Special Weather Statement, NWS Flagstaff, AZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
302 PM MST Mon Aug 9 2021

.SYNOPSIS...Moisture will begin to increase today leading to
higher chances for thunderstorms through the week. There will be a
threat of localized flash flooding with the stronger storms.
Temperatures will decrease to near normal.

&&

.DISCUSSION...A couple of isolated storms have developed early
this afternoon across central Arizona. The rest of the state has
been capped so far due to morning cloud cover from the remnants
of an MCS in southern Arizona. Daytime heating and moisture being
pushed northward from that MCS will help to increase convective
activity later this afternoon into the evening hours. A boundary
of 500 J/Kg of ML CAPE extends along the Mogollon Rim so most
convection that occurs today will be along and south of the Rim.
The storms that have formed so far have been nearly stationary,
but weak steering flow will likely slowly move these storms to
the west this afternoon. Due to the slow storm motion, there is a
risk of flash flooding near stalled storms with heavy rain rates
of 0.5"-1" per hour. Storms in central Arizona may organize this
evening and form into a cluster that moves to the northwest late
tonight into the early morning hours. Storms on Tuesday will
extend north to the AZ/UT border as moisture surges northward from
southern Arizona. Increased cloud cover and moisture in the
region will bring temperatures down about 5 degrees from today
before increasing back to near average on Wednesday.

A weak ridge will remain in place across the region through at
least the middle of the week. A southerly low-level flow will
continue to bring moisture up from the Gulf of California into
northern Arizona. Isolated to scattered showers and storms will be
likely each day, with the greatest chance of storms south of I-40
where PW content will be greater. By late week, an inverted trough
may set-up to our east, increasing moisture flow and bringing
more favorable dynamics into the region. This would increase
precipitation coverage and the risk of flash flooding as well.

&&

.AVIATION...For the 0Z package...Mostly VFR conditions will exist
for the next 24 hours. MVFR conditions are possible through 0Z
tomorrow due to scattered showers and storms tonight through
tomorrow afternoon. The best likelihood for MVFR conditions
through 6Z tonight will be south of KFLG. On Tuesday, storms will
be more widespread so MVFR conditions are possible across northern
Arizona through evening. Through 0Z tomorrow, winds will be out
of the southwest at 5-10 knots with gusts of 15 knots Tuesday
afternoon. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Scattered storms will develop Tuesday and
Wednesday along and south of the Mogollon Rim with isolated storms
north of the Rim. Temperatures will decrease about 5 degrees on
Tuesday before increasing again on Wednesday.

Thursday through Saturday...Moisture will remain in place across
the region through at least Saturday. Scattered afternoon
thunderstorms are likely each day with the best chances for
precipitation south of I-40. Frequent lightning and isolated flash
flooding are expected with stronger storms that do form.

&&

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

&&

PUBLIC...DeMaria/Humphreys
AVIATION...DeMaria/Humphreys
FIRE WEATHER...DeMaria/Humphreys

For Northern Arizona weather information visit
weather.gov/flagstaff

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
406 PM MST MON AUG 9 2021

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

0405 PM     FLASH FLOOD      1 NE WALKER             34.47N 112.37W
08/09/2021                   YAVAPAI            AZ   TRAINED SPOTTER

            TRAINED SPOTTER REPORTED LYNX CREEK IN
            WALKER WAS RUNNING 4-5 FT DEEP IN SPOTS.

&&

TPS

Special Weather Statement
National Weather Service Flagstaff AZ
415 PM MST Mon Aug 9 2021

AZZ012-015-016-092345-
Little Colorado River Valley in Coconino County-Western Mogollon
Rim-Eastern Mogollon Rim-
415 PM MST Mon Aug 9 2021

...A strong thunderstorm will impact portions of Coconino County
south of Twin Arrows through 445 PM MST...

At 414 PM MST, Doppler radar was tracking a strong thunderstorm 7
miles south of Twin Arrows, or 22 miles southeast of Flagstaff,
moving south at 10 mph.

HAZARD...Wind gusts up to 50 mph and penny size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Ashurst Lake Campgrounds.

This includes Interstate 40 between mile markers 223 and 227.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

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

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 3512 11146 3515 11115 3489 11106 3483 11140
TIME...MOT...LOC 2314Z 352DEG 9KT 3505 11126

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...50 MPH

MCT

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