Flash Flood Warning 104, NWS Flagstaff, AZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
341 PM MST Tue Aug 21 2018

.SYNOPSIS...Deep monsoon moisture will remain over northern
Arizona through Friday. This will result in good chances for
afternoon and evening thunderstorms each day. A slight downturn in
shower and thunderstorm activity is possible over the weekend and
early next week.

&&

.DISCUSSION...After an active morning and early afternoon when a
line of convection moved north through the region, much of the
area is quiet right now. There is still some shower and
thunderstorm activity across the White Mountains and northwest
Coconino County. Latest hi-res guidance indicates the activity
across Coconino County will progress toward the north and east
this evening with the primary threats as gusty winds and heavy
rainfall. Additionally, we have been tracking an MCV which is
currently located over Pima County. This is expected to continue
to track slowly toward the north and lead to additional shower and
thunderstorm development later this evening south of I-40. There
is the potential that convection associated with this feature
could reach as far north as the Flagstaff area, but confidence is
not high in the northward extent at this time. As was the case
last night, convection could persist into the overnight areas for
some locations.

Monsoonal moisture will remain entrenched over the region through
Friday leading to continued active conditions. While shower and
thunderstorm chances will continue over the weekend, there are
some indications of a downturn in the coverage. Long range model
guidance continues to struggle with the pattern evolution early
next week, but the first indications of fall are seen in some
models with troughs digging down toward the Southwest US. Stay
tuned.

&&

.AVIATION...For the 00z package...Shower and thunderstorm activity
will be most prevalent in the White Mountains and north of I-40
over the next few hours. Additional development is possible south
of I-40 after 01z. Some convection will likely persist into the
overnight hours. Storm motion will generally be toward the north
and east. Gusty winds and heavy rainfall will be the primary
threats. MVFR and IFR conditions will be possible with the
strongest storms. Another active monsoon day is anticipated
Wednesday with scattered to numerous shower and thunderstorm
development. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Ample monsoon moisture will remain in place over the
next few days with scattered to numerous thunderstorms each day.
Convection could persist into the late evening and overnight hours
especially through Thursday. Temperatures will remain at or slightly
below normal for late August. A slight downturn in thunderstorm
activity is possible over the weekend.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...Flash Flood Watch until 9 PM
MST this evening FOR AZZ004>007-009- 010-039.

&&

PUBLIC...TPS
AVIATION...TPS
FIRE WEATHER...TPS

For Northern Arizona weather information visit
weather.gov/flagstaff

Special Weather Statement
National Weather Service Flagstaff AZ
1146 AM MST TUE AUG 21 2018

AZZ009>011-039-211915-
Chuska Mountains and Defiance Plateau-Black Mesa Area-Northeast
Plateaus and Mesas Hwy 264 Northward-Chinle Valley-
1146 AM MST TUE AUG 21 2018

...SIGNIFICANT WEATHER ADVISORY FOR EXTREME NORTHERN APACHE AND
NAVAJO COUNTIES UNTIL 1215 PM MST...

At 1145 AM MST, Doppler radar was tracking strong thunderstorms along
a line extending from 15 miles northwest of Navajo National Monument
to 11 miles south of Totacon. Movement was northeast at 45 mph.

Dime size hail and wind gusts up to 50 mph will be possible with
these storms.

Locations impacted include...
Goulding, Rock Point, Red Mesa, Mexican Water, Monument Valley
Visitors Center, Totacon, Dennehotso and Teec Nos Pos.

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.

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 3698 10904 3664 10930 3697 11071 3700 11070
      3700 10905
TIME...MOT...LOC 1845Z 205DEG 40KT 3697 11062 3668 10939

JJ

Special Weather Statement
National Weather Service Flagstaff AZ
213 PM MST TUE AUG 21 2018

AZZ004-212200-
Kaibab Plateau-
213 PM MST TUE AUG 21 2018

...SIGNIFICANT WEATHER ADVISORY FOR COCONINO COUNTY UNTIL 300 PM
MST...

At 212 PM MST, Doppler radar was tracking a strong thunderstorm 14
miles east of Pipe Spring, or 14 miles south of Kanab, moving east at
20 mph.

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

Locations impacted include...
Jacob Lake, Fredonia and Jacob Lake Campground.

LAT...LON 3700 11206 3664 11213 3672 11262 3674 11262
      3674 11261 3678 11262 3681 11260 3683 11260
      3690 11257 3691 11255 3694 11254 3695 11253
      3698 11254 3700 11254
TIME...MOT...LOC 2112Z 279DEG 17KT 3682 11248

Suk

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
340 PM MST TUE AUG 21 2018

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

0200 PM     FLASH FLOOD      BRIGHT ANGEL CREEK      36.12N 112.08W
08/21/2018                   COCONINO           AZ   PUBLIC

            HEAVY PRECIPITATION OVER THE NORTH RIM
            CREATED A FLASH FLOOD FOR BRIGHT ANGEL
            CREEK. THE EVENT WAS CAPTURED AND POSTED TO
            FACEBOOK VIA A PHOTO. TIME DELAY OF ABOUT
            1-2.5 HOURS FROM WHEN THE PRECIPITATION
            BEGAN TO WHEN THE PHOTO WAS CAPTURED.

&&

NL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
402 PM MST TUE AUG 21 2018

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

0129 PM     FLASH FLOOD      BRIGHT ANGEL CREEK      36.12N 112.08W
08/21/2018                   COCONINO           AZ   PUBLIC

            CORRECTS PREVIOUS FLASH FLOOD REPORT FROM
            BRIGHT ANGEL CREEK. HEAVY PRECIPITATION OVER
            THE NORTH RIM CREATED A FLASH FLOOD FOR
            BRIGHT ANGEL CREEK. THE EVENT WAS CAPTURED
            AND POSTED TO FACEBOOK VIA A PHOTO.

&&

NL

Special Weather Statement
National Weather Service Flagstaff AZ
420 PM MST TUE AUG 21 2018

AZZ004-006-007-220000-
Kaibab Plateau-Coconino Plateau-Grand Canyon Country-
420 PM MST TUE AUG 21 2018

...SIGNIFICANT WEATHER ADVISORY FOR COCONINO COUNTY NEAR THE GRAND
CANYON UNTIL 500 PM MST...

At 419 PM MST, Doppler radar was tracking a strong thunderstorm over
South Rim Visitors Center, or 18 miles west of Desert View at Grand
Canyon, moving northeast at 20 mph.

Dime size hail and wind gusts of 50 to 55 mph will be possible with
this storm.

Locations impacted include...
Maricopa Point At Grand Canyon, Hermit's Rest At Grand Canyon,
Tusayan, Shoshone Point At Grand Canyon, Pima Point At Grand Canyon,
Bright Angel Point, Cape Royal At Grand Canyon, Hopi Point At Grand
Canyon, Yaqui Point At Grand Canyon, Grandview Point At Grand Canyon,
South Rim Visitors Center, Grand Canyon Village and Ten-x Campground.

LAT...LON 3592 11215 3606 11229 3628 11208 3609 11178
TIME...MOT...LOC 2319Z 231DEG 16KT 3605 11215

ET