Alert archive / Arizona / Flash Flood Warnings in 2021

Flash Flood Warning 251, NWS Phoenix, AZ

September 24, 2021Maricopa County, Arizona

NWS Phoenix, AZ issued this flash flood warning at Sep 24, 2021, 8:27 AM MST for Maricopa County, Arizona. It was in force for 4 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: Sep 24, 2021, 8:27 AM MST (15:27 UTC)
Expired: Sep 24, 2021, 12:30 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), 94 km from the middle of the area, began a volume at 15:28 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.

The nearest sounding before it

Tuscon, AZ (KTUS), launched 12:00Z, 3.5 hours before the alert went out and 179 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: 1 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1819 m above ground
0-6 km bulk shear: 15 kt
0-1 km storm-relative helicity: -39 m²/s²
0-3 km storm-relative helicity: -53 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

207 
WGUS55 KPSR 241527
FFWPSR
AZC013-241930-
/O.NEW.KPSR.FF.W.0251.210924T1527Z-210924T1930Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Phoenix AZ
827 AM MST Fri Sep 24 2021

The National Weather Service in Phoenix has issued a

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

* Until 1230 PM MST.

* At 827 AM MST, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1 and 1.5 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.

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

* Some locations that will experience flash flooding include...
  Gila Bend, Estrella, Bosque, Sonoran National Monument, Gila Bend 
  Auxiliary Field and Big Horn.

This includes the following highways...
	AZ Route 238 near mile marker 1...and
	between mile markers 10 and 18.
	AZ Route 85 near mile marker 1...and
	between mile markers 119 and 126...and
	near mile marker 2.
	AZ Interstate 8 between mile markers 112 and 121.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3284 11235 3283 11279 3290 11280 3301 11281
      3303 11264 3305 11234

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

$$

INS

1 follow-up statement

705 
WGUS75 KPSR 241729
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
1029 AM MST Fri Sep 24 2021

AZC013-241930-
/O.CON.KPSR.FF.W.0251.000000T0000Z-210924T1930Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
1029 AM MST Fri Sep 24 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 1230 PM MST THIS 
AFTERNOON FOR MARICOPA COUNTY...

At 1029 AM MST, Doppler radar indicated thunderstorms producing 
heavy rain across the warned area. Between 1 and 1.5 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 along State Route 238.

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

SOURCE...Radar.

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

Some locations that will experience flash flooding include...
  Gila Bend, Estrella, Bosque, Sonoran National Monument, Gila Bend 
  Auxiliary Field and Big Horn.

This includes the following highways...
	AZ Route 238 near mile marker 1...and
	between mile markers 10 and 18.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3284 11235 3283 11279 3290 11280 3301 11281
      3303 11264 3305 11234

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

$$

MS

The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 23, 5:46 PM MST	Special Weather Statement	PSR	Pinal	29 min
Sep 24, 6:13 AM MST	Areal Flood Advisory	PSR	Maricopa	3 hr
Sep 24, 6:39 AM MST	Special Weather Statement	PSR	Maricopa	51 min
Sep 24, 6:57 AM MST	Areal Flood Advisory	PSR	Maricopa	3 hr
Sep 24, 7:06 AM MST	Special Weather Statement	PSR		24 min
Sep 24, 7:37 AM MST	Areal Flood Advisory	PSR	Maricopa	3 hr
Sep 24, 8:11 AM MST	Special Weather Statement	PSR	Maricopa	34 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.