Special Weather Statement, NWS Flagstaff, AZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
200 PM MST Fri Jul 23 2021

.SYNOPSIS...Continuous rounds of scattered to widespread showers
and thunderstorms can be expected through much of the weekend. As
a result, the threat of flash flooding as well as an isolated
strong to severe storm will remain. Storm coverage begins to
decrease early next week, becoming more isolated to scattered.

&&

.DISCUSSION...Widespread showers and thunderstorms will continue
over much of northern Arizona this afternoon. Flash flooding from
heavy rainfall is expected to be the primary threats with these
storms. However, with some destabilization occurring this
afternoon, a few isolated strong to severe thunderstorms will be
possible this afternoon and into the early evening hours.

An inverted trough over western Texas/New Mexico will continue to
propagate westward into Arizona this weekend. With significant
monsoonal moisture in place over much of Arizona, scattered to
widespread showers and thunderstorms are expected to continue
through much of the weekend. Significant flash flood threat is
expected to continue through the weekend over much of northern
Arizona, as a result, the Flash Flood Watch has been extended into
Sunday evening. With the increased synoptic-scale lift from the
approaching wave, nocturnal showers and thunderstorms are expected
each night through Sunday. Latest hi-res guidance has an MCS
developing this evening over eastern Arizona and pushing westward
across the state overnight resulting from the increase dynamic
support.

Saturday, with the trough moving westward across the state, the
greatest lift moves southeastward. Greatest potential for flash
flooding will then be for areas along and southwest of the
Mogollon Rim. Uncertainty still exists in exactly where the
greatest force will be in place on Sunday to support heavier
rainfall, but latest guidance continues the south and westward
shift.

For the start of next week, with Arizona now on the backside of
the trough, moisture looks to decrease slightly. As a result,
more isolated to scattered coverage is expected for the upcoming
week.

Temperatures are expected to remain cool through the weekend as
with the trough in place over Arizona. As it drifts west and ejects
into the Pacific early next week, temperatures begin to warm
slightly as heights begin to rise once again. Background winds are
also expected to remain light through the forecast period.

&&

.AVIATION...For the 00Z package...MVFR conditions are possible
through the TAF period with scattered to widespread showers and
thunderstorms expected. Brief IFR conditions will be possible in
some of the heavier showers. Gusty and erratic winds possible
near thunderstorms, with winds remaining light otherwise.
Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Significant flash flood potential exists through
Sunday night. Scattered to numerous showers and thunderstorms are
expected each afternoon this weekend, with storms also continuing
into the overnight hours. Widespread wetting rains are likely with
embedded areas of heavy rain. Storm coverage begins to decrease
for the first part of next week.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Sunday evening FOR AZZ006>008-011>018-
037-038-040.

&&

PUBLIC...Humphreys
AVIATION...Humphreys
FIRE WEATHER...Humphreys

For Northern Arizona weather information visit
weather.gov/flagstaff

Special Weather Statement
National Weather Service Flagstaff AZ
117 PM MST Fri Jul 23 2021

AZZ004-005-009-232100-
Kaibab Plateau-Marble and Glen Canyons-Northeast Plateaus and Mesas
Hwy 264 Northward-
117 PM MST Fri Jul 23 2021

...SIGNIFICANT WEATHER ADVISORY FOR COCONINO COUNTY INCLUDING PAGE
AND LAKE POWELL UNTIL 200 PM MST/300 PM MDT/...

At 116 PM MST/216 PM MDT/, Doppler radar was tracking strong
thunderstorms along a line extending from 9 miles east of Wahweap to
19 miles west of Big Water. Movement was southeast at 20 mph.

Pea size hail and winds in excess of 40 mph will be possible with
these storms.

Locations impacted include...
Page, Big Five, LeChee, Marble Canyon, Lees Ferry, Antelope Canyon
Near Sr 98, Antelope Creek Basin, Wahweap, Lake Powell, Antelope
Canyon and Waterholes Canyon.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with these storms, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3700 11121 3665 11094 3668 11199 3700 11210
TIME...MOT...LOC 2016Z 335DEG 21KT 3702 11133 3704 11202

JJ

Special Weather Statement
National Weather Service Flagstaff AZ
224 PM MST Fri Jul 23 2021

AZZ007-008-037-232200-
Yavapai County Valleys and Basins-Coconino Plateau-Yavapai County
Mountains-
224 PM MST Fri Jul 23 2021

...SIGNIFICANT WEATHER ADVISORY FOR YAVAPAI COUNTY SOUTH OF ASH FORK
UNTIL 300 PM MST...

At 223 PM MST, Doppler radar was tracking a strong thunderstorm 7
miles south of Ash Fork, or 24 miles north of Chino Valley, moving
south at 20 mph.

Penny size hail and winds in excess of 40 mph will be possible with
this storm.

This storm will remain over mainly rural areas of Yavapai and
Coconino Counties including Highway 89 south of Ash Fork.

LAT...LON 3519 11261 3521 11246 3501 11238 3495 11262
TIME...MOT...LOC 2123Z 357DEG 16KT 3511 11249

JJ

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
340 PM MST FRI JUL 23 2021

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

0300 PM     FLASH FLOOD      1 SSW PRESCOTT VALLEY   34.59N 112.33W
07/23/2021                   YAVAPAI            AZ   PUBLIC

            ROAD WASHED OUT DUE TO FLOODING.

&&

MD

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