Alert archive / Arizona / Flash Flood Warnings in 2021

Flash Flood Warning 48, NWS Phoenix, AZ

July 20, 2021Maricopa County, Arizona

NWS Phoenix, AZ issued this flash flood warning at Jul 20, 2021, 3:55 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: Jul 20, 2021, 3:55 PM MST (22:55 UTC)
Expired: Jul 20, 2021, 7:00 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), 146 km from the middle of the area, began a volume at 22:56 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 12:00Z, 10.9 hours before the alert went out and 128 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: 1057 J/kg
Mixed-layer CIN: -177 J/kg
Mixed-layer LCL: 1907 m above ground
0-6 km bulk shear: 15 kt
0-1 km storm-relative helicity: 16 m²/s²
0-3 km storm-relative helicity: 32 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

270 
WGUS55 KPSR 202255
FFWPSR
AZC013-210200-
/O.NEW.KPSR.FF.W.0048.210720T2255Z-210721T0200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Phoenix AZ
355 PM MST Tue Jul 20 2021

The National Weather Service in Phoenix has issued a

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

* Until 700 PM MST.

* At 355 PM MST, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1.5 and 2.5 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.

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

* Some locations that will experience flash flooding include...
  Sentinel.

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.

&&

LAT...LON 3302 11306 3275 11297 3258 11298 3256 11308
      3262 11317 3276 11325 3284 11326 3293 11328
      3305 11315

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

$$

JS

2 follow-up statements

620 
WGUS75 KPSR 202343
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
443 PM MST Tue Jul 20 2021

AZC013-210200-
/O.CON.KPSR.FF.W.0048.000000T0000Z-210721T0200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
443 PM MST Tue Jul 20 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 7 PM MST THIS EVENING 
FOR MARICOPA COUNTY...

At 443 PM MST, Doppler radar indicated thunderstorms producing heavy 
rain across the warned area. Between 1.5 and 2.5 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.

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

Some locations that will experience flash flooding include...
  Sentinel.

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.

&&

LAT...LON 3302 11306 3275 11297 3258 11298 3256 11308
      3262 11317 3276 11325 3284 11326 3293 11328
      3305 11315

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

$$

JS

689 
WGUS75 KPSR 210157
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
657 PM MST Tue Jul 20 2021

AZC013-210207-
/O.EXP.KPSR.FF.W.0048.000000T0000Z-210721T0200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
657 PM MST Tue Jul 20 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 7 PM MST THIS EVENING FOR 
MARICOPA COUNTY...

Flooding is no longer expected to pose a threat. Please continue to 
heed remaining road closures.

LAT...LON 3302 11306 3275 11297 3258 11298 3256 11308
      3262 11317 3276 11325 3284 11326 3293 11328
      3305 11315

$$

JS

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 19, 6:20 PM MST	Special Weather Statement	PSR	La Paz	40 min
Jul 19, 6:52 PM MST	Flash Flood Warning Considerable damage threat	PSR	La Paz	2 hr
Jul 20, 1:33 PM MST	Special Weather Statement	PSR		42 min
Jul 20, 1:41 PM MST	Special Weather Statement	PSR		49 min
Jul 20, 2:02 PM MST	Areal Flood Advisory	PSR	Maricopa	3 hr
Jul 20, 2:17 PM MST	Special Weather Statement	PSR		43 min
Jul 20, 2:28 PM MST	Special Weather Statement	PSR		32 min
Jul 20, 2:37 PM MST	Special Weather Statement	PSR		53 min
Jul 20, 2:43 PM MST	Special Weather Statement	PSR		47 min
Jul 20, 2:57 PM MST	Special Weather Statement	PSR		48 min
Jul 20, 3:05 PM MST	Special Weather Statement	PSR		40 min
Jul 20, 3:08 PM MST	Special Weather Statement	PSR		52 min
Jul 20, 3:20 PM MST	Special Weather Statement	PSR	La Paz	40 min
Jul 20, 3:32 PM MST	Flash Flood Warning Considerable damage threat	PSR	La Paz, Maricopa	3 hr
Jul 20, 3:36 PM MST	Special Weather Statement	PSR		39 min
Jul 20, 3:47 PM MST	Special Weather Statement	PSR		43 min
Jul 20, 4:21 PM MST	Special Weather Statement	PSR		39 min
Jul 20, 4:23 PM MST	Special Weather Statement	PSR	La Paz	52 min
Jul 20, 4:30 PM MST	Special Weather Statement	PSR		45 min
Jul 20, 4:41 PM MST	Flash Flood Warning Considerable damage threat	PSR	La Paz	3 hr
Jul 20, 4:47 PM MST	Special Weather Statement	PSR	Gila	43 min
Jul 20, 4:53 PM MST	Areal Flood Advisory	PSR	La Paz	3 hr
Jul 20, 4:57 PM MST	Areal Flood Advisory	PSR	La Paz	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.