Alert archive / Arizona / Flash Flood Warnings in 2021

Flash Flood Warning 171, NWS Flagstaff, AZ

August 11, 2021Navajo County, Arizona

NWS Flagstaff, AZ issued this flash flood warning at Aug 11, 2021, 6:35 PM MDT for Navajo 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: Aug 11, 2021, 6:35 PM MDT (00:35 UTC)
Expired: Aug 11, 2021, 9:45 PM MDT
In force: 3 hr
Issued by: NWS Flagstaff, AZ
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

County Navajo County, AZ

The radar

The Flagstaff radar (KFSX), 129 km from the middle of the area, began a volume at 00:38 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

Flgstf/Belemont, AZ (KFGZ), launched 00:00Z, 0.6 hours before the alert went out and 154 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: 211 J/kg
Mixed-layer CIN: -67 J/kg
Mixed-layer LCL: 1027 m above ground
0-6 km bulk shear: 15 kt
0-1 km storm-relative helicity: -72 m²/s²
0-3 km storm-relative helicity: -71 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

058 
WGUS55 KFGZ 120035
FFWFGZ
AZC017-120345-
/O.NEW.KFGZ.FF.W.0171.210812T0035Z-210812T0345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Flagstaff AZ
535 PM MST Wed Aug 11 2021

The National Weather Service in Flagstaff has issued a

* Flash Flood Warning for...
  Navajo County in north central Arizona...

* Until 845 PM MST.

* At 533 PM MST, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1 and 1.5 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 low-water
           crossings, creeks, normally dry washes and roads.

* Some locations that will experience flash flooding include...
  Navajo Reservation including the area south and southwest of 
  Indian Wells extending out to 15 miles.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3541 11014 3539 11005 3528 10996 3520 11005
      3519 11011 3526 11019 3537 11021

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

$$

McCollum

1 follow-up statement

832 
WGUS75 KFGZ 120340
FFSFGZ

Flash Flood Statement
National Weather Service Flagstaff AZ
840 PM MST Wed Aug 11 2021

AZC017-120350-
/O.EXP.KFGZ.FF.W.0171.000000T0000Z-210812T0345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Navajo AZ-
840 PM MST Wed Aug 11 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 845 PM MST THIS EVENING FOR 
NAVAJO COUNTY...

The heavy rain has ended across the area south of Indian Wells. 
Flooding is no longer expected to pose a threat. Please heed road 
closures and avoid driving across flowing water on roads.

LAT...LON 3541 11014 3539 11005 3528 10996 3520 11005
      3519 11011 3526 11019 3537 11021

$$

McCollum

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 12, 6:36 AM MDT	Flash Flood Warning Considerable damage threat	FGZ	Gila	3 hr
Aug 12, 1:34 PM MDT	Special Weather Statement	FGZ	Yavapai	26 min
Aug 12, 1:43 PM MDT	Special Weather Statement	FGZ		32 min
Aug 12, 2:08 PM MDT	Special Weather Statement	FGZ		22 min
Aug 12, 2:29 PM MDT	Special Weather Statement	FGZ		31 min
Aug 12, 4:21 PM MDT	Special Weather Statement	FGZ	Yavapai	24 min
Aug 12, 4:41 PM MDT	Flash Flood Warning Considerable damage threat	FGZ	Coconino	6 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.