Alert archive / Arizona / Flash Flood Warnings in 2021

Flash Flood Warning 216, NWS Flagstaff, AZ

August 18, 2021Coconino County, Arizona

NWS Flagstaff, AZ issued this flash flood warning at Aug 18, 2021, 11:56 PM MST for Coconino County, Arizona. It was in force for 8 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 18, 2021, 11:56 PM MST (06:56 UTC)
Expired: Aug 19, 2021, 8:00 AM MST
In force: 8 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), 125 km from the middle of the area, began a volume at 06:59 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, 6.9 hours before the alert went out and 190 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: 605 J/kg
Mixed-layer CIN: -17 J/kg
Mixed-layer LCL: 745 m above ground
0-6 km bulk shear: 19 kt
0-1 km storm-relative helicity: 109 m²/s²
0-3 km storm-relative helicity: 108 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 1.8

Open this sounding in Storm Lab

The text

As transmitted.

164 
WGUS55 KFGZ 190656
FFWFGZ
AZC005-191500-
/O.NEW.KFGZ.FF.W.0216.210819T0656Z-210819T1500Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Flagstaff AZ
1156 PM MST Wed Aug 18 2021

The National Weather Service in Flagstaff has issued a

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

* Until 800 AM MST Thursday.

* At 1153 PM MST, gauge reports indicated high water flowing down 
  the Paria River due to heavy rainfall upstream. Flash flooding is 
  already occurring.

  HAZARD...Life-threatening flash flooding. Thunderstorms
           upstream producing flash flooding in and around the
           Paria River.

  SOURCE...Gauges reported.

  IMPACT...Life threatening flash flooding of areas in and around
           the Paria River.

* Some locations that will experience flash flooding include...
  Lees Ferry, Glen Canyon National Recreation Area, Grand Canyon 
  National Park and Navajo Reservation.

This includes the following slot canyons...
	Paria River upstream of Lees Ferry.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Get out of the Paria River slot canyon! Flood waters will flow down 
the Paria River, reaching the confluence with the Colorado River at 
Lees Ferry between 7 AM MST and 8 AM MST.

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

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

&&

LAT...LON 3694 11166 3686 11157 3685 11159 3690 11166
      3693 11172 3696 11180 3697 11186 3700 11188
      3700 11170

FLASH FLOOD...GAUGE INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

Humphreys

1 follow-up statement

378 
WGUS75 KFGZ 191455
FFSFGZ

Flash Flood Statement
National Weather Service Flagstaff AZ
755 AM MST Thu Aug 19 2021

AZC005-191505-
/O.EXP.KFGZ.FF.W.0216.000000T0000Z-210819T1500Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Coconino AZ-
755 AM MST Thu Aug 19 2021

...FLASH FLOOD WARNING FOR THE PARIA RIVER WILL EXPIRE AT 8 AM MST 
THIS MORNING FOR COCONINO COUNTY...

The river gauge at Lees Ferry has peaked at 8.45 feet earlier this 
morning and the flood waters have begun to recede. Flood waters and 
flow will continue to be elevated throughout the remaining of this 
morning., however flooding is no longer expected to pose a threat. 
Please continue to heed remaining road closures and stay away from 
the banks of the Paria River through this morning.

LAT...LON 3694 11166 3686 11157 3685 11159 3690 11166
      3693 11172 3696 11180 3697 11186 3700 11188
      3700 11170

$$

EL

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 18, 5:13 PM MST	Flash Flood Warning	FGZ	Yavapai	3 hr
Aug 18, 5:17 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Coconino, Yavapai	4 hr
Aug 18, 5:31 PM MST	Special Weather Statement	FGZ	Yavapai	29 min
Aug 18, 5:43 PM MST	Severe Thunderstorm Warning	FGZ	Coconino	23 min
Aug 18, 7:59 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Gila	4 hr
Aug 18, 8:08 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Yavapai	6 hr
Aug 18, 10:41 PM MST	Areal Flood Warning	FGZ	Gila, Yavapai	10 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.