Alert archive / Arizona / Flash Flood Warnings in 2021

Flash Flood Warning 166, NWS Flagstaff, AZ

August 11, 2021Yavapai County, Arizona

NWS Flagstaff, AZ issued this flash flood warning at Aug 11, 2021, 9:30 AM MST for Yavapai 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: Aug 11, 2021, 9:30 AM MST (16:30 UTC)
Expired: Aug 11, 2021, 12:00 PM MST
In force: 3 hr
Issued by: NWS Flagstaff, AZ
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

County Yavapai County, AZ

The radar

The Flagstaff radar (KFSX), 79 km from the middle of the area, began a volume at 16:33 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

Phoenix, AZ (KPSR), launched 12:00Z, 4.5 hours before the alert went out and 73 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: 735 J/kg
Mixed-layer CIN: -36 J/kg
Mixed-layer LCL: 905 m above ground
0-6 km bulk shear: 15 kt
0-1 km storm-relative helicity: 12 m²/s²
0-3 km storm-relative helicity: 53 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

742 
WGUS55 KFGZ 111630
FFWFGZ
AZC025-111900-
/O.NEW.KFGZ.FF.W.0166.210811T1630Z-210811T1900Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Flagstaff AZ
930 AM MST Wed Aug 11 2021

The National Weather Service in Flagstaff has issued a

* Flash Flood Warning for...
  Yavapai County in west central Arizona...

* Until noon MST.

* At 929 AM 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...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...
  Horseshoe Reservoir.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

In hilly or mountainous terrain, there are many low water crossings 
which will become dangerous in heavy rain. Do not attempt to cross 
flooded roads. Find an alternate route.

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 3402 11186 3418 11202 3425 11202 3435 11184
      3428 11175 3420 11187 3400 11164 3400 11168
      3400 11169 3400 11170 3400 11171 3400 11172
      3400 11173 3400 11174 3400 11175 3401 11179
      3401 11181 3401 11184 3401 11185

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

$$

EL

3 follow-up statements

517 
WGUS75 KFGZ 111709
FFSFGZ

Flash Flood Statement
National Weather Service Flagstaff AZ
1009 AM MST Wed Aug 11 2021

AZC025-111900-
/O.CON.KFGZ.FF.W.0166.000000T0000Z-210811T1900Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Yavapai AZ-
1009 AM MST Wed Aug 11 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL NOON MST TODAY FOR 
YAVAPAI COUNTY...

At 1003 AM MST, Doppler radar indicated decreasing rainfall rates 
from thunderstorms across the warned area with the heaviest rainfall 
occurring east of I-17, from Cordes to Bumble Bee, or just southeast 
of Sycamore Creek. Between 1 and 2.5 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...
  Horseshoe Reservoir.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

In hilly or mountainous terrain, there are many low water crossings 
which will become dangerous in heavy rain. Do not attempt to cross 
flooded roads. Find an alternate route.

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 3402 11186 3418 11202 3425 11202 3435 11184
      3428 11175 3420 11187 3400 11164 3400 11168
      3400 11169 3400 11170 3400 11171 3400 11172
      3400 11173 3400 11174 3400 11175 3401 11179
      3401 11181 3401 11184 3401 11185

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

$$

EL

683 
WGUS75 KFGZ 111749
FFSFGZ

Flash Flood Statement
National Weather Service Flagstaff AZ
1049 AM MST Wed Aug 11 2021

AZC025-111900-
/O.CON.KFGZ.FF.W.0166.000000T0000Z-210811T1900Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Yavapai AZ-
1049 AM MST Wed Aug 11 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL NOON MST TODAY FOR 
YAVAPAI COUNTY...

At 1047 AM MST, Doppler radar indicated the heavy rainfall from 
thunderstorms has decreased in intensity across the warned area. 
However, flash flooding is still possible as water drains. Between 1 
and 2.5 inches of rain have fallen.

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...
  Horseshoe Reservoir.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

In hilly or mountainous terrain, there are many low water crossings 
which will become dangerous in heavy rain. Do not attempt to cross 
flooded roads. Find an alternate route.

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 3402 11186 3418 11202 3425 11202 3435 11184
      3428 11175 3420 11187 3400 11164 3400 11168
      3400 11169 3400 11170 3400 11171 3400 11172
      3400 11173 3400 11174 3400 11175 3401 11179
      3401 11181 3401 11184 3401 11185

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

$$

EL

827 
WGUS75 KFGZ 111851
FFSFGZ

Flash Flood Statement
National Weather Service Flagstaff AZ
1151 AM MST Wed Aug 11 2021

AZC025-111901-
/O.EXP.KFGZ.FF.W.0166.000000T0000Z-210811T1900Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Yavapai AZ-
1151 AM MST Wed Aug 11 2021

...FLASH FLOOD WARNING WILL EXPIRE AT NOON MST TODAY FOR YAVAPAI 
COUNTY...

Flood waters have receded and the heavy rain has ended. Flooding is 
no longer expected to pose a threat. Please continue to heed 
remaining road closures.

LAT...LON 3402 11186 3418 11202 3425 11202 3435 11184
      3428 11175 3420 11187 3400 11164 3400 11168
      3400 11169 3400 11170 3400 11171 3400 11172
      3400 11173 3400 11174 3400 11175 3401 11179
      3401 11181 3401 11184 3401 11185

$$

Humphreys

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 11, 1:38 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Yavapai	3 hr
Aug 11, 1:48 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Coconino	3 hr
Aug 11, 2:25 PM MST	Special Weather Statement	FGZ		35 min
Aug 11, 2:49 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Apache	3 hr
Aug 11, 3:11 PM MST	Special Weather Statement	FGZ		34 min
Aug 11, 4:24 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.