Alert archive / Arizona / Flash Flood Warnings in 2021

Flash Flood Warning 60, NWS Flagstaff, AZ

July 20, 2021Coconino County, Arizona

NWS Flagstaff, AZ issued this flash flood warning at Jul 20, 2021, 3:45 PM MST for Coconino 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: Jul 20, 2021, 3:45 PM MST (22:45 UTC)
Expired: Jul 20, 2021, 6:45 PM MST
In force: 3 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), 148 km from the middle of the area, began a volume at 22:48 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, 10.8 hours before the alert went out and 140 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: 396 J/kg
Mixed-layer CIN: -58 J/kg
Mixed-layer LCL: 1392 m above ground
0-6 km bulk shear: 14 kt
0-1 km storm-relative helicity: 16 m²/s²
0-3 km storm-relative helicity: 5 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

808 
WGUS55 KFGZ 202245
FFWFGZ
AZC005-210145-
/O.NEW.KFGZ.FF.W.0060.210720T2245Z-210721T0145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Flagstaff AZ
345 PM MST Tue Jul 20 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 343 PM MST, Doppler radar indicated thunderstorms producing 
  heavy rain in portions of the Grand Canyon including the North 
  Canyon and South Canyon drainages, as well as the Tatahatso Wash. 
  Between 1 and 2 inches of rain have fallen. Additional rainfall 
  amounts of 0.5 to 0.75 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...
  Grand Canyon National Park and Navajo Reservation.

This includes the following highways...
	State Route 67 near mile marker 607.

This includes the following streams and drainages...
  Tatahatso Wash, South Canyon, North Canyon Wash, Colorado River, 
  House Rock Wash, Pleasant Valley Outlet and Tatahoysa Wash.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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.

Get out of washes and creeks if you are camping or hiking! Flooding 
is occurring or imminent and will inundate area drainages.

&&

LAT...LON 3648 11206 3656 11195 3662 11184 3659 11182
      3650 11185 3642 11170 3634 11199 3639 11214

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

$$

JJ

2 follow-up statements

355 
WGUS75 KFGZ 210028
FFSFGZ

Flash Flood Statement
National Weather Service Flagstaff AZ
528 PM MST Tue Jul 20 2021

AZC005-210145-
/O.CON.KFGZ.FF.W.0060.000000T0000Z-210721T0145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Coconino AZ-
528 PM MST Tue Jul 20 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 645 PM MST THIS 
EVENING FOR COCONINO COUNTY...

At 526 PM MST, Doppler radar indicated thunderstorms producing heavy 
rain have ended across portions of the Grand Canyon including the 
North Canyon and South Canyon drainages, as well as the Tatahatso 
Wash. Light to occasionally moderate rain will gradually diminish 
over the next couple hours. Between 1.25 and 2.25 inches of rain 
have fallen. Additional rainfall amounts up to 0.25 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...
  Grand Canyon National Park and Navajo Reservation.

This includes the following highways...
	State Route 67 between mile markers 606 and 607.

This includes the following streams and drainages...
  Tatahatso Wash, South Canyon, North Canyon Wash, Colorado River, 
  House Rock Wash, Pleasant Valley Outlet and Tatahoysa Wash.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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.

Get out of washes and creeks if you are camping or hiking! Flooding 
is occurring or imminent and will inundate area drainages.

&&

LAT...LON 3648 11206 3656 11195 3662 11184 3659 11182
      3650 11185 3642 11170 3634 11199 3639 11214

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

$$

TPS

993 
WGUS75 KFGZ 210140
FFSFGZ

Flash Flood Statement
National Weather Service Flagstaff AZ
640 PM MST Tue Jul 20 2021

AZC005-210150-
/O.EXP.KFGZ.FF.W.0060.000000T0000Z-210721T0145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Coconino AZ-
640 PM MST Tue Jul 20 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 645 PM MST THIS EVENING FOR 
COCONINO COUNTY...

The heavy rain threat has ended across portions of the Grand Canyon. 
Lingering light rain will diminish in the next couple hours. 
Flooding is no longer expected to pose a threat. Please continue to 
heed remaining road closures.

LAT...LON 3648 11206 3656 11195 3662 11184 3659 11182
      3650 11185 3642 11170 3634 11199 3639 11214

$$

TPS

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 19, 6:31 PM MST	Severe Thunderstorm Warning	FGZ	Gila	29 min
Jul 20, 11:44 AM MST	Severe Thunderstorm Warning	FGZ	Yavapai	35 min
Jul 20, 11:53 AM MST	Flash Flood Warning Considerable damage threat	FGZ	Yavapai	3 hr
Jul 20, 1:14 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Yavapai	3 hr
Jul 20, 1:23 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Coconino	3 hr
Jul 20, 1:39 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Yavapai	3 hr
Jul 20, 4:57 PM MST	Special Weather Statement	FGZ		48 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.