Alert archive / Arizona / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 145, NWS Flagstaff, AZ

August 16, 2021Apache County, Arizona

NWS Flagstaff, AZ issued this severe thunderstorm warning at Aug 16, 2021, 4:25 PM MST for Apache County, Arizona. It was in force for 35 min. 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 16, 2021, 4:25 PM MST (23:25 UTC)
Expired: Aug 16, 2021, 5:00 PM MST
In force: 35 min
Issued by: NWS Flagstaff, AZ
Area: Storm-based polygon
Hail: 1.0 in
Wind: 60.0 mph

County Apache County, AZ

The radar

The Flagstaff radar (KFSX), 142 km from the middle of the area, began a volume at 23:26 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.

Did it verify

Not verified. The Iowa Environmental Mesonet's Cow found no qualifying storm report inside this severe thunderstorm warning while it was in force. That is not proof nothing happened: reports are thin where few people live.

Cow counts a report within 15 km of the polygon while the warning was in force: a tornado for a tornado warning; hail of 1 inch or more, a gust of 58 mph or more or wind damage for a severe thunderstorm warning; a flash flood report for a flash flood warning.

The nearest sounding before it

Flgstf/Belemont, AZ (KFGZ), launched 12:00Z, 11.4 hours before the alert went out and 214 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: 428 J/kg
Mixed-layer CIN: -132 J/kg
Mixed-layer LCL: 1562 m above ground
0-6 km bulk shear: 20 kt
0-1 km storm-relative helicity: 51 m²/s²
0-3 km storm-relative helicity: 67 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

205 
WUUS55 KFGZ 162325
SVRFGZ
AZC001-170000-
/O.NEW.KFGZ.SV.W.0145.210816T2325Z-210817T0000Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Flagstaff AZ
425 PM MST Mon Aug 16 2021

The National Weather Service in Flagstaff has issued a

* Severe Thunderstorm Warning for...
  Apache County in northeastern Arizona...

* Until 500 PM MST.

* At 424 PM MST, a severe thunderstorm was located 7 miles south of
  Concho moving southeast at 15 mph.

  HAZARD...60 mph wind gusts and quarter size hail.

  SOURCE...Radar indicated.

  IMPACT...Hail damage to vehicles is expected. Expect wind damage 
           to roofs, siding, and trees.

* Locations impacted include...
  Concho and Little Ortega Lake. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 3449 10977 3456 10957 3440 10944 3434 10971
TIME...MOT...LOC 2324Z 334DEG 14KT 3436 10958 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

ET

1 follow-up statement

509 
WWUS55 KFGZ 162351
SVSFGZ

Severe Weather Statement
National Weather Service Flagstaff AZ
451 PM MST Mon Aug 16 2021

AZC001-170001-
/O.EXP.KFGZ.SV.W.0145.000000T0000Z-210817T0000Z/
Apache-
451 PM MST Mon Aug 16 2021

...THE SEVERE THUNDERSTORM WARNING FOR APACHE COUNTY WILL EXPIRE AT
500 PM MST...
                
The storm which prompted the warning has weakened below severe
limits, and no longer poses an immediate threat to life or property.
Therefore, the warning will be allowed to expire.  However heavy rain
is still possible with this thunderstorm.

LAT...LON 3449 10977 3456 10957 3440 10944 3434 10971
TIME...MOT...LOC 2351Z 334DEG 14KT 3428 10953 

$$

ET

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Flagstaff, AZ wrote its last area forecast discussion before this severe thunderstorm warning went out at Aug 16, 2:58 PM MST, 1 hour 27 minutes earlier.

Area forecast discussion, Aug 16, 2:58 PM MST, 1 hour 27 minutes before

Area Forecast Discussion
National Weather Service Flagstaff AZ
258 PM MST Mon Aug 16 2021

.SYNOPSIS...Scattered thunderstorms will continue this evening,
with storms most numerous along and south of the Mogollon Rim
where a few strong to severe storms are possible. Expect
widespread showers and storms again on Tuesday and Wednesday,
before a drying trend arrives toward the end of the week.

&&

.DISCUSSION...Very strong and severe thunderstorms currently
developing over the central and eastern Rim, with a broader area
of somewhat weaker storms over the NE. Current mesoscale analyses
show strong instability along and southwest of the Rim, with the
greatest instability still analyzed over Yavapai County. We expect
thunderstorms to continue develop across the area this afternoon
and evening, with the strongest storms evolving toward the south,
possibly growing upscale into a an MCS as it organizes along
outflow boundaries. Greatest threat this afternoon and evening
will be damaging winds and large hail. Training (redeveloping)
storms may create local flash flood threats. Recent high-
resolution models support this development.

On Tuesday, the instability will be pulled farther north ahead of
a developing trough to the west. Scattered to numerous
thunderstorms are expected once again, but the nature of the
convection will be different - that is - storms will be most
numerous along and north of the Rim on Tuesday, with slowly
eastward-moving storms. The slow motion of the storms may
engender a greater flash flood threat, and greater shear could
promote organized severe thunderstorms.

The strong trough moving across the N Rockies will push the
greatest thunderstorm threat on Wednesday into NE Arizona. Cooler
temperatures and drier weather is expected later in the week as
the trough sweeps the moisture out of the area, and brings a break
to this current round of monsoon activity. Current ensemble
solutions indicate that Arizona should be generally dry through
the weekend.

&&

.AVIATION...For the 00Z package...Scattered to numerous
thunderstorms are expected this afternoon and evening, with
coverage increasing south of the Mogollon Rim after 01Z. Localized
IFR conditions expected in and near strongest storms. Storms will
decrease from north to south after 04Z, and develop again after
18Z on Tue. Aviation discussion not updated for TAF amendments.

&&

.DISCUSSION...Scattered to numerous showers and thunderstorms are
expected through Wednesday. Large hail, localized flash flooding
and very gusty outflow winds are the main hazards. Winds outside
storms will be light, with temperatures cooling Tuesday and
Wednesday.

Thursday through Saturday...Drier weather is expected on Thursday
through Saturday, with below normal temperatures expected.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...NONE.

&&

PUBLIC...BAK
AVIATION...BAK
FIRE WEATHER...BAK

For Northern Arizona weather information visit
weather.gov/flagstaff

In the hours before

Special weather statement, Aug 16, 11:55 AM MST, 4 hours 30 minutes before

Special Weather Statement
National Weather Service Flagstaff AZ
1255 PM MDT Mon Aug 16 2021

AZZ011-161930-
Chuska Mountains and Defiance Plateau-
1255 PM MDT Mon Aug 16 2021

...Two strong thunderstorms will impact portions of Apache County
through 130 PM MDT...

At 1253 PM MDT, Doppler radar was tracking two strong thunderstorms
near Lupton and Window Rock, or 23 miles west of Gallup, moving
southeast at 5 mph.

HAZARD...Wind gusts up to 50 mph and penny size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Lupton, Oak Springs Valley, Window Rock and St. Michaels.

This includes the following highways...
 Interstate 40 between mile markers 350 and 359.
 State Route 264 between mile markers 462 and 474.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 3525 10905 3519 10917 3580 10932 3582 10911
      3548 10904
TIME...MOT...LOC 1853Z 329DEG 6KT 3539 10913

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...50 MPH

DB

Local storm report, Aug 16, 12:17 PM MST, 4 hours 8 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
1217 PM MST MON AUG 16 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1211 PM     HAIL             HEBER-OVERGAARD         34.42N 110.57W
08/16/2021  E0.50 INCH       NAVAJO             AZ   PUBLIC

&&

Local storm report, Aug 16, 2:00 PM MST, 2 hours 25 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
200 PM MST MON AUG 16 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0152 PM     HAIL             2 WSW HEBER-OVERGAARD   34.40N 110.59W
08/16/2021  E1.00 INCH       NAVAJO             AZ   TRAINED SPOTTER

&&

Local storm report, Aug 16, 2:49 PM MST, 1 hour 36 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
249 PM MST MON AUG 16 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0248 PM     HAIL             8 E MOUNTAINAIRE        35.08N 111.52W
08/16/2021  E1.00 INCH       COCONINO           AZ   TRAINED SPOTTER

&&

MD

Local storm report, Aug 16, 3:53 PM MST, 32 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
353 PM MST MON AUG 16 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0350 PM     FLOOD            1 W HEBER-OVERGAARD     34.42N 110.59W
08/16/2021                   NAVAJO             AZ   PUBLIC

            NUMEROUS LOW WATER CROSSINGS FLOODED AND
            ROADS CLOSURES ACROSS WESTERN PORTIONS OF
            HEBER.

&&

DM

Local storm report, Aug 16, 4:17 PM MST, 8 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
417 PM MST MON AUG 16 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0301 PM     HAIL             MOUNTAINAIRE            35.08N 111.66W
08/16/2021  E1.50 INCH       COCONINO           AZ   PUBLIC

&&

DM

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 15, 5:29 PM MST	Severe Thunderstorm Warning	FGZ	Coconino, Navajo	31 min
Aug 15, 5:47 PM MST	Severe Thunderstorm Warning	FGZ	Apache	18 min
Aug 15, 6:17 PM MST	Severe Thunderstorm Warning	FGZ	Apache	12 min
Aug 15, 6:54 PM MST	Severe Thunderstorm Warning	FGZ	Coconino	36 min
Aug 15, 7:46 PM MST	Severe Thunderstorm Warning	FGZ	Coconino	29 min
Aug 15, 7:53 PM MST	Severe Thunderstorm Warning	FGZ	Navajo	26 min
Aug 15, 8:17 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Coconino	3 hr
Aug 15, 8:29 PM MST	Severe Thunderstorm Warning	FGZ	Gila	31 min
Aug 15, 10:27 PM MST	Severe Thunderstorm Warning	FGZ	Yavapai	33 min
Aug 15, 11:01 PM MST	Severe Thunderstorm Warning	FGZ	Yavapai	29 min
Aug 15, 11:06 PM MST	Severe Thunderstorm Warning	FGZ	Yavapai	24 min
Aug 15, 11:27 PM MST	Severe Thunderstorm Warning	FGZ	Yavapai	21 min
Aug 15, 11:50 PM MST	Special Weather Statement	FGZ	Yavapai	25 min
Aug 16, 12:08 AM MST	Severe Thunderstorm Warning	FGZ	Yavapai	37 min
Aug 16, 12:40 AM MST	Severe Thunderstorm Warning	FGZ	Yavapai	35 min
Aug 16, 1:00 AM MST	Severe Thunderstorm Warning	FGZ	Yavapai	45 min
Aug 16, 11:55 AM MST	Special Weather Statement	FGZ	Apache	35 min
Aug 16, 1:30 PM MST	Severe Thunderstorm Warning	FGZ	Coconino	45 min
Aug 16, 1:38 PM MST	Severe Thunderstorm Warning	FGZ	Navajo	52 min
Aug 16, 1:47 PM MST	Severe Thunderstorm Warning	FGZ	Coconino	43 min
Aug 16, 2:09 PM MST	Flash Flood Warning	FGZ	Navajo	3 hr
Aug 16, 2:16 PM MST	Flash Flood Warning	FGZ	Coconino	3 hr
Aug 16, 2:25 PM MST	Severe Thunderstorm Warning	FGZ	Coconino	50 min
Aug 16, 2:27 PM MST	Severe Thunderstorm Warning Considerable damage threat	FGZ	Coconino, Navajo	33 min
Aug 16, 2:30 PM MST	Severe Thunderstorm Warning	FGZ	Apache, Navajo	45 min
Aug 16, 2:38 PM MST	Severe Thunderstorm Warning Considerable damage threat	FGZ	Coconino, Gila, Navajo	37 min
Aug 16, 2:41 PM MST	Severe Thunderstorm Warning Considerable damage threat	FGZ	Coconino, Yavapai	34 min
Aug 16, 3:06 PM MST	Severe Thunderstorm Warning	FGZ	Apache, Navajo	22 min
Aug 16, 3:10 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Apache	3 hr
Aug 16, 3:39 PM MST	Severe Thunderstorm Warning	FGZ	Coconino, Gila	36 min
Aug 16, 3:57 PM MST	Severe Thunderstorm Warning	FGZ	Apache	33 min
Aug 16, 4:34 PM MST	Severe Thunderstorm Warning	FGZ	Gila	26 min
Aug 16, 4:42 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Apache	4 hr

Nearby

Severe Thunderstorm Warnings in Arizona, 2021 Every severe thunderstorm 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.