Severe Thunderstorm Warning 99, NWS Flagstaff, AZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
328 PM MST Fri Aug 10 2018

.SYNOPSIS...Deep moisture will persist over central and southern
Arizona, bringing afternoon and evening showers and thunderstorms
to much of the area. Areas along and south of the Mogollon Rim
will see the most activity through the weekend. Some storms will
produce heavy rainfall, hail, and strong winds.

&&

.DISCUSSION...Afternoon convective thunderstorms have been slow to
develop today, but are underway along the Mogollon Rim, White
Mountains and northeastern plateaus and mesas. The deepest
monsoonal moisture remains banked up south of the Rim across Gila
and Yavapai Counties. Large scale high pressure remains stationed
to our northwest over the Great Basin keeping a mean steering flow
from the northeast to southwest. Winds aloft are slightly higher
today than yesterday, resulting in a slight increase in wind shear
favorable for some longer lived storms. Storms will continue to
develop over the high terrain and gradually move southwest this
evening. The high resolution models this afternoon show some
agreement with a more organized convective system moving through
central Arizona this evening and possibly into the overnight
hours, and we have trended the forecast in this direction.

The best potential for any severe storms or flash flooding will
be over Gila/Yavapai Counties where the deepest moisture and
instability are. Large hail and damaging wind are possible. Storm
motion should limit the flash flood threat in general, but areas
that receive multiple rounds of rainfall could experience
flooding.

The overall pattern remains relatively unchanged over the weekend
with storms favoring the Rim southward through the afternoon with
storms moving to the southwest. This will depend on nighttime
convection and how much lingering morning cloud cover exists.
Temperatures will remain near average for this time of year,
except for some of the northern valleys such as near Winslow and
Page that are quite warm due to the lack of shower activity.

It looks like early next week will see a thinning of moisture
resulting in less storm coverage, but moisture will increase
again by the middle of the week as a deeper southerly flow
develops.

&&

.AVIATION...For the 00Z package...Scattered to numerous
thunderstorms will continue this evening and possibly into the
overnight hours across northern Arizona. Storms will move to the
southwest through the evening hours. A few strong storms producing
40-50 kt winds and large hail are possible, mainly south of KFLG-KSOW.
Isolated IFR in +TSRA, with otherwise primarily VFR conditions
through the forecast period. Another round of scattered
thunderstorms is forecast for Saturday afternoon. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Deep moisture will remain in place along and
south of the Mogollon Rim and White Mountains. Expect scattered to
numerous showers and thunderstorms in these areas through the
weekend, with scattered storms mainly over the higher terrain
north of the Mogollon Rim to the Utah boarder. Strong outflow
winds, heavy rainfall, hail, and frequent lightning are the
primary hazards.

Monday through Wednesday...Expect scattered afternoon and evening
thunderstorms through the period, with the best chances for
storms continuing to be along the south of the Mogollon Rim and
White Mountains.

&&

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

&&

PUBLIC...MCT
AVIATION...MCT
FIRE WEATHER...MCT

For Northern Arizona weather information visit
weather.gov/flagstaff

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
159 PM MST FRI AUG 10 2018

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

0700 PM     FLASH FLOOD      7 WSW ASH FORK          35.20N 112.60W
08/09/2018                   YAVAPAI            AZ   TRAINED SPOTTER

            HEAVY RAINS CAUSED 6-8" OF FLOWING WATER
            ACROSS NORMALLY DRY RANCH LAND SEVEN MILES
            SOUTHWEST OF ASH FORK. EIGHTMILE CREEK WAS
            REPORTED TO BE OVERFLOWING THE CREEK BANKS
            SOUTH OF I-40.

&&

NL

Special Weather Statement
National Weather Service Flagstaff AZ
441 PM MST FRI AUG 10 2018

AZZ007-015-038-110015-
Coconino Plateau-Western Mogollon Rim-Oak Creek and Sycamore Canyons-
441 PM MST FRI AUG 10 2018

...SIGNIFICANT WEATHER ADVISORY FOR COCONINO COUNTY UNTIL 515 PM
MST...

At 440 PM MST, Doppler radar was tracking a strong thunderstorm just
northeast of Williams, or 26 miles west of Flagstaff, moving south
at 25 mph.

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

Locations impacted include...
Williams, Parks, Raymond Boy Scout Camp, Dogtown Lake Campground,
Kaibab Lake Campground and White Horse Lake Campground.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

LAT...LON 3542 11214 3534 11192 3507 11196 3518 11232
TIME...MOT...LOC 2340Z 017DEG 21KT 3526 11207

KD

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
549 PM MST FRI AUG 10 2018

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

0720 PM     TSTM WND DMG     PINETOP-LAKESIDE        34.13N 109.94W
08/09/2018                   NAVAJO             AZ   TRAINED SPOTTER

            8" DIAMETER FRUIT TREE WAS SNAPPED IN HALF
            DUE TO GUSTY WINDS ASSOCIATED WITH THE
            OUTFLOW OF A THUNDERSTORM IN THE VICINITY OF
            PINETOP-LAKESIDE.

&&

NL

Special Weather Statement
National Weather Service Flagstaff AZ
629 PM MST FRI AUG 10 2018

AZZ007-015-110200-
Coconino Plateau-Western Mogollon Rim-
629 PM MST FRI AUG 10 2018

...SIGNIFICANT WEATHER ADVISORY FOR COCONINO COUNTY UNTIL 700 PM
MST...

At 629 PM MST, Doppler radar was tracking a strong thunderstorm over
Valle, or 30 miles southwest of Desert View at Grand Canyon, moving
southwest at 5 mph.

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

Locations impacted include...
Valle.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

LAT...LON 3580 11209 3566 11198 3552 11214 3572 11231
TIME...MOT...LOC 0129Z 046DEG 6KT 3568 11212

KD

Special Weather Statement
National Weather Service Flagstaff AZ
641 PM MST FRI AUG 10 2018

AZZ008-018-037-110230-
Yavapai County Valleys and Basins-Northern Gila County-Yavapai County
Mountains-
641 PM MST FRI AUG 10 2018

...SIGNIFICANT WEATHER ADVISORY FOR GILA AND YAVAPAI COUNTIES UNTIL
730 PM MST...

At 640 PM MST, Doppler radar was tracking a strong thunderstorm 7
miles south of Pine, or 10 miles west of Payson, moving southwest at
10 mph.

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

Locations impacted include...
Tonto Natural Bridge State Park.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

LAT...LON 3440 11151 3427 11136 3412 11149 3431 11174
TIME...MOT...LOC 0140Z 046DEG 10KT 3429 11151

KD