickenburg.

Powerhouse Wash on the east side of Wickenburg.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3397 11264 3389 11267 3388 11287 3400 11284
      3400 11279 3400 11275 3400 11274

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

$$

MS

2 follow-up statements

151 
WGUS75 KPSR 220003
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
503 PM MST Wed Jul 21 2021

AZC013-220300-
/O.CON.KPSR.FF.W.0051.000000T0000Z-210722T0300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
503 PM MST Wed Jul 21 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 8 PM MST THIS EVENING 
FOR MARICOPA COUNTY...

At 503 PM MST, Doppler radar and automated rain gauges indicated 
thunderstorms producing heavy rain across the warned area. Between 1 
and 2 inches of rain have fallen. Additional rainfall amounts up to 
0.5 inches are possible in the warned area. Flash flooding is 
ongoing with rapid rises reported in area washes including Powder 
House Wash.

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

SOURCE...Radar and automated gauges.

IMPACT...Life threatening flash flooding of creeks and streams,
         urban areas, highways, streets and underpasses.

Some locations that will experience flash flooding include...
  Wickenburg.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3397 11264 3389 11267 3388 11287 3400 11284
      3400 11279 3400 11275 3400 11274

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

$$

MS

704 
WGUS75 KPSR 220255
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
755 PM MST Wed Jul 21 2021

AZC013-220305-
/O.EXP.KPSR.FF.W.0051.000000T0000Z-210722T0300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
755 PM MST Wed Jul 21 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 8 PM MST THIS EVENING FOR THE 
WICKENBURG AREA IN MARICOPA COUNTY...

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

LAT...LON 3397 11264 3389 11267 3388 11287 3400 11284
      3400 11279 3400 11275 3400 11274

$$

Iniguez

The office that day

Everything else NWS Phoenix, AZ issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 20, 5:15 PM MST	Special Weather Statement	PSR	La Paz	45 min
Jul 20, 5:21 PM MST	Special Weather Statement	PSR	Gila	39 min
Jul 20, 5:32 PM MST	Areal Flood Advisory	PSR	Maricopa	3 hr
Jul 20, 6:22 PM MST	Special Weather Statement	PSR		38 min
Jul 20, 7:22 PM MST	Special Weather Statement	PSR	Pinal	53 min
Jul 20, 8:19 PM MST	Special Weather Statement	PSR	Pinal	41 min
Jul 20, 8:56 PM MST	Special Weather Statement	PSR	Pinal	49 min
Jul 20, 11:51 PM MST	Special Weather Statement	PSR		39 min
Jul 21, 2:21 AM MST	Flash Flood Watch	PSR	Gila, Maricopa, Pinal	5 days
Jul 21, 8:12 AM MST	Blowing Dust Advisory	PSR	La Paz, Maricopa, Yuma	12 hr
Jul 21, 2:45 PM MST	Special Weather Statement	PSR		45 min
Jul 21, 2:46 PM MST	Dust Storm Warning	PSR	Pinal	40 min
Jul 21, 3:07 PM MST	Special Weather Statement	PSR		38 min
Jul 21, 3:34 PM MST	Special Weather Statement	PSR	Maricopa	41 min
Jul 21, 3:37 PM MST	Special Weather Statement	PSR	La Paz	38 min
Jul 21, 3:42 PM MST	Special Weather Statement	PSR	Yuma	48 min
Jul 21, 3:45 PM MST	Special Weather Statement	PSR	Maricopa	45 min
Jul 21, 3:46 PM MST	Special Weather Statement	PSR		29 min
Jul 21, 3:51 PM MST	Flash Flood Warning Considerable damage threat	PSR	Maricopa	4 hr
Jul 21, 3:53 PM MST	Severe Thunderstorm Warning	PSR	Maricopa	37 min
Jul 21, 3:55 PM MST	Special Weather Statement	PSR	Maricopa	50 min
Jul 21, 4:01 PM MST	Severe Thunderstorm Warning	PSR	Maricopa	29 min
Jul 21, 4:11 PM MST	Special Weather Statement	PSR	La Paz	49 min
Jul 21, 4:28 PM MST	Special Weather Statement	PSR	Maricopa	47 min
Jul 21, 4:32 PM MST	Special Weather Statement	PSR		28 min
Jul 21, 4:55 PM MST	Flash Flood Warning Considerable damage threat	PSR	La Paz	4 hr
Jul 21, 4:59 PM MST	Special Weather Statement	PSR		46 min

Nearby

Flash Flood Warnings in Arizona, 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.