Special Weather Statement, NWS Flagstaff, AZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
959 AM MST Thu Aug 3 2017

.SYNOPSIS...Expect one more day of scattered thundertorms across
northern Arizona Today. A drier and more stable airmass will
bring much less storm coverage this weekend into early next week.

&&

.DISCUSSION...Morning satellite imagery shows cumulus development
beginning along the Mogollon Rim with more expansive cloud cover
to the south. The 12z RAOB from Bellemont this morning was a bit
more moist than yesterday with a precipitable water value of 0.88
inches. The 700-500mb lapse rate was also noticeably steeper than
yesterday indicating more CAPE available than the past few days
as well. We are expecting the most extensive convective
development to occur across the western Mogollon Rim with storms
moving generally to the north and northeast. The primary threat
will remain flash flooding and gusty outflow winds near
thunderstorms. Storm intensity and coverage will decrease after
sunset this evening.

A significant downward trend in showers and thunderstorms is still
on track for later this weekend and into next week as dry
southwesterly flow increases across the area.

&&

.PREV DISCUSSION /403 AM MST/...Moisture will be a limiting
factor for storm formation through the rest of the week, with
drier conditions expected through the weekend and into early next
week. Isentropic analysis shows moderate moisture remaining in the
region through Thursday evening allowing widespread storm
development. Southerly steering flow will allow for storms to
develop off the higher terrain such as the White Mountains,
Mogollon Rim, and Bradshaw Mountains before moving North-
Northeastward.

By Friday morning dry air associated with a low pressure system
off the California coast will begin to move into the Yavapai
county and should limit some storm development over the lower
terrain Friday. By Saturday the dry air looks to move into most of
the Northern Arizona. While some storms will still be possible
with this pattern, these storms are expected to be more widespread
and less efficient at producing heavy rainfall rates.

The dry air looks to be at its maximum extend Monday before an
easterly wave moves across the Four Corners region and re-
establishes a wetter monsoonal pattern by the later half of next
week. Confidence is not strong over the timing of this return to
wetter conditions, however model agreement in a return of
moisture does have chances of precipitation increasing in the
second half of next week.

&&

.AVIATION...For the 18Z package...Scattered showers and
thundertorms forming across the Mogollon Rim after 18z. Mostly
VFR conditions with MVFR and local IFR with the stronger storms.
Storms clearing after 02z. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...Expect scattered showers and thunderstorms today and
Friday with areas of moderate to locally heavy rain. Gusty winds
will develop near any storms.

Saturday through Monday...A general drying trend with daily chances
for showers and thunderstorms decreasing across northern Arizona,
near average temperatures are expected.

&&

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

&&

PUBLIC...TPS/Suk
AVIATION...ET
FIRE WEATHER...MAS

For Northern Arizona weather information visit
weather.gov/flagstaff

Hazardous Weather Outlook
National Weather Service Flagstaff AZ
407 AM MST Thu Aug 3 2017

AZZ004>018-037>040-040430-
Kaibab Plateau-Marble and Glen Canyons-Grand Canyon Country-
Coconino Plateau-Yavapai County Mountains-
Northeast Plateaus and Mesas Hwy 264 Northward-Chinle Valley-
Chuska Mountains and Defiance Plateau-
Little Colorado River Valley in Coconino County-
Little Colorado River Valley in Navajo County-
Little Colorado River Valley in Apache County-
Western Mogollon Rim-Eastern Mogollon Rim-White Mountains-
Northern Gila County-Yavapai County Valleys and Basins-
Oak Creek and Sycamore Canyons-Black Mesa Area-
Northeast Plateaus and Mesas South of Hwy 264-
407 AM MST Thu Aug 3 2017

This hazardous weather outlook is for Apache...Coconino...
Northern Gila...Navajo...and Yavapai Counties in Northern
Arizona.

.DAY ONE...Today and Tonight

The most likely initial development will be over the White
Mountains and Mogollon Rim later this morning, with storm motion
to the North and Northeast.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

Moisture begins to decrease across the area limiting storms to a
more isolated pattern through the weekend and into early next
week.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

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Special Weather Statement
National Weather Service Flagstaff AZ
1254 PM MST THU AUG 3 2017

AZZ008-037-032030-
Yavapai County Valleys and Basins-Yavapai County  Mountains-
1254 PM MST THU AUG 3 2017

...SIGNIFICANT WEATHER ADVISORY FOR THE CHERRY AREA OF YAVAPAI
COUNTY UNTIL 130 PM MST...

At 1254 PM MST, Doppler radar was tracking a strong thunderstorm near
Cherry, or 7 miles west of Camp Verde, moving northwest at 5 mph.

Nickel size hail will be possible with this storm.

Locations impacted include...
Cherry and Powell Springs Campground.

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 3454 11192 3451 11200 3459 11212 3466 11196
TIME...MOT...LOC 1954Z 144DEG 6KT 3456 11199

TM

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
101 PM MST THU AUG 3 2017

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

1145 AM     FLASH FLOOD      2 NE PRESCOTT COURTHOUS 34.56N 112.45W
08/03/2017                   YAVAPAI            AZ   MESONET

            USGS GAGE FOR THE GRANITE CREEK AT PRESCOTT
            (GCRA3) SHOWED A 4.42 FT. RISE IN 30 MINUTES
            (FROM 11:15AM TO 11:45AM).

&&

TM

Special Weather Statement
National Weather Service Flagstaff AZ
119 PM MST THU AUG 3 2017

AZZ007-032045-
Coconino Plateau-
119 PM MST THU AUG 3 2017

...SIGNIFICANT WEATHER ADVISORY FOR COCONINO COUNTY UNTIL 145 PM
MST...

At 118 PM MST, Doppler radar was tracking a strong thunderstorm near
Valle, or 37 miles southwest of Desert View at Grand Canyon. this
storm was nearly stationary.

Nickel size hail will be possible with this storm.

This storm will remain over mainly rural areas OF Coconino County.

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 3571 11216 3553 11214 3547 11237 3574 11240
TIME...MOT...LOC 2018Z 085DEG 2KT 3562 11224

KD

Special Weather Statement
National Weather Service Flagstaff AZ
221 PM MST THU AUG 3 2017

AZZ008-037-032200-
Yavapai County Valleys and Basins-Yavapai County  Mountains-
221 PM MST THU AUG 3 2017

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

At 220 PM MST, Doppler radar was tracking a strong thunderstorm over
Iron Springs, or 10 miles west of Prescott Valley, moving west at 5
mph.

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

Locations impacted include...
Yavapai Campground, Indian Hill West Prescott and Iron Springs.

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.

&&

LAT...LON 3464 11247 3451 11249 3451 11266 3464 11265
TIME...MOT...LOC 2120Z 102DEG 7KT 3458 11259

KD