Alert archive / Arizona / Special Weather Statements in 2021

Special Weather Statement, NWS Flagstaff, AZ

September 1, 2021

NWS Flagstaff, AZ issued this special weather statement at Sep 1, 2021, 6:52 PM MST. It was in force for 38 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
Sep 1, 2021, 6:52 PM MST (01:52 UTC)
Expired
Sep 1, 2021, 7:30 PM MST
In force
38 min
Issued by
NWS Flagstaff, AZ
Hail
0.50 in
Wind
40

The nearest sounding before it

Grand Junction, CO (KGJT), launched 00:00Z, 1.9 hours before the alert went out and 289 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-pSkew-T log-p diagram, Grand Junction, CO at 00:00Z on 2021-09-02Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 4 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Grand Junction, CO at 00:00Z on 2021-09-02The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -8 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
4 J/kg
Mixed-layer CIN
-101 J/kg
Mixed-layer LCL
863 m above ground
0-6 km bulk shear
43 kt
0-1 km storm-relative helicity
-8 m²/s²
0-3 km storm-relative helicity
63 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

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What forecasters said that day

The local office's own words before this special weather statement 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 special weather statement went out at Sep 1, 2:15 PM MST, 4 hours 37 minutes earlier.

Area forecast discussion, Sep 1, 2:15 PM MST, 4 hours 37 minutes before
Area Forecast Discussion
National Weather Service Flagstaff AZ
215 PM MST Wed Sep 1 2021

.SYNOPSIS...Scattered showers and thunderstorms will continue
through this afternoon. Some storms may bring heavy rainfall,
which could lead to flash flooding. Thunderstorm coverage will
decrease Thursday with much more limited coverage expected this
weekend. Cool temperatures through Friday will start a warming
trend through this weekend, continuing through the first half of
next week.

&&

.DISCUSSION...Wrap around moisture from an upper low is beginning
to move into western Coconino and Yavapai counties. Thunderstorms
are beginning to develop as a result. A few thunderstorms could
produce gusty winds and damaging hail, along with isolated flash
flooding. Will continue to monitor trends as these storms develop
through the late afternoon hours. As a result, will keep the
current Flash Flood Watch going for this forecast package.

Thunderstorms should diminish overnight with the loss of daytime
heating. However, lingering moisture and instability will
contribute to scattered thunderstorm development along the
Mogollon Rim and Bradshaw Mountains Thursday afternoon. Impacts
should be minimal.

The deepest moisture should then get swept into the White
Mountains Friday and Saturday, with afternoon thunderstorm chances
remaining confined to that area and dry conditions elsewhere.

High pressure is then forecast to rotate from southern California
into southern Nevada, then into Utah during the first half of next
week. This will allow for moisture to creep back northward along
the Mogollon Rim, with afternoon thunderstorm chances expected
each day over the higher terrain south of I-40. The high pressure
will also allow for a gradual warming trend during the first half
of next week.

&&

.AVIATION...For the 00z package...VFR with TEMPO MVFR conditions
near thunderstorms will be possible over northern Arizona terminal
aerodromes until about 02z. MVFR/IFR ceilings and visibilities
will be possible in patchy fog at high terrain terminals after 06z
Thursday. Scattered thunderstorms will then be possible near
KSEZ-KPRC-KFLG-KGCN Thursday afternoon. Aviation discussion not
updated for TAF amendments.

&&

.FIRE WEATHER...Scattered thunderstorms will develop over the
higher terrain Thursday afternoon. Drier conditions are forecast
for Friday, with a chance of thunderstorms confined to the White
Mountains Friday afternoon.

Saturday through Monday...There will be a chance for thunderstorms
along the Mogollon Rim and the Bradshaw Mountains each afternoon.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...Flash Flood Watch through late tonight FOR AZZ004>018-037>040.

&&

PUBLIC...TM
AVIATION...TM
FIRE WEATHER...TM

For Northern Arizona weather information visit
weather.gov/flagstaff

In the hours before

Special weather statement, Sep 1, 3:13 PM MST, 3 hours 39 minutes before
Special Weather Statement
National Weather Service Flagstaff AZ
413 PM MDT Wed Sep 1 2021

AZZ012-040-012245-
Little Colorado River Valley in Coconino County-
Northeast Plateaus and Mesas South of Hwy 264-
413 PM MDT Wed Sep 1 2021

...A strong thunderstorm will impact portions of Coconino County
through 445 PM MDT/345 PM MST/...

At 412 PM MDT/312 PM MST/, Doppler radar was tracking a strong
thunderstorm 9 miles southeast of Gray Mountain, or 30 miles south of
Tuba City, moving east at 20 mph.

HAZARD...Winds in excess of 40 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...
Wupatki National Monument.

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 3558 11138 3575 11143 3588 11099 3562 11091
TIME...MOT...LOC 2212Z 256DEG 17KT 3569 11132

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...40 MPH

DB
Special weather statement, Sep 1, 4:21 PM MST, 2 hours 31 minutes before
Special Weather Statement
National Weather Service Flagstaff AZ
521 PM MDT Wed Sep 1 2021

AZZ010-012345-
Chinle Valley-
521 PM MDT Wed Sep 1 2021

...A strong thunderstorm will impact portions of Apache and Navajo
Counties through 545 PM MDT...

At 520 PM MDT, Doppler radar was tracking a strong thunderstorm 9
miles north of Kayenta, or 26 miles southwest of Mexican Hat, moving
east at 20 mph.

HAZARD...Winds in excess of 30 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...
Goulding and Monument Valley Visitors Center.

This includes the following highways...
 Highway 163 between mile markers 398 and 416.
 Highway 160 between mile markers 407 and 413.

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.

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.

To report severe weather, contact your nearest law enforcement
agency. They will relay your report to the National Weather Service
office in Flagstaff.

&&

LAT...LON 3678 10991 3675 11031 3694 11037 3700 11018
      3700 10997
TIME...MOT...LOC 2320Z 256DEG 18KT 3686 11025

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...30 MPH

DB
Special weather statement, Sep 1, 5:10 PM MST, 1 hour 42 minutes before
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Special weather statement, Sep 1, 5:52 PM MST, 1 hour before
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Special weather statement, Sep 1, 6:17 PM MST, 35 minutes before
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Special weather statement, Sep 1, 6:52 PM MST, 0 minutes before
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The office that day

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

IssuedProductOfficeCountiesLasted
Sep 1, 5:00 PM MSTAreal Flood AdvisoryFGZCoconino2 hr
Sep 1, 5:10 PM MSTSpecial Weather StatementFGZ50 min
Sep 1, 5:42 PM MSTAreal Flood AdvisoryFGZApache, Navajo3 hr
Sep 1, 5:52 PM MSTSpecial Weather StatementFGZ38 min
Sep 1, 6:17 PM MSTSpecial Weather StatementFGZ43 min
Sep 2, 11:53 AM MSTSpecial Weather StatementFGZYavapai22 min
Sep 2, 1:24 PM MSTFlash Flood WarningFGZYavapai3 hr
Sep 2, 1:54 PM MSTFlash Flood Warning Considerable damage threatFGZYavapai51 min
Sep 2, 2:31 PM MSTAreal Flood AdvisoryFGZCoconino, Gila, Navajo3 hr
Sep 2, 2:48 PM MSTAreal Flood AdvisoryFGZCoconino3 hr
Sep 2, 3:39 PM MSTAreal Flood AdvisoryFGZCoconino111 min

Nearby

Special Weather Statements in Arizona, 2021Every special weather statement 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.