Alert archive / Arizona / Flash Flood Warnings in 2018

Flash Flood Warning 105, NWS Flagstaff, AZ

August 21, 2018Coconino County, Arizona

NWS Flagstaff, AZ issued this flash flood warning at Aug 21, 2018, 9:07 PM MST for Coconino County, Arizona. It was in force for 5 hr. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Aug 21, 2018, 9:07 PM MST (04:07 UTC)
Expired: Aug 22, 2018, 2:00 AM MST
In force: 5 hr
Issued by: NWS Flagstaff, AZ
Area: Storm-based polygon
Flood severity: None

County Coconino County, AZ

The radar

The Flagstaff radar (KFSX), 150 km from the middle of the area, began a volume at 04:11 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.

The nearest sounding before it

Flgstf/Belemont, AZ (KFGZ), launched 00:00Z, 4.1 hours before the alert went out and 68 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: 256 J/kg
Mixed-layer CIN: -21 J/kg
Mixed-layer LCL: 1690 m above ground
0-6 km bulk shear: 11 kt
0-1 km storm-relative helicity: 11 m²/s²
0-3 km storm-relative helicity: 53 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 flash flood 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 flash flood warning went out at Aug 21, 8:52 PM MST, 15 minutes earlier.

Area forecast discussion, Aug 21, 8:52 PM MST, 15 minutes before

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In the hours before

Local storm report, Aug 21, 3:40 PM MST, 5 hours 27 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
340 PM MST TUE AUG 21 2018

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

0200 PM     FLASH FLOOD      BRIGHT ANGEL CREEK      36.12N 112.08W
08/21/2018                   COCONINO           AZ   PUBLIC

            HEAVY PRECIPITATION OVER THE NORTH RIM
            CREATED A FLASH FLOOD FOR BRIGHT ANGEL
            CREEK. THE EVENT WAS CAPTURED AND POSTED TO
            FACEBOOK VIA A PHOTO. TIME DELAY OF ABOUT
            1-2.5 HOURS FROM WHEN THE PRECIPITATION
            BEGAN TO WHEN THE PHOTO WAS CAPTURED.

&&

NL

Local storm report, Aug 21, 4:02 PM MST, 5 hours 5 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
402 PM MST TUE AUG 21 2018

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

0129 PM     FLASH FLOOD      BRIGHT ANGEL CREEK      36.12N 112.08W
08/21/2018                   COCONINO           AZ   PUBLIC

            CORRECTS PREVIOUS FLASH FLOOD REPORT FROM
            BRIGHT ANGEL CREEK. HEAVY PRECIPITATION OVER
            THE NORTH RIM CREATED A FLASH FLOOD FOR
            BRIGHT ANGEL CREEK. THE EVENT WAS CAPTURED
            AND POSTED TO FACEBOOK VIA A PHOTO.

&&

NL

Special weather statement, Aug 21, 4:20 PM MST, 4 hours 47 minutes before

Special Weather Statement
National Weather Service Flagstaff AZ
420 PM MST TUE AUG 21 2018

AZZ004-006-007-220000-
Kaibab Plateau-Coconino Plateau-Grand Canyon Country-
420 PM MST TUE AUG 21 2018

...SIGNIFICANT WEATHER ADVISORY FOR COCONINO COUNTY NEAR THE GRAND
CANYON UNTIL 500 PM MST...

At 419 PM MST, Doppler radar was tracking a strong thunderstorm over
South Rim Visitors Center, or 18 miles west of Desert View at Grand
Canyon, moving northeast at 20 mph.

Dime size hail and wind gusts of 50 to 55 mph will be possible with
this storm.

Locations impacted include...
Maricopa Point At Grand Canyon, Hermit's Rest At Grand Canyon,
Tusayan, Shoshone Point At Grand Canyon, Pima Point At Grand Canyon,
Bright Angel Point, Cape Royal At Grand Canyon, Hopi Point At Grand
Canyon, Yaqui Point At Grand Canyon, Grandview Point At Grand Canyon,
South Rim Visitors Center, Grand Canyon Village and Ten-x Campground.

LAT...LON 3592 11215 3606 11229 3628 11208 3609 11178
TIME...MOT...LOC 2319Z 231DEG 16KT 3605 11215

ET

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 21, 5:10 PM MST	Flash Flood Warning	FGZ	Coconino	3 hr
Aug 22, 3:40 AM MST	Flash Flood Watch	FGZ	Coconino	13 hr
Aug 22, 12:59 PM MST	Areal Flood Advisory	FGZ	Yavapai	5 hr
Aug 22, 2:07 PM MST	Special Weather Statement	FGZ		38 min
Aug 22, 2:36 PM MST	Areal Flood Advisory	FGZ	Coconino, Yavapai	3 hr
Aug 22, 4:39 PM MST	Flash Flood Warning	FGZ	Yavapai	3 hr
Aug 22, 4:48 PM MST	Flash Flood Warning	FGZ	Yavapai	3 hr

Nearby

Flash Flood Warnings in Arizona, 2018 Every flash flood 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.