Alert archive / Arizona / Severe Thunderstorm Warnings in 2018

Severe Thunderstorm Warning 177, NWS Flagstaff, AZ

September 2, 2018Navajo County, Arizona

NWS Flagstaff, AZ issued this severe thunderstorm warning at Sep 2, 2018, 6:44 PM MDT for Navajo County, Arizona. It was in force for 19 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 2, 2018, 6:44 PM MDT (00:44 UTC)
Expired: Sep 2, 2018, 7:03 PM MDT
In force: 19 min
Issued by: NWS Flagstaff, AZ
Area: Storm-based polygon
Hail: 1.0 in
Wind: 50.0 mph

County Navajo County, AZ

The radar

The Flagstaff radar (KFSX), 122 km from the middle of the area, began a volume at 00:44 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 00:00Z, 0.7 hours before the alert went out and 266 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: 189 J/kg
Mixed-layer CIN: -59 J/kg
Mixed-layer LCL: 2835 m above ground
0-6 km bulk shear: 15 kt
0-1 km storm-relative helicity: 12 m²/s²
0-3 km storm-relative helicity: 16 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

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 2, 3:26 PM MDT, 3 hours 18 minutes earlier.

Area forecast discussion, Sep 2, 3:26 PM MDT, 3 hours 18 minutes before

Area Forecast Discussion
National Weather Service Flagstaff AZ
226 PM MST Sun Sep 2 2018

.SYNOPSIS...The chance for showers and thunderstorms will continue
through the early part of this week. Thunderstorms will be most
numerous from the Mogollon Rim northward. Otherwise, expect cool
mornings and near normal high temperatures through the period. A
drying trend is expected toward the end of the week.

&&

.DISCUSSION...
More showers and thunderstorms have developed again this afternoon.
A notable weakening in the flow aloft today has transitioned us
toward more of a flash flood threat than the severe weather we
saw yesterday. This weak flow aloft will result in less shear and
slow storm motion promoting the threat of heavy rainfall and
flash flooding. These slower-moving storms are expected to
develop each day through at least Tuesday.

Eventually, warmer temperatures aloft develop as high pressure and
drier westerly flow forms off the California coast, and we expect
a drying and warming trend toward the end of the week.

&&

.AVIATION...For the 00Z package...Scattered thunderstorms will
continue into this evening, especially along and north of the
Mogollon Rim. MVFR/IFR conditions along with gusty and erratic
winds are possible near thunderstorms. Storm coverage is likely to
decrease overnight. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...Anticipate scattered showers and thundertorms,
mainly across higher terrain features, again Monday and Tuesday.

Wednesday through Friday...A significant downward trend in showers
and thunderstorms is forecast, with daytime temperatures climbing
back to near or slightly above normal values.

&&

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

&&

PUBLIC...KD/TPS
AVIATION...KD
FIRE WEATHER...KD

For Northern Arizona weather information visit
weather.gov/flagstaff

In the hours before

Local storm report, Sep 2, 4:00 PM MDT, 2 hours 44 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
300 PM MST SUN SEP 2 2018

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

1040 AM     HAIL             SAINT MICHAELS          35.66N 109.09W
09/01/2018  E1.75 INCH       APACHE             AZ   PUBLIC

            PUBLIC REPORT VIA SOCIAL MEDIA OF GOLF BALL
            AND HALF-DOLLAR SIZE HAIL FROM A SEVERE
            THUNDERSTORM PASSING OVER THEIR LOCATION.

&&

NL

Local storm report, Sep 2, 6:12 PM MDT, 32 minutes before

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Special weather statement, Sep 2, 6:27 PM MDT, 17 minutes before

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<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
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The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 2, 6:27 PM MDT	Special Weather Statement	FGZ	Navajo	33 min
Sep 3, 1:05 PM MDT	Special Weather Statement	FGZ		40 min
Sep 3, 2:38 PM MDT	Special Weather Statement	FGZ		52 min
Sep 3, 2:52 PM MDT	Flash Flood Warning	FGZ	Coconino, Gila	3 hr
Sep 3, 3:06 PM MDT	Special Weather Statement	FGZ		39 min
Sep 3, 3:10 PM MDT	Special Weather Statement	FGZ		50 min
Sep 3, 3:22 PM MDT	Severe Thunderstorm Warning	FGZ	Coconino	22 min
Sep 3, 4:09 PM MDT	Flash Flood Warning	FGZ	Coconino, Gila	3 hr
Sep 3, 4:54 PM MDT	Flash Flood Warning	FGZ	Gila	3 hr

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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.