Alert archive / Arizona / Flash Flood Warnings in 2021

Flash Flood Warning 160, NWS Phoenix, AZ

August 12, 2021Maricopa County, Arizona

NWS Phoenix, AZ issued this flash flood warning at Aug 12, 2021, 7:00 AM MST for Maricopa County, Arizona. It was in force for 4 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, 7:00 AM MST (14:00 UTC)
Expired: Aug 12, 2021, 11:00 AM 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), 80 km from the middle of the area, began a volume at 14:01 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, 9:50 AM MST	FLASH FLOOD	6 N Deer Valley, AZ	ROAD CLOSURE DUE TO HIGH FLOWS IN SKUNK CREEK. MARICOPA COUNTY FLOOD CONTROL STREAM GAGE LOCATED UPSTREAM NEAR CAREFREE HIGHWAY EXCEEDED ALARM STAGE. TIMING BASED ON TRAVEL TIME INFORMATION PROVIDED BY MARICOPA COUNTY FLOOD CONTROL.

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, 2.0 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: 1266 J/kg
Mixed-layer CIN: -27 J/kg
Mixed-layer LCL: 865 m above ground
0-6 km bulk shear: 9 kt
0-1 km storm-relative helicity: 57 m²/s²
0-3 km storm-relative helicity: 99 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

504 
WGUS55 KPSR 121400
FFWPSR
AZC013-121800-
/O.NEW.KPSR.FF.W.0160.210812T1400Z-210812T1800Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Phoenix AZ
700 AM MST Thu Aug 12 2021

The National Weather Service in Phoenix has issued a

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

* Until 1100 AM MST.

* At 700 AM 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 of 
  0.5 to 1 inch are possible in the warned area. 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...
  Phoenix, Glendale, Peoria, Surprise, New River, Sun City West, 
  Cave Creek, Deer Valley Airport, Vistancia and Anthem.

This includes the following highways...
	AZ Route 303 between mile markers 121 and 130.
	AZ Route 74 between mile markers 13 and 22.
	AZ Interstate 17 between mile markers 216 and 225.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3388 11228 3390 11223 3402 11212 3400 11191
      3397 11196 3372 11208 3367 11208 3369 11240
      3385 11243 3385 11237

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

$$

INS

2 follow-up statements

331 
WGUS75 KPSR 121512
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
812 AM MST Thu Aug 12 2021

AZC013-121800-
/O.CON.KPSR.FF.W.0160.000000T0000Z-210812T1800Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
812 AM MST Thu Aug 12 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 11 AM MST THIS 
MORNING FOR MARICOPA COUNTY...

At 812 AM 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. 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...
  Phoenix, Glendale, Peoria, Surprise, New River, Sun City West, 
  Cave Creek, Deer Valley Airport, Vistancia and Anthem.

This includes the following highways...
	AZ Route 303 between mile markers 121 and 130.
	AZ Route 74 between mile markers 13 and 22.
	AZ Interstate 17 between mile markers 216 and 225.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3388 11228 3390 11223 3402 11212 3400 11191
      3397 11196 3372 11208 3367 11208 3369 11240
      3385 11243 3385 11237

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

$$

INS

073 
WGUS75 KPSR 121802
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
1102 AM MST Thu Aug 12 2021

AZC013-121812-
/O.EXP.KPSR.FF.W.0160.000000T0000Z-210812T1800Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
1102 AM MST Thu Aug 12 2021

...FLASH FLOOD WARNING HAS EXPIRED FOR 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 3388 11228 3390 11223 3402 11212 3400 11191
      3397 11196 3372 11208 3367 11208 3369 11240
      3385 11243 3385 11237

$$

INS

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 11, 5:03 PM MST	Severe Thunderstorm Warning	PSR	Maricopa	42 min
Aug 11, 5:14 PM MST	Flash Flood Warning Considerable damage threat	PSR	Maricopa	3 hr
Aug 11, 5:14 PM MST	Special Weather Statement	PSR	Maricopa	46 min
Aug 11, 5:30 PM MST	Flash Flood Warning	PSR	Maricopa	2 hr
Aug 11, 5:30 PM MST	Severe Thunderstorm Warning	PSR	Maricopa, Pinal	45 min
Aug 11, 5:39 PM MST	Flash Flood Warning Considerable damage threat	PSR	Maricopa	3 hr
Aug 11, 5:49 PM MST	Special Weather Statement	PSR		41 min
Aug 11, 5:57 PM MST	Flash Flood Warning Considerable damage threat	PSR	Maricopa	6 hr
Aug 11, 6:07 PM MST	Dust Storm Warning	PSR	Maricopa, Pinal	53 min
Aug 11, 6:12 PM MST	Severe Thunderstorm Warning	PSR	Maricopa, Pinal	48 min
Aug 11, 6:19 PM MST	Severe Thunderstorm Warning	PSR	Maricopa	41 min
Aug 11, 6:20 PM MST	Flash Flood Warning Considerable damage threat	PSR	Maricopa	4 hr
Aug 11, 6:40 PM MST	Flash Flood Warning	PSR	Maricopa	4 hr
Aug 11, 7:02 PM MST	Special Weather Statement	PSR		58 min
Aug 11, 7:11 PM MST	Special Weather Statement	PSR		64 min
Aug 11, 7:26 PM MST	Flash Flood Warning Considerable damage threat	PSR	La Paz	3 hr
Aug 11, 7:53 PM MST	Special Weather Statement	PSR	La Paz	37 min
Aug 12, 2:00 AM MST	Special Weather Statement	PSR		45 min
Aug 12, 2:42 AM MST	Flash Flood Warning Considerable damage threat	PSR	Gila, Maricopa	4 hr
Aug 12, 2:45 AM MST	Areal Flood Advisory	PSR	Maricopa	3 hr
Aug 12, 3:34 AM MST	Areal Flood Advisory	PSR	Maricopa	3 hr
Aug 12, 4:16 AM MST	Flash Flood Warning Considerable damage threat	PSR	Maricopa	4 hr
Aug 12, 4:33 AM MST	Flash Flood Warning Considerable damage threat	PSR	Maricopa	4 hr
Aug 12, 5:17 AM MST	Flash Flood Warning Considerable damage threat	PSR	Maricopa	6 hr
Aug 12, 6:04 AM MST	Flash Flood Warning Considerable damage threat	PSR	Maricopa	4 hr
Aug 12, 6:21 AM MST	Areal Flood Advisory	PSR	Maricopa	46 min
Aug 12, 10:09 AM MST	Areal Flood Warning	PSR	Gila	8 hr
Aug 12, 10:46 AM MST	Areal Flood Warning	PSR	Maricopa	15 hr
Aug 12, 1:30 PM MST	Flash Flood Watch	PSR	Gila, Maricopa, Pinal	5 days
Aug 12, 2:11 PM MST	Special Weather Statement	PSR	La Paz	34 min
Aug 12, 2:30 PM MST	Areal Flood Advisory	PSR	Maricopa	3 hr
Aug 12, 2:45 PM MST	Areal Flood Advisory	PSR	La Paz	3 hr
Aug 12, 2:54 PM MST	Flash Flood Warning Considerable damage threat	PSR	La Paz, Maricopa	4 hr
Aug 12, 3:11 PM MST	Flash Flood Warning Considerable damage threat	PSR	Maricopa	5 hr
Aug 12, 3:34 PM MST	Special Weather Statement	PSR		41 min
Aug 12, 4:14 PM MST	Areal Flood Advisory	PSR	Maricopa, Yuma	3 hr

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.