Alert archive / Arizona / Flash Flood Warnings in 2021

Flash Flood Warning 234, NWS Flagstaff, AZ

September 29, 2021Coconino County, Arizona

NWS Flagstaff, AZ issued this flash flood warning at Sep 29, 2021, 6:58 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: Sep 29, 2021, 6:58 PM MST (01:58 UTC)
Expired: Sep 29, 2021, 10:00 PM MST
In force: 3 hr
Issued by: NWS Flagstaff, AZ
Area: Storm-based polygon
Flood severity: None

County Coconino County, AZ

The radar

The Flagstaff radar (KFSX), 70 km from the middle of the area, began a volume at 01:58 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, 2.0 hours before the alert went out and 26 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: 196 J/kg
Mixed-layer CIN: -2 J/kg
Mixed-layer LCL: 1391 m above ground
0-6 km bulk shear: 15 kt
0-1 km storm-relative helicity: 18 m²/s²
0-3 km storm-relative helicity: 37 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

435 
WGUS55 KFGZ 300158
FFWFGZ
AZC005-300500-
/O.NEW.KFGZ.FF.W.0234.210930T0158Z-210930T0500Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Flagstaff AZ
658 PM MST Wed Sep 29 2021

The National Weather Service in Flagstaff has issued a

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

* Until 1000 PM MST.

* At 653 PM MST, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1 and 2 inches of rain 
  have fallen. Additional rainfall amounts of 0.5 to 1 inch are 
  possible in the warned area. Flash flooding is ongoing or expected 
  to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar.

  IMPACT...Flash flooding of low-water crossings, creeks,
           normally dry washes and roads.

* Some locations that will experience flash flooding include...
  West Fork Of Oak Creek.

This includes the following creeks, washes and rivers...
  Dry Creek and West Fork Oak Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

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

With heavy rain, rock falls are common in this area. Watch out for 
falling rocks near cliffs and rocks on roadways.

Report any flooding to local law enforcement and the NWS Flagstaff 
when you can do so safely.

&&

LAT...LON 3499 11175 3500 11177 3498 11180 3499 11181
      3502 11178 3501 11174

FLASH FLOOD...RADAR INDICATED

$$

DB

2 follow-up statements

510 
WGUS75 KFGZ 300351
FFSFGZ

Flash Flood Statement
National Weather Service Flagstaff AZ
851 PM MST Wed Sep 29 2021

AZC005-300500-
/O.CON.KFGZ.FF.W.0234.000000T0000Z-210930T0500Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Coconino AZ-
851 PM MST Wed Sep 29 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 10 PM MST THIS 
EVENING FOR COCONINO COUNTY...

At 846 PM MST, Doppler radar indicated thunderstorms producing heavy 
rain across the warned area has ended for the most part. Between 2 
and 3 inches of rain have fallen. Flash flooding is ongoing or 
expected to begin shortly. Though the rain has stopped, the basin 
above the West Fork of Oak Creek will continue to drain for the next 
hour or more.

HAZARD...Flash flooding caused by thunderstorms.

SOURCE...Radar.

IMPACT...Flash flooding of low-water crossings, creeks, normally
         dry washes and roads.

Some locations that will experience flash flooding include...
  West Fork Of Oak Creek.

This includes the following creeks, washes and rivers...
  Dry Creek and West Fork Oak Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

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

With heavy rain, rock falls are common in this area. Watch out for 
falling rocks near cliffs and rocks on roadways.

Report any flooding to local law enforcement and the NWS Flagstaff 
when you can do so safely.

&&

LAT...LON 3499 11175 3500 11177 3498 11180 3499 11181
      3502 11178 3501 11174

FLASH FLOOD...RADAR INDICATED

$$

DB

410 
WGUS75 KFGZ 300457
FFSFGZ

Flash Flood Statement
National Weather Service Flagstaff AZ
957 PM MST Wed Sep 29 2021

AZC005-300507-
/O.EXP.KFGZ.FF.W.0234.000000T0000Z-210930T0500Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Coconino AZ-
957 PM MST Wed Sep 29 2021

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

The heavy rain has ended. Flooding is no longer expected to pose a 
threat, but increased flow may continue in the area overnight as the 
basin above the West Fork of Oak Creek drains into the area. Please 
continue to exercise caution in the area and heed any remaining road 
closures.

LAT...LON 3499 11175 3500 11177 3498 11180 3499 11181
      3502 11178 3501 11174

$$

DB

The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 29, 5:19 PM MST	Special Weather Statement	FGZ	Yavapai	26 min
Sep 29, 5:39 PM MST	Special Weather Statement	FGZ		51 min
Sep 29, 5:44 PM MST	Special Weather Statement	FGZ		46 min
Sep 29, 7:48 PM MST	Special Weather Statement	FGZ		27 min
Sep 29, 8:41 PM MST	Special Weather Statement	FGZ		34 min
Sep 30, 12:02 AM MST	Severe Thunderstorm Warning	FGZ	Gila, Navajo	28 min
Sep 30, 1:53 PM MST	Special Weather Statement	FGZ		37 min
Sep 30, 2:01 PM MST	Severe Thunderstorm Warning	FGZ	Coconino, Yavapai	29 min
Sep 30, 3:23 PM MST	Special Weather Statement	FGZ		22 min
Sep 30, 4:01 PM MST	Special Weather Statement	FGZ		29 min
Sep 30, 4:35 PM MST	Special Weather Statement	FGZ		25 min
Sep 30, 4:52 PM MST	Special Weather Statement	FGZ		23 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.