Alert archive / Arizona / Flash Flood Warnings in 2021

Flash Flood Warning 132, NWS Phoenix, AZ

August 9, 2021Maricopa County, Arizona

NWS Phoenix, AZ issued this flash flood warning at Aug 9, 2021, 11:51 PM MST for Maricopa County, Arizona. It was in force for 8 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: Aug 9, 2021, 11:51 PM MST (06:51 UTC)
Expired: Aug 10, 2021, 7:30 AM MST
In force: 8 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), 77 km from the middle of the area, began a volume at 06:50 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, 6.9 hours before the alert went out and 63 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: 413 J/kg
Mixed-layer CIN: -229 J/kg
Mixed-layer LCL: 1911 m above ground
0-6 km bulk shear: 10 kt
0-1 km storm-relative helicity: 88 m²/s²
0-3 km storm-relative helicity: 136 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

817 
WGUS55 KPSR 100651
FFWPSR
AZC013-101100-
/O.NEW.KPSR.FF.W.0132.210810T0651Z-210810T1100Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Phoenix AZ
1151 PM MST Mon Aug 9 2021

The National Weather Service in Phoenix has issued a

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

* Until 400 AM MST.

* At 1151 PM MST, Doppler radar indicated thunderstorms producing 
  heavy rain across 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...
  Primarily State Route 238 between Gila Bend and Maricopa. Very 
  little precipitation is needed for flash flooding at low water 
  crossings across SR 238.

This includes the following highways...
	AZ Route 238 between mile markers 10 and 19.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

Be aware of your surroundings and do not drive on flooded roads.

In hilly terrain there are hundreds of low water crossings which are 
potentially dangerous in heavy rain. Do not attempt to cross flooded 
roads. Find an alternate route.

&&

LAT...LON 3309 11224 3304 11222 3301 11237 3298 11243
      3295 11267 3297 11267 3299 11256 3301 11251
      3302 11246 3301 11244 3306 11234

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

$$

AD

6 follow-up statements

531 
WGUS75 KPSR 100751
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
1251 AM MST Tue Aug 10 2021

AZC013-101100-
/O.CON.KPSR.FF.W.0132.000000T0000Z-210810T1100Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
1251 AM MST Tue Aug 10 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 4 AM MST EARLY THIS 
MORNING FOR MARICOPA COUNTY...

At 1251 AM MST, Doppler radar indicated thunderstorms producing 
heavy rain across the warned area. Flash flooding is ongoing.

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, Sonoran National Monument, Bosque and Mobile.

This includes the following highways...
	AZ Route 238 between mile markers 10 and 19.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

Be aware of your surroundings and do not drive on flooded roads.

In hilly terrain there are hundreds of low water crossings which are 
potentially dangerous in heavy rain. Do not attempt to cross flooded 
roads. Find an alternate route.

&&

LAT...LON 3309 11224 3304 11222 3301 11237 3298 11243
      3295 11267 3297 11267 3299 11256 3301 11251
      3302 11246 3301 11244 3306 11234

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

$$

JS

666 
WGUS55 KPSR 100923
FFWPSR
AZC013-101300-
/O.EXT.KPSR.FF.W.0132.000000T0000Z-210810T1300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Phoenix AZ
223 AM MST Tue Aug 10 2021

The National Weather Service in Phoenix has extended the

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

* Until 600 AM MST.

* At 223 AM MST, Doppler radar indicated thunderstorms producing 
  heavy rain across 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, Sonoran National Monument, Bosque and Mobile.

This includes the following highways...
	AZ Route 238 between mile markers 10 and 19.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

Be aware of your surroundings and do not drive on flooded roads.

In hilly terrain there are hundreds of low water crossings which are 
potentially dangerous in heavy rain. Do not attempt to cross flooded 
roads. Find an alternate route.

&&

LAT...LON 3309 11224 3304 11222 3301 11237 3298 11243
      3295 11267 3297 11267 3299 11256 3301 11251
      3302 11246 3301 11244 3306 11234

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

$$

AD

405 
WGUS75 KPSR 100951
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
251 AM MST Tue Aug 10 2021

AZC013-101300-
/O.CON.KPSR.FF.W.0132.000000T0000Z-210810T1300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
251 AM MST Tue Aug 10 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 6 AM MST EARLY THIS 
MORNING FOR MARICOPA COUNTY...

At 251 AM MST, Doppler radar indicated thunderstorms producing heavy 
rain across the warned area. Flash flooding is ongoing.

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, Sonoran National Monument, Bosque and Mobile.

This includes the following highways...
	AZ Route 238 between mile markers 10 and 19.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

Be aware of your surroundings and do not drive on flooded roads.

In hilly terrain there are hundreds of low water crossings which are 
potentially dangerous in heavy rain. Do not attempt to cross flooded 
roads. Find an alternate route.

&&

LAT...LON 3309 11224 3304 11222 3301 11237 3298 11243
      3295 11267 3297 11267 3299 11256 3301 11251
      3302 11246 3301 11244 3306 11234

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

$$

JS

097 
WGUS75 KPSR 101124
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
424 AM MST Tue Aug 10 2021

AZC013-101300-
/O.CON.KPSR.FF.W.0132.000000T0000Z-210810T1300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
424 AM MST Tue Aug 10 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 6 AM MST EARLY THIS 
MORNING FOR MARICOPA COUNTY...

At 424 AM MST, Doppler radar indicated new thunderstorms in the 
warned area.

HAZARD...Life threatening flash flooding. Thunderstorms capable
         of 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...
Primarily State Route 238 between Gila Bend and Maricopa. Very 
little precipitation is needed for flash flooding at low water 
crossings across SR 238.

This includes the following highways...
	AZ Route 238 between mile markers 10 and 19.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

Be aware of your surroundings and do not drive on flooded roads.

In hilly terrain there are hundreds of low water crossings which are 
potentially dangerous in heavy rain. Do not attempt to cross flooded 
roads. Find an alternate route.

&&

LAT...LON 3309 11224 3304 11222 3301 11237 3298 11243
      3295 11267 3297 11267 3299 11256 3301 11251
      3302 11246 3301 11244 3306 11234

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

$$

AD

732 
WGUS55 KPSR 101223
FFWPSR
AZC013-101430-
/O.EXT.KPSR.FF.W.0132.000000T0000Z-210810T1430Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Phoenix AZ
523 AM MST Tue Aug 10 2021

The National Weather Service in Phoenix has extended the

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

* Until 730 AM MST.

* At 523 AM MST, Doppler radar indicated thunderstorms producing 
  heavy rain on the basins that flow towards State Route 238. 
  Historically, this basin takes very little rainfall to cause flash 
  flooding at low water crossing over SR 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...
  Primarily State Route 238 between Gila Bend and Maricopa. Very 
  little precipitation is needed for flash flooding at low water 
  crossings across SR 238.

This includes the following highways...
	AZ Route 238 between mile markers 10 and 19.

While flood reports have yet to come in, estimated and nearby 
rainfall amounts meet historically typical levels needed to flood 
SR-238. This highway is remote and very prone to flooding with even 
just very little rainfall.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be aware of your surroundings and do not drive on flooded roads.

In hilly terrain there are hundreds of low water crossings which are 
potentially dangerous in heavy rain. Do not attempt to cross flooded 
roads. Find an alternate route.

&&

LAT...LON 3309 11224 3304 11222 3301 11237 3298 11243
      3295 11267 3297 11267 3299 11256 3301 11251
      3302 11246 3301 11244 3306 11234

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

$$

AD

650 
WGUS75 KPSR 101428
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
728 AM MST Tue Aug 10 2021

AZC013-101438-
/O.EXP.KPSR.FF.W.0132.000000T0000Z-210810T1430Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
728 AM MST Tue Aug 10 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 730 AM MST THIS MORNING 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 3309 11224 3304 11222 3301 11237 3298 11243
      3295 11267 3297 11267 3299 11256 3301 11251
      3302 11246 3301 11244 3306 11234

$$

AD

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 9, 5:24 PM MST	Areal Flood Advisory	PSR	La Paz	3 hr
Aug 9, 5:44 PM MST	Special Weather Statement	PSR	La Paz	46 min
Aug 9, 6:22 PM MST	Special Weather Statement	PSR		38 min
Aug 9, 10:11 PM MST	Special Weather Statement	PSR	Gila	34 min
Aug 9, 10:40 PM MST	Flash Flood Warning Considerable damage threat	PSR	Gila	4 hr
Aug 10, 1:40 AM MST	Special Weather Statement	PSR	Maricopa	50 min
Aug 10, 1:54 AM MST	Special Weather Statement	PSR	Maricopa	51 min
Aug 10, 2:15 AM MST	Special Weather Statement	PSR	Maricopa	45 min
Aug 10, 2:23 AM MST	Areal Flood Advisory	PSR	Maricopa, Pinal	2 hr
Aug 10, 4:27 AM MST	Special Weather Statement	PSR	La Paz	48 min
Aug 10, 5:07 AM MST	Special Weather Statement	PSR	La Paz	53 min
Aug 10, 5:09 AM MST	Areal Flood Advisory	PSR	La Paz	2 hr
Aug 10, 5:52 AM MST	Areal Flood Advisory	PSR	Maricopa, Pinal	5 hr
Aug 10, 6:21 AM MST	Special Weather Statement	PSR	La Paz	39 min
Aug 10, 7:39 AM MST	Areal Flood Advisory	PSR	Maricopa, Pinal	3 hr
Aug 10, 8:00 AM MST	Flash Flood Warning Considerable damage threat	PSR	Maricopa	3 hr
Aug 10, 8:06 AM MST	Flash Flood Warning Considerable damage threat	PSR	Maricopa	4 hr
Aug 10, 8:30 AM MST	Flash Flood Warning Considerable damage threat	PSR	Maricopa, Pinal	7 hr
Aug 10, 9:54 AM MST	Areal Flood Advisory	PSR	La Paz	3 hr
Aug 10, 3:05 PM MST	Areal Flood Warning	PSR	Maricopa, Pinal	7 hr
Aug 10, 4:43 PM MST	Special Weather Statement	PSR		62 min
Aug 10, 4:44 PM MST	Special Weather Statement	PSR		61 min
Aug 10, 4:56 PM MST	Severe Thunderstorm Warning	PSR	Maricopa	49 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.