Alert archive / Arizona / Severe Thunderstorm Warnings in 2018

Severe Thunderstorm Warning 79, NWS Flagstaff, AZ

August 9, 2018Coconino County, Yavapai County, Arizona

NWS Flagstaff, AZ issued this severe thunderstorm warning at Aug 9, 2018, 3:08 PM MST for Coconino County, Yavapai County, Arizona. It was in force for 52 min. 4 reports 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: Aug 9, 2018, 3:08 PM MST (22:08 UTC)
Expired: Aug 9, 2018, 4:00 PM MST
In force: 52 min
Issued by: NWS Flagstaff, AZ
Area: Storm-based polygon
Hail: 1.25 in
Wind: 60.0 mph

Counties Coconino County, AZ, Yavapai County, AZ

The radar

The Flagstaff radar (KFSX), 78 km from the middle of the area, began a volume at 22:11 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
Aug 9, 3:08 PM MST	HAIL 1	1 Nne Flagstaff Airport, AZ
Aug 9, 3:10 PM MST	HAIL 1.25	1 N Flagstaff Airport, AZ	LARGEST STONES 1.25.SEVERAL ONE INCH STONES OBSERVED.
Aug 9, 3:10 PM MST	HAIL 1.5	1 N Flagstaff Airport, AZ	REPORTED AT 5078 S AMETHYST, FLAGSTAFF, AZ.
Aug 9, 3:20 PM MST	HAIL 1	4 Ese Bellemont (Nws Fl, AZ	OBSERVED 1 INCH HAIL ON I-40 1/2 MILE WEST OF EXIT 190.

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 5 storm reports to this severe thunderstorm warning; the first came 0 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 nearest sounding before it

Flgstf/Belemont, AZ (KFGZ), launched 12:00Z, 10.1 hours before the alert went out and 13 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: 399 J/kg
Mixed-layer CIN: -248 J/kg
Mixed-layer LCL: 1615 m above ground
0-6 km bulk shear: 12 kt
0-1 km storm-relative helicity: 130 m²/s²
0-3 km storm-relative helicity: 172 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.4

Open this sounding in Storm Lab

The text

As transmitted.

509 
WUUS55 KFGZ 092208
SVRFGZ
AZC005-025-092300-
/O.NEW.KFGZ.SV.W.0079.180809T2208Z-180809T2300Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Flagstaff AZ
308 PM MST THU AUG 9 2018

The National Weather Service in Flagstaff has issued a

* Severe Thunderstorm Warning for...
  Yavapai County in west central Arizona...
  Coconino County in north central Arizona...

* Until 400 PM MST

* At 308 PM MST, a severe thunderstorm was located near Downtown
  Flagstaff, moving west at 10 mph.

  HAZARD...60 mph wind gusts and half dollar size hail. 

  SOURCE...Radar indicated. 

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

* Locations impacted include...
  Flagstaff, Bellemont, Mountainaire, Downtown Flagstaff, Kachina
  Village, Cave Springs Campground, Pine Flat Campground, Sterling
  Fish Hatchery, West Fork Of Oak Creek and Canyon Vista Campground.

This includes the following highways...
 Route 66 between mile markers 192 and 198.
 Interstate 40 between mile markers 183 and 199.
 Interstate 17 between mile markers 328 and 339.
 State Route 89A between mile markers 384 and 398.
 Highway 180 between mile markers 217 and 219.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3523 11162 3506 11157 3495 11180 3528 11187
TIME...MOT...LOC 2208Z 078DEG 9KT 3516 11170 

HAIL...1.25IN
WIND...60MPH
 
$$

RR

1 follow-up statement

894 
WWUS55 KFGZ 092212
SVSFGZ

Severe Weather Statement
National Weather Service Flagstaff AZ
312 PM MST THU AUG 9 2018

AZC005-025-092300-
/O.CON.KFGZ.SV.W.0079.000000T0000Z-180809T2300Z/
Yavapai-Coconino-
312 PM MST THU AUG 9 2018

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 400 PM MST
FOR YAVAPAI AND COCONINO COUNTIES...

At 311 PM MST, a severe thunderstorm was located near Kachina
Village, or near Flagstaff, moving west at 10 mph.

HAZARD...60 mph wind gusts and half dollar size hail. 

SOURCE...Trained weather spotters. 

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

Locations impacted include...
Flagstaff, Bellemont, Mountainaire, Downtown Flagstaff, Kachina
Village, Cave Springs Campground, Pine Flat Campground, Sterling Fish
Hatchery, West Fork Of Oak Creek and Canyon Vista Campground.

This includes the following highways...
 Route 66 between mile markers 192 and 198.
 Interstate 40 between mile markers 183 and 199.
 Interstate 17 between mile markers 328 and 339.
 State Route 89A between mile markers 384 and 398.
 Highway 180 between mile markers 217 and 219.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3523 11162 3506 11157 3495 11180 3528 11187
TIME...MOT...LOC 2211Z 078DEG 9KT 3516 11171 

HAIL...1.25IN
WIND...60MPH
 
$$

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 Aug 9, 2:39 PM MST, 29 minutes earlier.

Area forecast discussion, Aug 9, 2:39 PM MST, 29 minutes before

Area Forecast Discussion
National Weather Service Flagstaff AZ
239 PM MST Thu Aug 9 2018

.SYNOPSIS...Deep moisture will continue to persist over central
and southern Arizona, bringing afternoon and evening showers and
thunderstorms to much of the area. Areas along and southwest of
the Mogollon Rim will see the most activity through the weekend.
Some storms will produce heavy rainfall, hail, and strong winds.

&&

.DISCUSSION...Current surface analysis shows dewpoints in excess
of 50 as far north as the Grand Canyon, and extending along the
and south of the Mogollon Rim where deeper moisture resides.
Mesoscale analyses currently indicate CAPE in excess of 2000J/kg
over and south of the Mogollon Rim, and expect robust convection
to continue developing as we exceed our convective temperature.
Storms should build rapidly over the Mogollon Rim, and move to the
south and west during the late afternoon and evening with the
5-10kt steering flow. Steep lapse rates and deeply mixed boundary
layer indicated in the forecast soundings will promote strong
winds with our storms this afternoon and evening. Severe winds,
hail, and and heavy rain will be the primary threat with storms.
One complicating factor overnight will be the circulation (weak
shortwave) currenly near the Four Corners moving southward on the
backside of the ridge - this may serve to amplify convection over
eastern Arizona this evening and overnight.

In general, little change in the pattern will be observed through
the weekend, with ample moisture in place and weak flow aloft. A
trough moving across the Pacific NW will decrease the amplitude of
the ridge over the Great Basin, but keep us with light steering
flow from the north or northeast. This, and some drier air working
in from the east late on the weekend, should keep the greatest
storm threat along and south of the Mogollon Rim.

Typical monsoon season thunderstorm activity will continue next
week. There are some indications that drier air may continue to be
ingested into the area and suppress thunderstorm activity early
next week, but it's really too soon to say with confidence.

&&

.AVIATION...Expect scattered to numerous showers and
thunderstorms to continue along and south of a line from KGCN-
KFLG-KSOW-KSJN, moving to the south and west through Yavapai and
northern Gila counties this evening. These storms will produce
outflow winds between 30 to 40 knots, and MVFR visibilities in
heavy rain. Isolated thunderstorms expected over northeast AZ.
Thunderstorm activity will diminish late tonight, and redevelop
over the higher terrain after 18Z Friday. Aviation discussion not
updated for TAF amendments.

&&

.FIRE WEATHER...Deep moisture will remain in place along and
south of the Mogollon Rim and White Mountains. Expect scattered to
numerous showers and thunderstorms in these areas Friday and
Saturday, with scattered storms mainly over the higher terrain north
of the Mogollon Rim. Strong outflow winds, heavy rainfall, hail,
and frequent lightning are the primary hazards.

Sunday through Tuesday...Expect scattered afternoon and evening
thunderstorms through the period, with the best chances for
storms continuing to be along the south of the Mogollon Rim and
White Mountains.

&&

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

&&

PUBLIC...BAK
AVIATION...BAK/RR
FIRE WEATHER...BAK/RR

For Northern Arizona weather information visit
weather.gov/flagstaff

In the hours before

Local storm report, Aug 9, 11:03 AM MST, 4 hours 5 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
1103 AM MST THU AUG 9 2018

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

0648 PM     TSTM WND GST     HUMBUG CREEK            34.11N 112.30W
08/08/2018  M75 MPH          YAVAPAI            AZ   MESONET

            MESONET STATION QHBA3, HUMBUG CREEK.

&&

41

Local storm report, Aug 9, 11:05 AM MST, 4 hours 3 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
1105 AM MST THU AUG 9 2018

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

0553 PM     TSTM WND GST     SUNSET POINT            34.19N 112.13W
08/08/2018  M56 MPH          YAVAPAI            AZ   MESONET

            MESONET STATION QSPA3, SUNSET POINT.

&&

41

Local storm report, Aug 9, 11:06 AM MST, 4 hours 2 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
1106 AM MST THU AUG 9 2018

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

0802 PM     TSTM WND GST     GRAND CANYON AIRPORT    35.95N 112.15W
08/08/2018  M52 MPH          COCONINO           AZ   ASOS

            ASOS STATION GCN, GRAND CANYON AIRPORT.

&&

41

Local storm report, Aug 9, 1:10 PM MST, 1 hour 58 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
110 PM MST THU AUG 9 2018

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

0145 AM     LIGHTNING        COTTONWOOD              34.74N 112.02W
08/09/2018                   YAVAPAI            AZ   BROADCAST MEDIA

            HOUSE CAUGHT FIRE DUE TO LIGHTNING STRIKE.
            NO INJURIES.

&&

41

Special weather statement, Aug 9, 2:03 PM MST, 1 hour 5 minutes before

Special Weather Statement
National Weather Service Flagstaff AZ
203 PM MST THU AUG 9 2018

AZZ015-092130-
Western Mogollon Rim-
203 PM MST THU AUG 9 2018

...SIGNIFICANT WEATHER ADVISORY FOR COCONINO COUNTY UNTIL 230 PM
MST...

At 202 PM MST, Doppler radar was tracking a strong thunderstorm over
Walnut Canyon National Monument, or near Flagstaff, moving south at
10 mph.

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

Locations impacted include...
Cosnino, Mountainaire, Walnut Canyon National Monument, Upper Lake
Mary, Upper Lake Mary Boat Ramps, Walnut Canyon Visitors Center,
Pinegrove Campground, Lower Lake Mary, Canyon Vista Campground, Lake
View Campground and Ashurst Lake Campgrounds.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3524 11153 3523 11144 3501 11140 3506 11169
TIME...MOT...LOC 2102Z 010DEG 11KT 3518 11150

RR

Local storm report, Aug 9, 2:36 PM MST, 32 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
236 PM MST THU AUG 9 2018

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

0220 PM     HAIL             4 S COSNINO             35.15N 111.48W
08/09/2018  E0.50 INCH       COCONINO           AZ   PARK/FOREST SRVC

            REPORT OF DIME-SIZED HAIL.

&&

DB

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 8, 5:43 PM MST	Severe Thunderstorm Warning	FGZ	Gila	47 min
Aug 8, 6:28 PM MST	Areal Flood Advisory	FGZ	Gila	3 hr
Aug 9, 2:03 PM MST	Special Weather Statement	FGZ		27 min
Aug 9, 2:39 PM MST	Severe Thunderstorm Warning	FGZ	Coconino	51 min
Aug 9, 2:58 PM MST	Severe Thunderstorm Warning	FGZ	Coconino	32 min
Aug 9, 3:03 PM MST	Areal Flood Advisory	FGZ	Coconino	111 min
Aug 9, 3:31 PM MST	Severe Thunderstorm Warning	FGZ	Coconino, Yavapai	29 min
Aug 9, 3:33 PM MST	Severe Thunderstorm Warning	FGZ	Navajo	30 min
Aug 9, 3:41 PM MST	Severe Thunderstorm Warning	FGZ	Coconino, Yavapai	49 min
Aug 9, 4:03 PM MST	Severe Thunderstorm Warning	FGZ	Coconino	57 min
Aug 9, 4:08 PM MST	Severe Thunderstorm Warning	FGZ	Coconino, Yavapai	67 min
Aug 9, 4:24 PM MST	Areal Flood Advisory	FGZ	Coconino, Yavapai	3 hr
Aug 9, 4:41 PM MST	Flash Flood Warning	FGZ	Gila	3 hr
Aug 9, 4:42 PM MST	Severe Thunderstorm Warning	FGZ	Yavapai	48 min
Aug 9, 4:58 PM MST	Severe Thunderstorm Warning	FGZ	Coconino, Yavapai	47 min

Nearby

Severe Thunderstorm Warnings in Arizona, 2018 Every severe thunderstorm warning in 2018

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.