Alert archive / Arizona / Areal Flood Warnings in 2021

Areal Flood Warning 21, NWS Phoenix, AZ

August 18, 2021Maricopa County, Arizona

NWS Phoenix, AZ issued this areal flood warning at Aug 18, 2021, 7:20 PM MST for Maricopa County, Arizona. It was in force for 6 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 18, 2021, 7:20 PM MST (02:20 UTC)
Expired
Aug 19, 2021, 1:30 AM MST
In force
6 hr
Issued by
NWS Phoenix, AZ
Area
Storm-based polygon
Flood severity
None

County Maricopa County, AZ

The radar

The Phoenix radar (KIWA), 58 km from the middle of the area, began a volume at 02:24 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, 2.3 hours before the alert went out and 58 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-pSkew-T log-p diagram, Phoenix, AZ at 00:00Z on 2021-08-19Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 510 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Phoenix, AZ at 00:00Z on 2021-08-19The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 157 square meters per square second.1939Sfc1 km3 km6 km9 kmRMLM
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
510 J/kg
Mixed-layer CIN
-174 J/kg
Mixed-layer LCL
1692 m above ground
0-6 km bulk shear
24 kt
0-1 km storm-relative helicity
157 m²/s²
0-3 km storm-relative helicity
230 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.7

Open this sounding in Storm Lab

The text

As transmitted.

394 
WGUS45 KPSR 190220
FLWPSR

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Flood Warning
National Weather Service Phoenix AZ
720 PM MST Wed Aug 18 2021

AZC013-190530-
/O.NEW.KPSR.FA.W.0021.210819T0220Z-210819T0530Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
720 PM MST Wed Aug 18 2021

The National Weather Service in Phoenix has issued a

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

* Until 1030 PM MST.

* At 720 PM MST, Doppler radar indicated heavy rain due to 
  thunderstorms. Flooding is already occurring in the warned area.

* Some locations that will experience flooding include...
  Ballantine Trailhead, Round Valley, Sugarloaf Mountain, Sunflower, 
  Sycamore Creek and Fort McDowell.

Flooding is occurring along the Sycamore Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3398 11145 3391 11147 3385 11144 3375 11150
      3369 11153 3363 11160 3360 11169 3365 11168
      3370 11156 3384 11150 3400 11149

$$

CK
2 follow-up statements
189 
WGUS45 KPSR 190511
FLWPSR

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Flood Warning
National Weather Service Phoenix AZ
1011 PM MST Wed Aug 18 2021

AZC013-190830-
/O.EXT.KPSR.FA.W.0021.000000T0000Z-210819T0830Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
1011 PM MST Wed Aug 18 2021

The National Weather Service in Phoenix has extended the

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

* Until 130 AM MST.

* At 1011 PM MST, Doppler radar and automated rain gauges indicated 
  heavy rain due to thunderstorms. Flooding is already occurring in 
  the warned area.

* Some locations that will experience flooding include...
  Ballantine Trailhead, Round Valley, Sugarloaf Mountain, Sunflower, 
  Sycamore Creek and Fort McDowell.

Flooding is occurring along the Sycamore Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3398 11145 3391 11147 3385 11144 3375 11150
      3369 11153 3363 11160 3360 11169 3365 11168
      3370 11156 3384 11150 3400 11149

$$

CK
065 
WGUS85 KPSR 190827 RRB
FLSPSR

Flood Statement
National Weather Service Phoenix AZ
127 AM MST Thu Aug 19 2021

AZC013-190837-
/O.EXP.KPSR.FA.W.0021.000000T0000Z-210819T0830Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
127 AM MST Thu Aug 19 2021

...FLOOD WARNING WILL EXPIRE AT 130 AM MST EARLY THIS MORNING FOR 
MARICOPA COUNTY...

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

LAT...LON 3398 11145 3391 11147 3385 11144 3375 11150
      3369 11153 3363 11160 3360 11169 3365 11168
      3370 11156 3384 11150 3400 11149

$$

SDB

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 18, 5:13 PM MSTFlash Flood Warning Considerable damage threatPSRGila4 hr
Aug 18, 5:20 PM MSTSpecial Weather StatementPSRGila40 min
Aug 18, 5:25 PM MSTSevere Thunderstorm WarningPSRMaricopa, Pinal50 min
Aug 18, 5:34 PM MSTSpecial Weather StatementPSR41 min
Aug 18, 5:39 PM MSTFlash Flood Warning Considerable damage threatPSRGila4 hr
Aug 18, 5:40 PM MSTSpecial Weather StatementPSRMaricopa50 min
Aug 18, 5:43 PM MSTSevere Thunderstorm WarningPSRMaricopa32 min
Aug 18, 5:52 PM MSTSpecial Weather StatementPSR38 min
Aug 18, 6:09 PM MSTFlash Flood Warning Considerable damage threatPSRMaricopa, Pinal3 hr
Aug 18, 6:14 PM MSTFlash Flood Warning Considerable damage threatPSRMaricopa3 hr
Aug 18, 6:20 PM MSTFlash Flood Warning Considerable damage threatPSRGila4 hr
Aug 18, 6:36 PM MSTSpecial Weather StatementPSR39 min
Aug 18, 7:33 PM MSTAreal Flood WarningPSRMaricopa6 hr
Aug 18, 7:33 PM MSTAreal Flood WarningPSRMaricopa6 hr
Aug 18, 8:57 PM MSTAreal Flood WarningPSRMaricopa14 hr

Nearby

Areal Flood Warnings in Arizona, 2021Every areal 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.