Severe Thunderstorm Warning 161, NWS Flagstaff, AZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
315 PM MST Sun Aug 26 2018

.SYNOPSIS...Isolated showers and thunderstorms will come to an end
during the evening hours. Starting Monday, drier air moving
across Arizona will lead to a significant downturn in shower and
thunderstorm activity through much of the coming week.

&&

.DISCUSSION...Over the coming days low pressure to the north of
Arizona combined with high pressure over Texas/New Mexico will
produce a drying southwest flow. The result will be a distinct
downturn in shower and thunderstorm activity across northern
Arizona this week.

The remainder of this afternoon and tonight...Monsoon moisture
will linger across northern Arizona resulting in isolated showers
and thunderstorms. Enough vertical wind shear and instability
exists for a few of these storms to become organized and severe
with the main threat being hail up to quarter size. All activity
is expected to come to an end by mid evening.

Monday through Friday...A drying southwest flow will become
established across northern Arizona. For the most part this drying
will spell the end for shower and thunderstorm activity across the
area. The only exception may be the White Mountains region where a
very slight chance of storms will continue on Monday and then
reemerge on Friday. The stronger southwest flow aloft will result
in breezy conditions at times through the week with the strongest
of these winds on Monday where gusts approaching 30 mph could be
observed. Otherwise, near normal temperatures and just a few
afternoon fair weather cumulus.

Labor Day weekend...Models are showing some moisture increase
across northern Arizona over the Labor Day weekend with even
deeper moisture just to the south. At this time models are showing
little to no shower or thunderstorm activity because the air mass
remains to dry in the lower levels and too warm aloft (stable
configuration). However, this time of year any hint toward a
moisture increase must be respected. Thus, we upped the chance for
showers and thunderstorms into the slight chance category for
Saturday, Sunday and Labor Day. If you have plans for the Labor
Day weekend, keep updated with the latest forecasts through the
week.

&&

.AVIATION...For the 00Z package...Mainly VFR conditions for the next
24 hours. Look for isolated thunderstorms ending by 03Z. For Monday,
expect mainly clear skies with southwest wind 10-20 kts gusting to
25 kts. A slight chance of a stray storm along the Arizona/New
Mexico border Monday afternoon. Aviation discussion not updated
for TAF amendments.

&&

.FIRE WEATHER...Much drier air will move across northern portions of
Arizona on Monday and Tuesday with only a slight chance of storms
over the White Mountains. Expect lower humidity and breezy afternoon
southwest winds both days.

Wednesday through Friday...A drier air mass will bring mostly clear
skies to northern Arizona. Other than a few afternoon fair weather
cumulus look for locally breezy southwest winds with temperatures
near normal for late August. A slight chance for showers and storms
will return to the White Mountains on Friday.

&&

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

&&

PUBLIC...McCollum
AVIATION...McCollum
FIRE WEATHER...McCollum

For Northern Arizona weather information visit
weather.gov/flagstaff

Special Weather Statement
National Weather Service Flagstaff AZ
1201 PM MST SUN AUG 26 2018

AZZ012-015-261930-
Little Colorado River Valley in Coconino County-Western Mogollon Rim-
1201 PM MST SUN AUG 26 2018

...SIGNIFICANT WEATHER ADVISORY FOR COCONINO COUNTY UNTIL 1230 PM
MST...

At 1200 PM MST, Doppler radar was tracking a strong thunderstorm near
Wupatki National Monument, or 28 miles north of Flagstaff, moving
northeast at 10 mph.

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

Locations impacted include...
Wupatki National Monument and Wupatki Visitors Center.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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 3547 11142 3556 11153 3573 11139 3559 11120
TIME...MOT...LOC 1900Z 218DEG 9KT 3557 11145

MCT

Special Weather Statement
National Weather Service Flagstaff AZ
145 PM MST SUN AUG 26 2018

AZZ009-012-013-040-262130-
Little Colorado River Valley in Navajo County-
Little Colorado River Valley in Coconino County-
Northeast Plateaus and Mesas Hwy 264 Northward-
Northeast Plateaus and Mesas South of Hwy 264-
145 PM MST SUN AUG 26 2018

...SIGNIFICANT WEATHER ADVISORY FOR NAVAJO AND COCONINO COUNTIES
UNTIL 230 PM MST...

At 145 PM MST, Doppler radar was tracking strong thunderstorms along
a line extending from near Tuba City to 9 miles west of Tolani Lake.
Movement was east at 10 mph.

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

Locations impacted include...
Tuba City, Tolani Lake, Coalmine Canyon Chapter House, Tonalea,
Moenkopi, Hopi and Hopi Reservation.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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 3635 11096 3538 11058 3538 11107 3611 11134
TIME...MOT...LOC 2045Z 271DEG 8KT 3607 11124 3548 11100

MCT

Special Weather Statement
National Weather Service Flagstaff AZ
258 PM MST SUN AUG 26 2018

AZZ006-007-262230-
Coconino Plateau-Grand Canyon Country-
258 PM MST SUN AUG 26 2018

...SIGNIFICANT WEATHER ADVISORY FOR COCONINO COUNTY UNTIL 330 PM
MST...

At 257 PM MST, Doppler radar was tracking a strong thunderstorm 15
miles northwest of Valle, or 33 miles southwest of Desert View at
Grand Canyon, moving east at 20 mph.

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

Locations impacted include...
Ten-x Campground.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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 3572 11232 3588 11237 3598 11198 3577 11193
TIME...MOT...LOC 2157Z 252DEG 17KT 3580 11234

MCT

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