Alert archive / Arizona / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 25, NWS Flagstaff, AZ

July 10, 20214 counties in Arizona

NWS Flagstaff, AZ issued this severe thunderstorm warning at Jul 10, 2021, 5:16 PM MST for 4 counties in Arizona. It was in force for 44 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 10, 2021, 5:16 PM MST (00:16 UTC)
Expired: Jul 10, 2021, 6:00 PM MST
In force: 44 min
Issued by: NWS Flagstaff, AZ
Area: Storm-based polygon
Hail: 1.25 in
Wind: 70.0 mph

Counties Apache County, AZ, Coconino County, AZ, Gila County, AZ, Navajo County, AZ

The radar

The Flagstaff radar (KFSX), 126 km from the middle of the area, began a volume at 00:19 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 10, 5:20 PM MST	HAIL 1	3 Se Forest Lakes, AZ	HAIL ESTIMATED FROM SOCIAL MEDIA.

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

Did it verify

Verified. The Iowa Environmental Mesonet's Cow matched one storm report to this severe thunderstorm warning; the first came 4 minutes after it went out.

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 watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
Jul 10, 4:52 PM MST	Severe Thunderstorm Watch	SPC	7 hr

The nearest sounding before it

Phoenix, AZ (KPSR), launched 00:00Z, 0.3 hours before the alert went out and 167 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: 965 J/kg
Mixed-layer CIN: -311 J/kg
Mixed-layer LCL: 3378 m above ground
0-6 km bulk shear: 32 kt
0-1 km storm-relative helicity: 2 m²/s²
0-3 km storm-relative helicity: 116 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.0

Open this sounding in Storm Lab

The text

As transmitted.

575 
WUUS55 KFGZ 110016
SVRFGZ
AZC001-005-007-017-110100-
/O.NEW.KFGZ.SV.W.0025.210711T0016Z-210711T0100Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Flagstaff AZ
516 PM MST Sat Jul 10 2021

The National Weather Service in Flagstaff has issued a

* Severe Thunderstorm Warning for...
  Gila County in east central Arizona...
  Apache County in northeastern Arizona...
  Navajo County in north central Arizona...
  Coconino County in north central Arizona...

* Until 600 PM MST.

* At 515 PM MST, severe thunderstorms were located along a line
  extending from 8 miles southeast of Forest Lakes to near North
  Fork, moving southwest at 15 mph.

  HAZARD...70 mph wind gusts and half dollar size hail.

  SOURCE...Radar indicated.

  IMPACT...Hail damage to vehicles is expected. Expect considerable 
           tree damage. Wind damage is also likely to mobile homes, 
           roofs, and outbuildings.

* Locations impacted include...
  Whiteriver, Turkey Creek, Young, Carrizo, Seven Mile, Rainbow City,
  Cedar Creek, Fort Apache Reservation, Fort Apache, White Mountain
  Apache Reservation, East Fork, Canyon Day, Airplane Flat
  Campground, Cibecue, Gentry Campground, Canyon Creek Fish Hatchery
  and Black Canyon Rim Campground.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Torrential rainfall is occurring with these storms, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.

&&

LAT...LON 3358 11000 3361 11000 3361 11005 3383 11032
      3383 11052 3406 11099 3434 11078 3382 10961
      3357 10988
TIME...MOT...LOC 0015Z 050DEG 27KT 3425 11070 3397 11003 

HAIL...1.25IN
WIND...70MPH
 
$$

RR

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 Jul 10, 3:46 PM MST, 1 hour 30 minutes earlier.

Area forecast discussion, Jul 10, 3:46 PM MST, 1 hour 30 minutes before

Area Forecast Discussion
National Weather Service Flagstaff AZ
345 PM MST Sat Jul 10 202

.SYNOPSIS...Hot weather continues this weekend, with chances of
afternoon and evening showers and thunderstorms, primarily south of
the I-40 corridor. More significant moisture looks to return next
week, with greater chances for showers and thunderstorms across
much of northern and central Arizona.

&&

.DISCUSSION...Convection has fired off pretty much as expected, with
the exception of a fairly active area that formed in central Navajo
and Apache counties, that is now approaching the I-40 corridor.
Activity should diminish and head into the lower deserts this
evening, with clearing skies from the north.

Somewhat quieter on Sunday as we lose some boundary layer moisture
and remain warm aloft. This will be short-lived, as the doors are
fully open to the monsoon next week. Expect active weather next week
as we ramp into moderate/high monsoon levels. Flash flooding and
severe hail will become more common each day.

Heat peaks today, still around tomorrow, then next week will cool to
more seasonable levels.

&&

.AVIATION...For the 00Z package...Expect mainly VFR conditions
for the 24 hour TAF forecast period. Sct SHRA/TSRA and ISOLD +TSRA
producing brief MVFR along and south of the I-40 corridor through
03Z Sunday. Similar conditions redevelop again AFT 18Z-19Z Sunday.
Sfc winds 5-15kts outside of storms. Aviation discussion not updated
for TAF amendments.

&&

.FIRE WEATHER...Scattered showers and thunderstorms are expected
again on Sunday, mainly south of the I-40 corridor. Activity will
increase Monday, with lowering temperatures.

Tuesday through Thursday...Expect an active pattern, with scattered
to numerous showers and thunderstorms each day. As a result, expect
cooler temperatures and generally light winds.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...

Excessive Heat Warning until 8 PM MST Saturday for AZZ037.

Excessive Heat Warning until 8 PM MST Sunday for AZZ005-006.

&&

PUBLIC...Peterson
AVIATION...Peterson
FIRE WEATHER...Peterson

For Northern Arizona weather information visit
weather.gov/flagstaff

In the hours before

Special weather statement, Jul 10, 12:36 PM MST, 4 hours 40 minutes before

Special Weather Statement
National Weather Service Flagstaff AZ
136 PM MDT Sat Jul 10 2021

AZZ011-040-102000-
Chuska Mountains and Defiance Plateau-
Northeast Plateaus and Mesas South of Hwy 264-
136 PM MDT Sat Jul 10 2021

...SIGNIFICANT WEATHER ADVISORY FOR A STRONG THUNDERSTORM OVER
APACHE COUNTY AND THE NAVAJO NATION UNTIL 200 PM MDT...

At 134 PM MDT, Doppler radar was tracking a strong thunderstorm over
Wide Ruins moving south at 20 mph.

Nickel size hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Wide Ruins and parts of US Hwy 191 between Wide Ruins and Chambers.

LAT...LON 3551 10957 3550 10939 3530 10935 3533 10966
TIME...MOT...LOC 1934Z 004DEG 17KT 3543 10948

NL

Local storm report, Jul 10, 1:12 PM MST, 4 hours 4 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
112 PM MST SAT JUL 10 2021

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

0707 PM     HAIL             1 NW HEBER-OVERGAARD    34.43N 110.58W
07/09/2021  M1.00 INCH       NAVAJO             AZ   PUBLIC

&&

Special weather statement, Jul 10, 1:57 PM MST, 3 hours 19 minutes before

Special Weather Statement
National Weather Service Flagstaff AZ
157 PM MST Sat Jul 10 2021

AZZ018-102130-
Northern Gila County-
157 PM MST Sat Jul 10 2021

...SIGNIFICANT WEATHER ADVISORY FOR A STRONG THUNDERSTORM IN GILA
COUNTY INCLUDING AREAS NEAR CANYON DAY UNTIL 230 PM MST...

At 156 PM MST, Doppler radar was tracking a strong thunderstorm near
Fort Apache and Canyon Day, or 32 miles south of Show Low, moving
west at 15 mph.

Nickel size hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Whiteriver, Fort Apache Reservation and Canyon Day.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3380 11029 3386 11000 3367 11000 3364 11009
TIME...MOT...LOC 2056Z 077DEG 11KT 3377 11005

NL

Special weather statement, Jul 10, 2:55 PM MST, 2 hours 21 minutes before

Special Weather Statement
National Weather Service Flagstaff AZ
255 PM MST Sat Jul 10 2021

AZZ008-037-102245-
Yavapai County Valleys and Basins-Yavapai County  Mountains-
255 PM MST Sat Jul 10 2021

...SIGNIFICANT WEATHER ADVISORY FOR STRONG THUNDERSTORMS IN YAVAPAI
COUNTY UNTIL 345 PM MST...

At 254 PM MST, Doppler radar was tracking strong thunderstorms along
a line extending from 6 miles west of Paulden to near Yavapai County
Fairgrounds. Movement was west at 15 mph.

Half inch hail and wind gusts up to 50 mph will be possible with
these storms.

Locations impacted include...
Chino Valley, Prescott Valley, Prescott, Prescott Airport, Williamson
Valley, Prescott Gateway Mall, Iron Springs, Yavapai Campground,
Downtown Prescott, Ponderosa Park, Indian Hill West Prescott, Oak
Knoll Village, Lynx Lake Dam, Prescott Valley Event Center and White
Spar Campground.

LAT...LON 3482 11278 3445 11247 3461 11225 3470 11241
      3486 11256
TIME...MOT...LOC 2154Z 068DEG 15KT 3487 11258 3460 11232

NL

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 10, 5:09 PM MST	Severe Thunderstorm Warning	FGZ	Coconino, Gila, Yavapai	51 min
Jul 10, 5:56 PM MST	Severe Thunderstorm Warning	FGZ	Gila, Yavapai	49 min
Jul 10, 6:23 PM MST	Flash Flood Warning Considerable damage threat	FGZ	Gila, Navajo	3 hr
Jul 10, 6:44 PM MST	Severe Thunderstorm Warning	FGZ	Gila, Yavapai	35 min
Jul 11, 3:22 PM MST	Special Weather Statement	FGZ	Yavapai	23 min
Jul 11, 3:35 PM MST	Severe Thunderstorm Warning	FGZ	Yavapai	40 min
Jul 11, 3:49 PM MST	Severe Thunderstorm Warning	FGZ	Yavapai	41 min
Jul 11, 4:25 PM MST	Severe Thunderstorm Warning	FGZ	Yavapai	35 min
Jul 11, 4:46 PM MST	Severe Thunderstorm Warning	FGZ	Yavapai	29 min
Jul 11, 4:58 PM MST	Severe Thunderstorm Warning	FGZ	Yavapai	11 min

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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.