Severe Thunderstorm Warning 70, NWS Flagstaff, AZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
931 AM MST Wed Aug 8 2018

.SYNOPSIS...High pressure over the state will produce another hot
afternoon, with high temperatures 5 to 10 degrees above normal.
Deeper moisture has returned to areas along and south of the
Mogollon Rim, thus look for increasing chances for showers and
thunderstorms through this weekend.

&&

.UPDATE...
Last nights low level moisture surge mentioned below has made it
to Tusayan, as their 9 am surface dew point is 53 degrees.
Deeper moisture and better instability are along and south of the
Mogollon Rim, and per the HRRR model it looks like storms today to
form along the Mogollon Rim with coverage increasing across
yavapai county late this afternoon and evening. The Four Corners
and areas along the Utah border expect hot conditions and the Heat
Warning will continue through 8 pm tonight. The short term
forecast is in good shape with no planned updates.

&&

.PREV DISCUSSION /349 AM MST/...There was a weak surge of moisture
into Yavapai and Gila counties on Tuesday morning that led to an
increase in thunderstorm coverage in these areas Tuesday
afternoon. A much stronger northward surge of moisture has
occurred overnight. This time the moisture has reached quite a bit
farther north, to at least Flagstaff. Surface dewpoints have risen
into the 60s in Yavapai and Gila counties and to the 50s along the
Mogollon Rim (up from the 30s earlier in the day). Forecast models
had a fairly good handle on this increase for that past day or
two, and remain consistent this morning. Strong mid level high
pressure will be parked over northern Arizona today, with light
steering flow. We expect the moisture increase to be sufficient
for scattered thunderstorms to develop by early afternoon along
the higher terrain from the Mogollon Rim to the White Mountains.
Light easterly steering flow should push these storms into Gila
and Yavapai counties during the mid afternoon to mid evening time
frame. With the deepest moisture and highest instability in these
areas, some of the storms could become strong and possibly severe,
with heavy rain and localized flooding. This pattern looks to
repeat over the next several days. On Thursday, the steering flow
will be slightly stronger so storms will be should easily be able
to move south from the rim country into the lower terrain. Even
higher instability is forecast Thursday afternoon in Yavapai/Gila,
so this is currently looking like the most favorable day for
strong storms and localized flooding. Little change in the overall
pattern is forecast Friday into the weekend. However, enough
moisture should work northward to bring some isolated to scattered
storms to areas north of the Mogollon Rim including Navajo Nation
and the Grand Canyon region. It will remain very hot over far
northern Arizona today and an Excessive Heat Warning continues for
the Grand Canyon and Lake Powell areas below 4000 feet elevation
where temperatures of 105-112 are expected.

&&

.AVIATION...For the 18Z package...VFR conditions will continue
across most of northern Arizona for the next 24 hrs. Local MVFR
visibility possible due to smoke from area wildfires. Winds will be
generally southwest to northwest at 5-10 kts with afternoon gusts 10-
20 kts. Stronger winds possible near any storms. Expect showers and
thunderstorms to develop along the line from KFLG-KSOW-KSJN after
19Z, before moving southward into northern Gila and Yavapai Counties
this afternoon and evening. Strong outflow winds above 40 knots will
be possible with these storms, most likely from the north or
northeast. In addition, MVFR visibilities will be possible in heavy
rainfall. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Monsoon moisture will continue to increase
today and Thursday from the Mogollon Rim and White Mountains
southward, and into Yavapai County. This will lead to an increasing
chance for showers and thunderstorms with a few storms becoming
strong by Thursday. Areas north of the Mogollon Rim to the Utah
border will remain dry.

Friday through Sunday...The Mogollon Rim, White Mountains and
regions and south will continue to see an increase in shower and
thunderstorm activity. From the Mogollon Rim and northward to the
Utah border, increasing moisture will lead to chances of
thunderstorms again Saturday and Sunday.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...Excessive Heat Warning until 8
PM MST this evening FOR AZZ005- 006.

&&

PUBLIC...DL/JJ
AVIATION...RR
FIRE WEATHER...MAS

For Northern Arizona weather information visit
weather.gov/flagstaff

Special Weather Statement
National Weather Service Flagstaff AZ
113 PM MST WED AUG 8 2018

AZZ015-038-082100-
Western Mogollon Rim-Oak Creek and Sycamore Canyons-
113 PM MST WED AUG 8 2018

...SIGNIFICANT WEATHER ADVISORY FOR COCONINO COUNTY UNTIL 200 PM
MST...

At 112 PM MST, Doppler radar was tracking a strong thunderstorm over
Mountainaire, or 9 miles southwest of Flagstaff, moving south at 10
mph.

Half inch hail and winds in excess of 30 mph will be possible with
this storm.

Locations impacted include...
Kachina Village...Mountainaire and I-17 between thesee points.

LAT...LON 3504 11165 3503 11177 3514 11167 3509 11161
TIME...MOT...LOC 2012Z 016DEG 9KT 3507 11169

41

Special Weather Statement
National Weather Service Flagstaff AZ
203 PM MST WED AUG 8 2018

AZZ015-037-038-082200-
Yavapai County Valleys and Basins-Western Mogollon Rim-Oak Creek and
Sycamore Canyons-
203 PM MST WED AUG 8 2018

...SIGNIFICANT WEATHER ADVISORY FOR YAVAPAI AND COCONINO COUNTIES
UNTIL 300 PM MST...

At 202 PM MST, Doppler radar was tracking a line of strong
thunderstorm over Junipine Resort, or 8 miles north of Sedona,
moving southwest at 10 mph.

Winds in excess of 40 mph will be possible with this storm.

Locations impacted include...
Sedona, Junipine Resort, Garland's Oak Creek Lodge, Slide Rock State
Park, Cave Springs Campground, Pine Flat Campground, Manzanita
Campground, Sterling Fish Hatchery and West Fork Of Oak Creek.

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.

&&

LAT...LON 3510 11176 3506 11170 3481 11175 3489 11198
TIME...MOT...LOC 2102Z 041DEG 11KT 3498 11180

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
247 PM MST WED AUG 8 2018

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

0233 PM     HAIL             7 W SLIDE ROCK          34.94N 111.87W
08/08/2018  E0.88 INCH       YAVAPAI            AZ   PARK/FOREST SRVC

            HAIL STONE APPEARED TO BE IN BETWEEN THE
            SIZE OF A QUARTER AND A NICKEL.

&&

RR