Severe Thunderstorm Warning 93, NWS Flagstaff, AZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
1049 AM 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 southwest of the Mogollon Rim
will see the most activity through the weekend. Some storms will
produce heavy rainfall, hail, and strong winds.

&&

.UPDATE...Forecast thinking is still on track with another active
monsoon thunderstorm day, particularly along and south of the
Mogollon Rim into Yavapai/Gila Counties where the greatest
moisture and instability reside. Clouds have mostly cleared out
this morning and won't inhibit daytime heating. Expect storms to
initiate along the Mogollon Rim/White Mountains, then drift
southwest late this afternoon and evening. The best potential for
strong to severe storms will be over Yavapai, Gila, and extreme
southwestern Coconino Counties where large hail and strong winds
will be possible. Areas of heavy rain are also likely but slightly
better steering flow should lessen the flash flood threat. North
of the Mogollon Rim, expect scattered storms with a bit more
coverage today than the past few days. Have adjusted precipitation
chances today based on expected trends. We've kept a chance for
storms in through the overnight hours as there is potential for
ongoing activity.

&&

.PREV DISCUSSION /434 AM MST/... Another active monsoon day is
expected again today. Satellite and surface analysis shows
significant increases in moisture across the high country as
dewpoints have generally increased into the mid 40s across region.
Locations along and south of the Mogollon Rim are currently
showing dewpoint values in the low to mid 50s.

Convection should initiate over the higher terrain, before moving
southwest through the afternoon and evening hours. The most
widespread area of activity is once again expected to be along the
Mogollon Rim and south where potential energy should be
maximized, and the higher terrain will create a trigger for
convection in the afternoon hours.

Unlike yesterday more convection is expected across the Little
Colorado River Valley, where moisture is beginning to make its
way back into the region from the previous days monsoonal storms.

Model soundings continue to show steep lapse rates that will allow
for a continued chance of large potentially damaging hail due to
significant amounts of convective energy at and above the hail
growth zone.

Dewpoint depressions near at the surface will continue to be
significant enough that convection especially at the lower
elevations could produce outflow winds with enough speed to be
potentially damaging.

Storm Motion is expected to be from the northeast to the southwest
at around 15 knots. This should slightly decrease the chance for
flash flooding, however storms over areas of enhanced flood risk
such as fire scars, along with storms that continue to remain over
an area for any prolonged period of time could still result in
flash flood warnings.

Models continue to show the large scale high pressure ridge
remaining over the area for the immediate future. Some model
guidance continues to show a downturn in monsoonal activity early
next week, but the details continue to shift at this point. Have
kept chances of precipitation in a typical diurnal monsoonal
pattern for the time being with moisture continuing to look
prevalent through the short term.

&&

.AVIATION...For the 18Z package...VFR conditions will continue
across most of northern Arizona for the next 24 hrs. Expect
scattered to numerous showers and thunderstorms to develop 20Z-05Z
along and to the south and west of the line KGCN-KFLG-KSOW-KSJN.
Expect isolated to scattered showers and thunderstorms north and
east of this line during this period. MVFR visibilities will be
possible under the stronger showers. Winds will be generally light
at 5-10 kts with afternoon gusts 10-20 kts, except in the vicinity
of strong storms where gusts above 40 knots are likely. In addition,
some storms will be capable of producing damaging hail. 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 today and
Saturday, 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.

Sunday through Tuesday...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/Suk
AVIATION...RR
FIRE WEATHER...MCT

For Northern Arizona weather information visit
weather.gov/flagstaff

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
1151 AM MST FRI AUG 10 2018

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

0430 PM     HAIL             PARKS                   35.26N 111.95W
08/09/2018  E1.00 INCH       COCONINO           AZ   TRAINED SPOTTER

            NICKEL TO QUARTER SIZE HAIL FELL FROM A
            SEVERE THUNDERSTORM THAT PASSED NEAR PARKS,
            AZ. HEAVY WATER PONDING WAS ALSO REPORTED
            FROM HEAVY RAINFALL ASSOCIATED WITH THIS
            STORM.

&&

NL

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