Alert archive / Arizona / Flash Flood Warnings in 2021

Flash Flood Warning 241, NWS Phoenix, AZ

September 1, 2021Maricopa County, Arizona

NWS Phoenix, AZ issued this flash flood warning at Sep 1, 2021, 5:45 PM MST for Maricopa County, Arizona. It was in force for 3 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 1, 2021, 5:45 PM MST (00:45 UTC)
Expired: Sep 1, 2021, 8:47 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), 76 km from the middle of the area, began a volume at 00:48 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

Phoenix, AZ (KPSR), launched 00:00Z, 0.8 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: 518 J/kg
Mixed-layer CIN: -9 J/kg
Mixed-layer LCL: 1794 m above ground
0-6 km bulk shear: 21 kt
0-1 km storm-relative helicity: 17 m²/s²
0-3 km storm-relative helicity: 65 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

627 
WGUS55 KPSR 020045
FFWPSR
AZC013-020845-
/O.NEW.KPSR.FF.W.0241.210902T0045Z-210902T0845Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Phoenix AZ
545 PM MST Wed Sep 1 2021

The National Weather Service in Phoenix has issued a

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

* Until 145 AM MST Thursday.

* At 545 PM MST, Doppler radar indicated thunderstorms producing 
  heavy rain in New River. Between 0.5 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, particularly near New River, Deadman Wash and Skunk Creek.

  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...
  Phoenix, Scottsdale, New River, Cave Creek, Carefree, Desert 
  Mountain, Camp Creek, Vistancia, Anthem and Seven Springs.

This includes the following highways...
	AZ Route 303 between mile markers 123 and 132.
	AZ Route 74 between mile markers 19 and 28.
	AZ Interstate 17 between mile markers 218 and 227.

This includes the following streams and drainages...
  Grapevine Wash, Skunk Creek, Sheep Creek, Copper Camp Creek, 
  Galloway Wash, Lime Creek, Beardsley Canal, Camp Creek, Rodger 
  Creek, Little Squaw Creek, North Canyon Creek, Agua Fria River, 
  Verde River, Apache Wash, Tule Creek, Davenport Wash, Blue Wash, 
  Morgan City Wash, Indian Spring Wash, Seven Springs Wash, Cave 
  Creek, South Fork Sheep Creek, Deadman Creek, New River, 
  Cottonwood Creek and Deadman Wash.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3400 11154 3393 11157 3384 11168 3373 11183
      3371 11207 3370 11240 3389 11231 3388 11228
      3391 11224 3394 11223 3396 11224 3397 11220
      3404 11216 3405 11216 3400 11173

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

$$

Hirsch

2 follow-up statements

155 
WGUS75 KPSR 020128
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
628 PM MST Wed Sep 1 2021

AZC013-020845-
/O.CON.KPSR.FF.W.0241.000000T0000Z-210902T0845Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
628 PM MST Wed Sep 1 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 145 AM MST THURSDAY 
FOR MARICOPA COUNTY...

At 628 PM MST, Doppler radar indicated thunderstorms producing heavy 
rain across portions of northern Maricopa County. Between 0.5 and 
1.5 inches of rain have fallen. Additional rainfall amounts up to 
0.5 inches are possible in the warned area. Flash flooding is 
ongoing or expected to begin shortly, particularly near the Sears 
burn scar and Camp Creek.

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...
  Phoenix, Scottsdale, New River, Cave Creek, Carefree, Desert 
  Mountain, Camp Creek, Vistancia, Anthem and Seven Springs.

This includes the following highways...
	AZ Route 303 between mile markers 125 and 134.
	AZ Route 74 between mile markers 18 and 27.
	AZ Interstate 17 between mile markers 218 and 227.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Flooding is occurring or is imminent. It is important to know where 
you are relative to streams, rivers, or creeks which can become 
killers in heavy rains. Campers and hikers should avoid streams or 
creeks.

&&

LAT...LON 3400 11154 3393 11157 3384 11168 3373 11183
      3371 11207 3370 11240 3389 11231 3388 11228
      3391 11224 3394 11223 3396 11224 3397 11220
      3404 11216 3405 11216 3400 11173

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

$$

Hirsch

783 
WGUS75 KPSR 020347
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
847 PM MST Wed Sep 1 2021

AZC013-020357-
/O.CAN.KPSR.FF.W.0241.000000T0000Z-210902T0845Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
847 PM MST Wed Sep 1 2021

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

Flood waters have receded near New River. The heavy rain has ended. 
Flooding is no longer expected to pose a threat. Please continue to 
heed remaining road closures.

A Flash Flood Watch remains in effect until 500 AM MST Thursday for 
portions of south central Arizona and southwest Arizona.

LAT...LON 3400 11154 3393 11157 3384 11168 3373 11183
      3371 11207 3370 11240 3389 11231 3388 11228
      3391 11224 3394 11223 3396 11224 3397 11220
      3404 11216 3405 11216 3400 11173

$$

Hirsch

The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 1, 5:17 PM MST	Special Weather Statement	PSR		58 min
Sep 1, 7:18 PM MST	Flash Flood Warning Considerable damage threat	PSR	Gila, Maricopa	88 min
Sep 1, 9:35 PM MST	Areal Flood Advisory	PSR	Maricopa, Pinal	6 hr
Sep 1, 10:09 PM MST	Flash Flood Warning Considerable damage threat	PSR	Maricopa	5 hr
Sep 1, 11:09 PM MST	Areal Flood Advisory	PSR	Maricopa, Pinal	7 hr
Sep 2, 12:41 AM MST	Areal Flood Advisory	PSR	Maricopa, Pinal	3 hr
Sep 2, 1:52 AM MST	Areal Flood Advisory	PSR	Pinal	3 hr
Sep 2, 5:22 AM MST	Areal Flood Advisory	PSR	Pinal	4 hr
Sep 2, 6:11 AM MST	Areal Flood Advisory	PSR	Maricopa, Pinal	3 hr
Sep 2, 3:25 PM MST	Special Weather Statement	PSR	Maricopa	65 min
Sep 2, 3:51 PM MST	Areal Flood Advisory	PSR	Maricopa, Pinal	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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.