Alert archive / Arizona / Flash Flood Watches in 2018

Flash Flood Watch 3, NWS Flagstaff, AZ

July 21, 2018Coconino County, Arizona

NWS Flagstaff, AZ issued this flash flood watch at Jul 21, 2018, 10:15 AM MST for Coconino County, Arizona. It took effect at Jul 21, 2018, 12:00 PM MST. It was in force for 8 hr.

The area

The counties it named.

The facts

Issued: Jul 21, 2018, 10:15 AM MST (17:15 UTC)
In effect from: Jul 21, 2018, 12:00 PM MST
Expired: Jul 21, 2018, 8:00 PM MST
In force: 8 hr
Issued by: NWS Flagstaff, AZ
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 17:17 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 12:00Z, 5.3 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: 232 J/kg
Mixed-layer CIN: -121 J/kg
Mixed-layer LCL: 1915 m above ground
0-6 km bulk shear: 18 kt
0-1 km storm-relative helicity: -13 m²/s²
0-3 km storm-relative helicity: 18 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 watch 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 watch went out at Jul 21, 3:53 AM MST, 6 hours 22 minutes earlier.

Area forecast discussion, Jul 21, 3:53 AM MST, 6 hours 22 minutes before

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In the hours before

Special weather statement, Jul 21, 10:00 AM MST, 15 minutes before

Special Weather Statement
National Weather Service Flagstaff AZ
1000 AM MST SAT JUL 21 2018

AZZ008-037-211730-
Yavapai County Valleys and Basins-Yavapai County  Mountains-
1000 AM MST SAT JUL 21 2018

...SIGNIFICANT WEATHER ADVISORY FOR YAVAPAI COUNTY FOR A STORM
OVER CONGRESS UNTIL 1030 AM MST...

At 959 AM MST, Doppler radar was tracking a strong thunderstorm over
Congress, or 14 miles northwest of Wickenburg, moving northwest at 30
mph.

Half inch hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Congress.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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.

&&

LAT...LON 3418 11274 3407 11285 3419 11316 3438 11300
TIME...MOT...LOC 1659Z 128DEG 25KT 3416 11286

JJ

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 20, 6:19 PM MST	Special Weather Statement	FGZ		41 min
Jul 20, 6:30 PM MST	Special Weather Statement	FGZ		45 min
Jul 20, 6:48 PM MST	Areal Flood Advisory	FGZ	Coconino	3 hr
Jul 20, 7:17 PM MST	Special Weather Statement	FGZ		43 min
Jul 21, 10:00 AM MST	Special Weather Statement	FGZ		30 min
Jul 21, 1:38 PM MST	Flash Flood Warning	FGZ	Coconino	3 hr
Jul 21, 1:51 PM MST	Special Weather Statement	FGZ		24 min
Jul 21, 2:18 PM MST	Special Weather Statement	FGZ		42 min
Jul 21, 3:01 PM MST	Special Weather Statement	FGZ	Coconino	29 min
Jul 21, 3:10 PM MST	Severe Thunderstorm Warning	FGZ	Coconino	50 min
Jul 21, 3:33 PM MST	Flash Flood Warning	FGZ	Coconino	2 hr
Jul 21, 3:49 PM MST	Special Weather Statement	FGZ		26 min

Nearby

Flash Flood Watches in Arizona, 2018 Every flash flood watch 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.