Alert archive / Arizona / Flash Flood Warnings in 2021

Flash Flood Warning 110, NWS Phoenix, AZ

July 29, 2021Maricopa County, Arizona

NWS Phoenix, AZ issued this flash flood warning at Jul 29, 2021, 6:17 PM MST for Maricopa County, Arizona. 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: Jul 29, 2021, 6:17 PM MST (01:17 UTC)
Expired: Jul 29, 2021, 9:04 PM MST
In force: 3 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), 72 km from the middle of the area, began a volume at 01:20 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 29, 8:20 PM MST	FLASH FLOOD	4 N Cave Creek, AZ	* DELAYED REPORT * USGS STREAMGAUGE #09512280 CAVE CREEK BELOW COTTONWOOD CREEK NEAR CAVE CREEK REACHED AND EXCEEDED ACTION STAGE. THIS GAUGE MEASURED AN APPROXIMATELY 5 FT. INCREASE DURING A 20 MINUTE PERIOD.

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 00:00Z, 1.3 hours before the alert went out and 53 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: 237 J/kg
Mixed-layer CIN: -43 J/kg
Mixed-layer LCL: 3197 m above ground
0-6 km bulk shear: 14 kt
0-1 km storm-relative helicity: 7 m²/s²
0-3 km storm-relative helicity: 2 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

470 
WGUS55 KPSR 300117
FFWPSR
AZC013-300545-
/O.NEW.KPSR.FF.W.0110.210730T0117Z-210730T0545Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Phoenix AZ
617 PM MST Thu Jul 29 2021

The National Weather Service in Phoenix has issued a

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

* Until 1045 PM MST.

* At 617 PM MST, Doppler radar and automated stream gauges indicated 
  a rapid rise along upper portions of Cave Creek. Cave Creek at 
  Ashdale has exceeded alarm stage and neared bankfull stage. 
  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...
  Scottsdale, New River, Cave Creek, Carefree and Seven Springs.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3402 11190 3400 11179 3389 11183 3384 11189
      3381 11196 3381 11201 3385 11202

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

$$

MS

1 follow-up statement

606 
WGUS75 KPSR 300404
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
904 PM MST Thu Jul 29 2021

AZC013-300414-
/O.CAN.KPSR.FF.W.0110.000000T0000Z-210730T0545Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
904 PM MST Thu Jul 29 2021

...FLASH FLOOD WARNING IS CANCELLED FOR MARICOPA COUNTY...

Flood waters in Cave Creek have receded. Flooding is no longer 
expected to pose a threat. Please continue to heed remaining road 
closures.

LAT...LON 3402 11190 3400 11179 3389 11183 3384 11189
      3381 11196 3381 11201 3385 11202

$$

Hirsch

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 29, 8:02 PM MST	Flash Flood Warning Considerable damage threat	PSR	Gila	6 hr
Jul 30, 7:28 AM MST	Areal Flood Warning	PSR	Gila	13 hr
Jul 30, 12:36 PM MST	Special Weather Statement	PSR	La Paz	24 min
Jul 30, 1:03 PM MST	Special Weather Statement	PSR		27 min
Jul 30, 1:19 PM MST	Areal Flood Advisory	PSR	La Paz	3 hr
Jul 30, 2:24 PM MST	Special Weather Statement	PSR		36 min
Jul 30, 2:59 PM MST	Special Weather Statement	PSR		31 min
Jul 30, 4:43 PM MST	Special Weather Statement	PSR		32 min
Jul 30, 4:50 PM MST	Flash Flood Warning Considerable damage threat	PSR	Gila	69 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.