Alert archive / Arizona / Flash Flood Warnings in 2021

Flash Flood Warning 8, NWS Phoenix, AZ

July 1, 2021Maricopa County, Arizona

NWS Phoenix, AZ issued this flash flood warning at Jul 1, 2021, 9:37 PM 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: Jul 1, 2021, 9:37 PM MST (04:37 UTC)
Expired: Jul 2, 2021, 1:30 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), 50 km from the middle of the area, began a volume at 04:37 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, 4.6 hours before the alert went out and 64 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: 140 J/kg
Mixed-layer CIN: -50 J/kg
Mixed-layer LCL: 3255 m above ground
0-6 km bulk shear: 3 kt
0-1 km storm-relative helicity: -6 m²/s²
0-3 km storm-relative helicity: 44 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

406 
WGUS55 KPSR 020437
FFWPSR
AZC013-020830-
/O.NEW.KPSR.FF.W.0008.210702T0437Z-210702T0830Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Phoenix AZ
937 PM MST Thu Jul 1 2021

The National Weather Service in Phoenix has issued a

* Flash Flood Warning for...
  The Bush Fire burn scar in...
  Maricopa County in south central Arizona...

* Until 130 AM MST.

* At 937 PM MST, Doppler radar indicated thunderstorms producing 
  heavy rain over the Bush Fire Burn Scar. Between 0.5 and 1.25 
  inches of rain has fallen. Additional rainfall amounts up to 0.5 
  inches are possible in the warned area. Flash flooding is ongoing 
  or expected to begin shortly.

Excessive rainfall over the burn scar will result in debris flow 
moving through the Alder Creek toward Apache Lake. The debris flow 
can consist of rock, mud, vegetation and other loose materials.

  HAZARD...Life threatening flash flooding. Thunderstorms
           producing flash flooding in and around the Bush Fire
           Burn Scar.

  SOURCE...Radar.

  IMPACT...Life threatening flash flooding of areas in and around
           the Bush Fire Burn Scar.

* Some locations that will experience flash flooding include...
  Four Peaks.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Move away from recently burned areas. Life-threatening flooding of 
creeks, roads and normally dry arroyos is likely. The heavy rains 
will likely trigger rockslides, mudslides and debris flows in steep 
terrain, especially in and around these areas.

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

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 3364 11128 3361 11128 3359 11128 3359 11132
      3359 11133 3359 11134 3358 11135 3360 11137
      3360 11138 3363 11138 3365 11137 3366 11137
      3368 11137 3368 11135 3369 11133 3368 11132
      3367 11130 3366 11129 3365 11129

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

$$

Iniguez

2 follow-up statements

600 
WGUS75 KPSR 020555
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
1055 PM MST Thu Jul 1 2021

AZC013-020830-
/O.CON.KPSR.FF.W.0008.000000T0000Z-210702T0830Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
1055 PM MST Thu Jul 1 2021

...FLASH FLOOD WARNING FOR THE BUSH FIRE BURN SCAR REMAINS IN EFFECT 
UNTIL 130 AM MST FRIDAY FOR MARICOPA COUNTY...

At 1055 PM MST, Doppler radar indicated thunderstorms produced heavy 
rain of 0.5 to 1.25 inches over the Bush Fire Burn Scar. Flash 
flooding is ongoing or expected to begin shortly.

Excessive rainfall over the burn scar will result in debris flow 
moving through the Alder Creek. The debris flow can consist of rock, 
mud, vegetation and other loose materials.

HAZARD...Life threatening flash flooding. Thunderstorms producing
         flash flooding in and around the Bush Fire Burn Scar.

SOURCE...Radar.

IMPACT...Life threatening flash flooding of areas in and around
         the Bush Fire Burn Scar.

Some locations that will experience flash flooding include...
  Four Peaks.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Move away from recently burned areas. Life-threatening flooding of 
creeks, roads and normally dry arroyos is likely. The heavy rains 
will likely trigger rockslides, mudslides and debris flows in steep 
terrain, especially in and around these areas.

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

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 3364 11128 3361 11128 3359 11128 3359 11132
      3359 11133 3359 11134 3358 11135 3360 11137
      3360 11138 3363 11138 3365 11137 3366 11137
      3368 11137 3368 11135 3369 11133 3368 11132
      3367 11130 3366 11129 3365 11129

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

$$

Iniguez

532 
WGUS75 KPSR 020825
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
125 AM MST Fri Jul 2 2021

AZC013-020835-
/O.EXP.KPSR.FF.W.0008.000000T0000Z-210702T0830Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
125 AM MST Fri Jul 2 2021

...FLASH FLOOD WARNING FOR THE BUSH FIRE BURN SCAR WILL EXPIRE AT 
130 AM MST EARLY 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 3364 11128 3361 11128 3359 11128 3359 11132
      3359 11133 3359 11134 3358 11135 3360 11137
      3360 11138 3363 11138 3365 11137 3366 11137
      3368 11137 3368 11135 3369 11133 3368 11132
      3367 11130 3366 11129 3365 11129

$$

JS

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 1, 8:16 PM MST	Flash Flood Warning Considerable damage threat	PSR	Gila	4 hr
Jul 1, 9:57 PM MST	Special Weather Statement	PSR		48 min
Jul 1, 10:22 PM MST	Flash Flood Warning Considerable damage threat	PSR	Maricopa	4 hr
Jul 2, 4:00 PM MST	Flash Flood Warning Considerable damage threat	PSR	Gila	4 hr
Jul 2, 4:12 PM MST	Special Weather Statement	PSR		33 min
Jul 2, 4:50 PM MST	Special Weather Statement	PSR	Gila	25 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.