Alert archive / Arizona / Flash Flood Warnings in 2021

Flash Flood Warning 154, NWS Tucson, AZ

August 28, 2021Pima County, Arizona

NWS Tucson, AZ issued this flash flood warning at Aug 28, 2021, 4:26 PM MST for Pima County, Arizona. It was in force for 2 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 28, 2021, 4:26 PM MST (23:26 UTC)
Expired: Aug 28, 2021, 6:30 PM MST
In force: 2 hr
Issued by: NWS Tucson, AZ
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

County Pima County, AZ

The radar

The Tucson radar (KEMX), 70 km from the middle of the area, began a volume at 23:27 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

Tuscon, AZ (KTUS), launched 12:00Z, 11.4 hours before the alert went out and 66 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: 21 J/kg
Mixed-layer CIN: -393 J/kg
Mixed-layer LCL: 2964 m above ground
0-6 km bulk shear: 9 kt
0-1 km storm-relative helicity: -35 m²/s²
0-3 km storm-relative helicity: 65 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.7

Open this sounding in Storm Lab

The text

As transmitted.

143 
WGUS55 KTWC 282326
FFWTWC
AZC019-290130-
/O.NEW.KTWC.FF.W.0154.210828T2326Z-210829T0130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Tucson AZ
426 PM MST Sat Aug 28 2021

The National Weather Service in Tucson has issued a

* Flash Flood Warning for...
  Southeastern Pima County in southeastern Arizona...

* Until 630 PM MST.

* At 426 PM MST, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Up to 1 inch of rain has 
  fallen. Additional rainfall amounts up to 1 inch are possible in 
  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...
  mainly rural areas of Southeastern Pima County north and northwest 
  of Arivaca.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

LAT...LON 3166 11126 3163 11129 3163 11144 3168 11145
      3174 11146 3183 11141 3179 11122 3172 11121

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

$$

CC

2 follow-up statements

970 
WGUS75 KTWC 290010
FFSTWC

Flash Flood Statement
National Weather Service Tucson AZ
510 PM MST Sat Aug 28 2021

AZC019-290130-
/O.CON.KTWC.FF.W.0154.000000T0000Z-210829T0130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Pima AZ-
510 PM MST Sat Aug 28 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 630 PM MST THIS 
EVENING FOR SOUTHEASTERN PIMA COUNTY...

At 510 PM MST, Doppler radar indicated between 1 and 2 inches of 
rain had fallen along and north of Arivaca Road over the past hour. 
This will result in flash flooding, especially along Arivaca Creek, 
Las Guijas Wash and Arroyo Seco washes that all drain into the 
Puertocito and Altar Washes.

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...
  mainly rural areas of Southeastern Pima County

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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 3166 11126 3163 11129 3163 11144 3168 11145
      3174 11146 3183 11141 3179 11122 3172 11121

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

$$

CWR

744 
WGUS75 KTWC 290128
FFSTWC

Flash Flood Statement
National Weather Service Tucson AZ
628 PM MST Sat Aug 28 2021

AZC019-290138-
/O.EXP.KTWC.FF.W.0154.000000T0000Z-210829T0130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Pima AZ-
628 PM MST Sat Aug 28 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 630 PM MST THIS EVENING FOR 
SOUTHEASTERN PIMA COUNTY...

The heavy rain ended over an hour ago and waters should have receded 
at this time. Flooding is no longer expected to pose a threat. 
Please continue to heed remaining road closures.

LAT...LON 3166 11126 3163 11129 3163 11144 3168 11145
      3174 11146 3183 11141 3179 11122 3172 11121

$$

CC

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 27, 5:01 PM MST	Special Weather Statement	TWC		44 min
Aug 27, 5:04 PM MST	Areal Flood Advisory	TWC	Pima	2 hr
Aug 27, 5:27 PM MST	Special Weather Statement	TWC		33 min
Aug 28, 3:54 AM MST	Areal Flood Advisory	TWC	Pima	3 hr
Aug 28, 2:34 PM MST	Special Weather Statement	TWC	Santa Cruz	41 min
Aug 28, 2:42 PM MST	Special Weather Statement	TWC	Santa Cruz	48 min
Aug 28, 3:13 PM MST	Severe Thunderstorm Warning	TWC	Pima	47 min
Aug 28, 3:32 PM MST	Areal Flood Advisory	TWC	Pima	118 min
Aug 28, 3:49 PM MST	Special Weather Statement	TWC	Santa Cruz	41 min
Aug 28, 3:53 PM MST	Dust Storm Warning	TWC	Pima	52 min
Aug 28, 3:57 PM MST	Flash Flood Warning	TWC	Santa Cruz	108 min
Aug 28, 3:58 PM MST	Severe Thunderstorm Warning	TWC	Pima	62 min
Aug 28, 4:03 PM MST	Flash Flood Warning Considerable damage threat	TWC	Pima	117 min
Aug 28, 4:06 PM MST	Special Weather Statement	TWC		39 min
Aug 28, 4:14 PM MST	Areal Flood Advisory	TWC	Pima	2 hr
Aug 28, 4:24 PM MST	Severe Thunderstorm Warning	TWC	Pima	51 min
Aug 28, 4:26 PM MST	Severe Thunderstorm Warning	TWC	Pima	34 min
Aug 28, 4:31 PM MST	Flash Flood Warning Considerable damage threat	TWC	Pima	119 min
Aug 28, 4:34 PM MST	Areal Flood Advisory	TWC	Graham, Pinal	116 min
Aug 28, 4:37 PM MST	Severe Thunderstorm Warning	TWC	Pinal	38 min
Aug 28, 4:47 PM MST	Dust Storm Warning	TWC	Pima, Pinal	118 min
Aug 28, 4:58 PM MST	Severe Thunderstorm Warning	TWC	Pima, Pinal	62 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.