Alert archive / Arizona / Flash Flood Warnings in 2021

Flash Flood Warning 173, NWS Flagstaff, AZ

August 12, 2021Coconino County, Arizona

NWS Flagstaff, AZ issued this flash flood warning at Aug 12, 2021, 3:41 PM MST for Coconino 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 12, 2021, 3:41 PM MST (22:41 UTC)
Expired: Aug 12, 2021, 10:00 PM MST
In force: 6 hr
Issued by: NWS Flagstaff, AZ
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

County Coconino County, AZ

The radar

The Cedar City radar (KICX), 80 km from the middle of the area, began a volume at 22:44 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 12:00Z, 10.7 hours before the alert went out and 200 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: 40 J/kg
Mixed-layer CIN: -119 J/kg
Mixed-layer LCL: 1538 m above ground
0-6 km bulk shear: 3 kt
0-1 km storm-relative helicity: 53 m²/s²
0-3 km storm-relative helicity: 62 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.0

Open this sounding in Storm Lab

The text

As transmitted.

221 
WGUS55 KFGZ 122241
FFWFGZ
AZC005-130145-
/O.NEW.KFGZ.FF.W.0173.210812T2241Z-210813T0145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Flagstaff AZ
341 PM MST Thu Aug 12 2021

The National Weather Service in Flagstaff has issued a

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

* Until 645 PM MST.

* At 339 PM MST, Doppler radar indicated thunderstorms producing 
  heavy rain along Kanab Creek upstream of Fredonia. Between 0.5 and 
  1.5 inches of rain have fallen. Additional rainfall amounts of 0.5 
  to 1.5 inches 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 low-water
           crossings, creeks, normally dry washes and roads.

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

This includes the following highways...
	State Route 389 near mile marker 32.
	U.S. Highway 89A between mile markers 603 and 613.

This includes the following streams and drainages...
  Kanab Creek, Johnson Wash, Johnson Run, Lost Spring Wash, Wildcat 
  Canyon, Jacob Canyon and White Sage Wash.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Remain alert for flooding even in locations not receiving rain. 
Normally dry washes, slot canyons and creeks can become raging 
killer currents in a matter of minutes, even from distant rainfall.

&&

LAT...LON 3700 11234 3693 11238 3688 11247 3685 11259
      3686 11259 3687 11258 3689 11257 3691 11255
      3694 11255 3695 11253 3697 11253 3698 11254
      3700 11254

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

$$

Humphreys

2 follow-up statements

238 
WGUS55 KFGZ 122352
FFWFGZ
AZC005-130500-
/O.EXT.KFGZ.FF.W.0173.000000T0000Z-210813T0500Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Flagstaff AZ
452 PM MST Thu Aug 12 2021

The National Weather Service in Flagstaff has extended the

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

* Until 1000 PM MST.

* At 451 PM MST, Doppler radar indicated that the heavy rainfall has 
  ended. Flooding is still expected as water continues to flow down 
  Kanab Creek over the next several hours. Between 0.5 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...
  Fredonia.

This includes the following highways...
	State Route 389 near mile marker 32.
	U.S. Highway 89A between mile markers 603 and 612.

This includes the following streams and drainages...
  Kanab Creek, Johnson Wash, Johnson Run, Lost Spring Wash, Wildcat 
  Canyon, Jacob Canyon and White Sage Wash.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Stay away or be swept away! The banks of creeks and washes are 
unstable and unsafe during any flooding event.

Remain alert for flooding even in locations not receiving rain. 
Normally dry washes, slot canyons and creeks can become raging 
killer currents in a matter of minutes, even from distant rainfall.

&&

LAT...LON 3700 11234 3693 11238 3688 11247 3685 11259
      3686 11259 3687 11258 3689 11257 3691 11255
      3694 11255 3695 11253 3697 11253 3698 11254
      3700 11254

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

$$

Humphreys

977 
WGUS75 KFGZ 130453
FFSFGZ

Flash Flood Statement
National Weather Service Flagstaff AZ
953 PM MST Thu Aug 12 2021

AZC005-130503-
/O.EXP.KFGZ.FF.W.0173.000000T0000Z-210813T0500Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Coconino AZ-
953 PM MST Thu Aug 12 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 10 PM MST THIS EVENING FOR 
COCONINO COUNTY...

The heavy rain has ended. Flash flooding is no longer expected to 
pose a threat along Kanab Creek. Please heed any road closures and 
don't drive into flowing water on roads.

LAT...LON 3700 11234 3693 11238 3688 11247 3685 11259
      3686 11259 3687 11258 3689 11257 3691 11255
      3694 11255 3695 11253 3697 11253 3698 11254
      3700 11254

$$

McCollum

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 11, 5:35 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Navajo	3 hr
Aug 12, 5:36 AM MST	Flash Flood Warning Considerable damage threat	FGZ	Gila	3 hr
Aug 12, 12:34 PM MST	Special Weather Statement	FGZ	Yavapai	26 min
Aug 12, 12:43 PM MST	Special Weather Statement	FGZ		32 min
Aug 12, 1:08 PM MST	Special Weather Statement	FGZ		22 min
Aug 12, 1:29 PM MST	Special Weather Statement	FGZ		31 min
Aug 12, 3:21 PM MST	Special Weather Statement	FGZ	Yavapai	24 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.