Alert archive / Arizona / Severe Thunderstorm Warnings in 2019

Severe Thunderstorm Warning 50, NWS Flagstaff, AZ

September 16, 2019Apache County, Navajo County, Arizona

NWS Flagstaff, AZ issued this severe thunderstorm warning at Sep 16, 2019, 12:35 PM MST for Apache County, Navajo County, Arizona. It was in force for 40 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued
Sep 16, 2019, 12:35 PM MST (19:35 UTC)
Expired
Sep 16, 2019, 1:15 PM MST
In force
40 min
Issued by
NWS Flagstaff, AZ
Area
Storm-based polygon
Hail
1.0 in
Wind
60.0 mph

Counties Apache County, AZ, Navajo County, AZ

The radar

The Flagstaff radar (KFSX), 149 km from the middle of the area, began a volume at 19:35 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, 7.6 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, Phoenix, AZ at 12:00Z on 2019-09-16Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 436 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, Phoenix, AZ at 12:00Z on 2019-09-16The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 56 square meters per square second.193958Sfc1 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
436 J/kg
Mixed-layer CIN
-185 J/kg
Mixed-layer LCL
2091 m above ground
0-6 km bulk shear
20 kt
0-1 km storm-relative helicity
56 m²/s²
0-3 km storm-relative helicity
98 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.1

Open this sounding in Storm Lab

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 Sep 16, 9:39 AM MST, 2 hours 56 minutes earlier.

Area forecast discussion, Sep 16, 9:39 AM MST, 2 hours 56 minutes before
Area Forecast Discussion
National Weather Service Flagstaff AZ
939 AM MST Mon Sep 16 2019

.SYNOPSIS...Moisture will remain in place across northern Arizona
today as a low pressure system moves into the Great Basin. The
result will be a chance for showers and thunderstorms through
this evening, along with strengthening southwest winds. Drier and
breezier conditions are forecast for Tuesday and Wednesday.

&&

.UPDATE...The trough moving onto the west coast this morning
continues to pull low-level moisture northward into central and
northern Arizona. Some isolated shower and thunderstorm activity
is already developing from around Prescott up to near Williams and
Bellemont. Still expecting storm coverage to increase into the
afternoon and early evening, with the highest coverage along/east
of a Prescott to Flagstaff to four corners line. Best instability
is forecast over Gila and southern Yavapai counties where a few
stronger storms with hail and gusty winds could develop. Winds at
the surface and aloft have increased this morning, and storms will
be moving toward the northeast at around 20 mph.

&&

.PREV DISCUSSION /352 AM MST/...Satellite indicates mid-level
clouds from about I-17/US 89 westward, with an area of lower
clouds near the New Mexico state line. Surface observations and
ADOT web cameras are indicating just lower clouds with no
appreciable fog, but patchy fog has been added to a few spots in
eastern Arizona through 8 am MST just in case it develops as the
low clouds dissipate.

For today...SPC mesoanalysis indicates an area of instability
across much of Yavapai County at present. Hi-res models indicate
the possibility of a few storms over this area through the
morning. Coverage of showers and storms is expected to increase
to the north and east after about noon, with some training storms
possible given the increase in southwesterly winds.

Tuesday and Wednesday...HREF mean QPF is much less on Tuesday than
on Monday, with a few storms possible in the afternoon but fairly
weak in nature given the expected drying. Southwest wind gusts to
around 35 mph are forecast along the Mogollon Rim and Coconino
Plateau on both Tuesday and Wednesday as another low pressure
system drops from the Pacific Northwest into the Great Basin.
Temperatures will be near to slightly above normal.

From Thursday onward...the strongest winds of the week are
forecast for Thursday with gusts in excess of 40 mph expected,
along with a chance for precipitation especially in eastern
Arizona. Cooler temperatures are expected Thursday as the trough
gets closer. Friday through Sunday, a general westerly flow is
expected with some weak disturbances perhaps moving through. Frost
and even some local freezing temperatures will be possible at high
elevations through this period. Low rain chances appear again
toward the early part of next week.

&&

.AVIATION...For the 18Z package...Isolated to scattered SHRA/TSRA
are expected through this evening with the higher coverage
along/east of a KPRC-KFLG-KOV7 line. Gusty winds to 35 kt and
decreased visibility near the strongest storms. Otherwise, VFR
conditions are forecast through 18z Tuesday. Aviation discussion not
updated for TAF amendments.

&&

.FIRE WEATHER...Moisture will remain over northern Arizona today with
a chance for showers and thunderstorms during the afternoon and
evening. Southwest winds will increase from today into Tuesday which
will promote drying. Much lower storm coverage is expected on
Tuesday.

Wednesday through Friday...Near critical fire weather conditions
will be possible across portions of northwestern Arizona Wednesday
and Thursday due to gusty southwest winds and low relative humidity.
A chance of precipitation returns Thursday to mainly eastern Arizona.
&&

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

&&

PUBLIC...JJ/AT
AVIATION...JJ
FIRE WEATHER...JJ

For Northern Arizona weather information visit
weather.gov/flagstaff

In the hours before

Special weather statement, Sep 16, 11:14 AM MST, 1 hour 21 minutes before
Special Weather Statement
National Weather Service Flagstaff AZ
1114 AM MST Mon Sep 16 2019

AZZ015-037-038-161845-
Yavapai County Valleys and Basins-Western Mogollon Rim-Oak Creek and
Sycamore Canyons-
1114 AM MST Mon Sep 16 2019

...SIGNIFICANT WEATHER ADVISORY FOR SEDONA IN YAVAPAI COUNTY AND
PORTIONS OF COCONINO COUNTIES UNTIL 1145 AM MST...

At 1112 AM MST, Doppler radar was tracking a strong thunderstorm near
Page Springs, or near Sedona, moving northeast at 25 mph.

Penny size hail and wind gusts up to 50 mph will be possible with
this storm.

Locations impacted include...
Sedona, Junipine Resort, Garland's Oak Creek Lodge, Slide Rock State
Park, Red Rock State Park, Manzanita Campground and West Fork Of Oak
Creek.

LAT...LON 3477 11194 3487 11201 3501 11177 3484 11164
TIME...MOT...LOC 1812Z 240DEG 22KT 3483 11188

ET
Special weather statement, Sep 16, 12:00 PM MST, 35 minutes before
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The office that day

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

IssuedProductOfficeCountiesLasted
Sep 16, 11:14 AM MSTSpecial Weather StatementFGZ31 min
Sep 16, 12:00 PM MSTSpecial Weather StatementFGZ30 min
Sep 16, 1:58 PM MSTSpecial Weather StatementFGZApache32 min
Sep 16, 2:07 PM MSTSevere Thunderstorm WarningFGZApache23 min
Sep 16, 4:33 PM MSTSpecial Weather StatementFGZYavapai27 min

Nearby

Severe Thunderstorm Warnings in Arizona, 2019Every severe thunderstorm warning in 2019

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.