Alert archive / Arizona / Flash Flood Warnings in 2021

Flash Flood Warning 78, NWS Flagstaff, AZ

July 21, 2021Coconino County, Arizona

NWS Flagstaff, AZ issued this flash flood warning at Jul 21, 2021, 4:35 PM MST for Coconino County, Arizona. It was in force for 115 min. 1 report came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Jul 21, 2021, 4:35 PM MST (23:35 UTC)
Expired: Jul 21, 2021, 6:30 PM MST
In force: 115 min
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), 153 km from the middle of the area, began a volume at 23:36 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.

What was reported inside it

Time	Report	Where	Remark
Jul 21, 5:00 PM MST	FLASH FLOOD	Supai, AZ	HAVASU CREEK AT SUPAI RIVER GAUGE SHOWED A RISE OF 18 INCHES IN ABOUT AN HOUR. IT TOOK ABOUT 6 HOURS FOR THE RIVER TO RETURN TO ITS ORIGINAL LEVEL.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Flgstf/Belemont, AZ (KFGZ), launched 12:00Z, 11.6 hours before the alert went out and 138 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: 77 J/kg
Mixed-layer CIN: -129 J/kg
Mixed-layer LCL: 1785 m above ground
0-6 km bulk shear: 8 kt
0-1 km storm-relative helicity: 20 m²/s²
0-3 km storm-relative helicity: -11 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

904 
WGUS55 KFGZ 212335
FFWFGZ
AZC005-220030-
/O.NEW.KFGZ.FF.W.0078.210721T2335Z-210722T0030Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Flagstaff AZ
435 PM MST Wed Jul 21 2021

The National Weather Service in Flagstaff has issued a

* Flash Flood Warning for...
  The Havasu Creek basin in...
  Coconino County in north central Arizona...

* Until 530 PM MST.

* At 434 PM MST, Doppler radar indicated thunderstorms producing 
  heavy rain over the Havasu Creek basin. Between 0.5 and 1 inch of 
  rain has fallen. Flash flooding is ongoing or expected to begin 
  shortly.

  HAZARD...Thunderstorms producing flash flooding in and around
           the Havasu Creek basin.

  SOURCE...Radar.

  IMPACT...Life threatening flash flooding of areas in and around
           the Havasu Creek basin.

* Some locations that will experience flash flooding include...
  Grand Canyon National Park, Hualapai Hilltop, Supai and Havasupai 
  Reservation.

This includes the following swimming holes...
	All swimming holes on Havasu Creek near Supai.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Campers and hikers should hustle to higher ground immediately! Stay 
away from creeks and washes!

Foot bridges will be washed out in Supai Campground. Some campsites 
will be flooded. Campers may be stranded in portions of the 
campground.

&&

LAT...LON 3629 11275 3630 11277 3631 11276 3632 11276
      3631 11273 3627 11269 3611 11258 3610 11263
      3620 11269 3615 11271 3611 11271 3613 11274
      3624 11272 3627 11273 3619 11274 3617 11276
      3624 11277

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

$$

McCollum

2 follow-up statements

531 
WGUS55 KFGZ 220027
FFWFGZ
AZC005-220130-
/O.EXT.KFGZ.FF.W.0078.000000T0000Z-210722T0130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Flagstaff AZ
527 PM MST Wed Jul 21 2021

The National Weather Service in Flagstaff has extended the

* Flash Flood Warning for...
  The Havasu Creek basin in...
  Coconino County in north central Arizona...

* Until 630 PM MST.

* At 524 PM MST, Doppler radar indicated thunderstorms that produced 
  heavy rain over the Havasu Creek basin have dissipated. However, 
  between 0.5 and 1 inches of rain has fallen. The potential for 
  flash flooding continues.

  HAZARD...Thunderstorms producing flash flooding in and around
           the Havasu Creek basin.

  SOURCE...Radar.

  IMPACT...Flash flooding of areas in and around the Havasu Creek
           basin.

* Some locations that will experience flash flooding include...
  Hualapai Hilltop, Supai and Havasupai Reservation.

This includes the following swimming holes...
	All swimming holes on Havasu Creek near Supai.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Campers and hikers should hustle to higher ground immediately! Stay 
away from creeks and washes!

Foot bridges will be washed out in Supai Campground. Some campsites 
will be flooded. Campers may be stranded in portions of the 
campground.

&&

LAT...LON 3629 11275 3630 11277 3631 11276 3632 11276
      3631 11273 3627 11269 3611 11258 3610 11263
      3620 11269 3615 11271 3611 11271 3613 11274
      3624 11272 3627 11273 3619 11274 3617 11276
      3624 11277

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

$$

McCollum

958 
WGUS75 KFGZ 220126
FFSFGZ

Flash Flood Statement
National Weather Service Flagstaff AZ
626 PM MST Wed Jul 21 2021

AZC005-220136-
/O.EXP.KFGZ.FF.W.0078.000000T0000Z-210722T0130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Coconino AZ-
626 PM MST Wed Jul 21 2021

...FLASH FLOOD WARNING FOR THE HAVASU CREEK BASIN WILL EXPIRE AT 630 
PM MST THIS EVENING FOR COCONINO COUNTY...

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

LAT...LON 3629 11275 3630 11277 3631 11276 3632 11276
      3631 11273 3627 11269 3611 11258 3610 11263
      3620 11269 3615 11271 3611 11271 3613 11274
      3624 11272 3627 11273 3619 11274 3617 11276
      3624 11277

$$

McCollum

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 20, 6:16 PM MST	Special Weather Statement	FGZ		29 min
Jul 20, 7:32 PM MST	Severe Thunderstorm Warning	FGZ	Navajo	28 min
Jul 20, 7:55 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Navajo	2 hr
Jul 20, 8:33 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Navajo	117 min
Jul 21, 12:17 AM MST	Flash Flood Warning Considerable damage threat	FGZ	Gila	118 min
Jul 21, 2:38 AM MST	Flash Flood Watch	FGZ	Apache, Coconino, Gila, Navajo, Yavapai	5 days
Jul 21, 10:19 AM MST	Special Weather Statement	FGZ	Yavapai	26 min
Jul 21, 10:48 AM MST	Flash Flood Warning Considerable damage threat	FGZ	Yavapai	2 hr
Jul 21, 12:03 PM MST	Special Weather Statement	FGZ	Yavapai	42 min
Jul 21, 12:13 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Yavapai	56 min
Jul 21, 12:20 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Yavapai	114 min
Jul 21, 12:35 PM MST	Special Weather Statement	FGZ		40 min
Jul 21, 12:47 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Coconino	118 min
Jul 21, 12:54 PM MST	Special Weather Statement	FGZ		36 min
Jul 21, 1:06 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Coconino	92 min
Jul 21, 1:24 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Coconino	110 min
Jul 21, 1:27 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Yavapai	74 min
Jul 21, 1:57 PM MST	Special Weather Statement	FGZ	Yavapai	48 min
Jul 21, 2:01 PM MST	Areal Flood Advisory	FGZ	Yavapai	119 min
Jul 21, 2:05 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Coconino	2 hr
Jul 21, 2:22 PM MST	Areal Flood Advisory	FGZ	Coconino	3 hr
Jul 21, 2:30 PM MST	Special Weather Statement	FGZ		45 min
Jul 21, 2:36 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Yavapai	54 min
Jul 21, 2:53 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Coconino	82 min
Jul 21, 2:57 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Yavapai	60 min
Jul 21, 2:59 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Yavapai	60 min
Jul 21, 3:21 PM MST	Severe Thunderstorm Warning	FGZ	Coconino	26 min
Jul 21, 3:34 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Coconino	98 min
Jul 21, 3:49 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Yavapai	3 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.