Flash Flood Warning 84, NWS Flagstaff, AZ

740 
WGUS75 KFGZ 132326
FFSFGZ

Flash Flood Statement
National Weather Service Flagstaff AZ
426 PM MST SUN AUG 13 2017

AZC005-132331-
/O.EXP.KFGZ.FF.W.0084.000000T0000Z-170813T2330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Coconino-
426 PM MST SUN AUG 13 2017

...THE FLASH FLOOD WARNING FOR COCONINO COUNTY WILL EXPIRE AT 430 PM
MST...

At 420 PM MST, National Weather Service Doppler radar indicated that 
no rainfall was currently falling in Hualapai Canyon, which is the 
trail leading into Supai. Law enforcement officials in Supai report 
no flooding and the Flash Flood Warning for the Hualapai Canyon 
section will be allowed to expire at 430 PM MST.

Sections of the trail may still have running or pooled water, use 
caution. The Flash Flood Warning for Havasu Creek continues until 
545 PM MST.

LAT...LON 3623 11269 3616 11272 3614 11272 3607 11271
      3604 11272 3598 11273 3598 11277 3607 11273
      3616 11274

$$

Area Forecast Discussion
National Weather Service Flagstaff AZ
932 AM MST Sun Aug 13 2017

.SYNOPSIS...Expect scattered showers and thunderstorms this
afternoon and evening, with flash flooding and lightning being
the primary threats. Much drier air will bring a decreasing trend
in storm coverage by Monday, with isolated or no storms from
Tuesday through the remainder of the week.

&&

.UPDATE...Morning sounding showed mid to upper level drying
compared to yesterday morning. The available liquid (Pwat) is
just slightly less than yesterday morning (0.81 vs 0.87). There is
a somewhat stable layer between around 520 and 450 mb. Surface
heating will be able to overcome this by late morning. Forecast
was updated to cover two areas of ongoing convection over the
Black Mesa area and western Coconino County along the Colorado
River. Today will be the last active storm day for much of this
week.

&&

.PREV DISCUSSION /407 AM MST/...Overnight rain and thunderstorm
activity continues over far southern Yavapai County following a
very active evening, and is slowly shifting southward. Greater
shower and thunderstorm coverage exists over the Phoenix area and
on toward the south. This nocturnal convection is in association
with divergent flow aloft connected to a short wave trough moving
across southern Utah. Expect this rain activity to continue
weakening and moving toward the south and out of Yavapai County.

For today...scattered showers and thunderstorms are forecast to
develop around mid-day, mainly from the Mogollon Rim/Coconino
Plateau northeastward. It is likely that late evening and
overnight convective activity across Yavapai and northern Gila
counties has decreased instability in those areas. NAEFS mean
precipitable water values are somewhat lower today than they were
yesterday, but still around 1.00" along the Rim and a little
higher to the south. This is plenty of moisture to support a
flooding threat with the strongest storms. In addition, forecast
0-6 kilometer shear values are in the 15-25 kt range from the
west-northwest. This is enough to support some storm organization
and possible training of multiple storms over the same areas.
Combining all these factors together, the flash flood threat today
is lower than it was on Saturday, but still worth noting.

On Monday, flow aloft increases from the southwest as a strong
short wave trough begins to move toward Arizona from the Great
Basin. We expect to observe a few thunderstorms on Monday, but
coverage of storms should be less than what we have observed this
weekend as moisture values will be on the decrease. Wind gusts in
excess of 30 mph are forecast Monday afternoon on the Coconino and
Kaibab Plateaus.

The aforementioned Great Basin short wave trough is forecast to
move across northern Arizona on Tuesday. Another windy day is
forecast, with late morning/afternoon southwest wind gusts
possibly exceeding 30 mph over much of the region. This trough
will initiate a pronounced monsoon break which is forecast to last
for the remainder of the week. Seasonable temperatures, no
precipitation and afternoon southwest breezes are expected.

Ensemble models expect a gradual return of moisture toward the
very end of this week, or more likely the early part of next week.
Along with this moisture, shower and thunderstorm chances are
expected to return to northern Arizona. Until then, we expect a
fairly extended break in precipitation from Tuesday until at least
Friday, maybe Saturday.

&&

.AVIATION...For the 18Z package...Scattered showers and
thunderstorms will redevelop late this morning and continue into the
afternoon. Storm development will be most favored along the Mogollon
Rim and to the northeast. Localized MVFR/IFR conditions expected in
the stronger storms. Storm coverage and intensity will diminish
after 03Z Mon. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Scattered showers and thunderstorms will develop
again today with a decreasing trend in storm coverage beginning
Monday. Temperatures will remain slightly below normal.

Tuesday through Thursday...A drier air mass will move back into the
region with significantly decreased storm chances. Breezy
southwesterly winds will develop on Tuesday with lighter winds
Wednesday and Thursday.

&&

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

&&

PUBLIC...MAS/AT
AVIATION...KD
FIRE WEATHER...TM

For Northern Arizona weather information visit
weather.gov/flagstaff

Hazardous Weather Outlook
National Weather Service Flagstaff AZ
627 AM MST Sun Aug 13 2017

AZZ004>018-037>040-140200-
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-
627 AM MST Sun Aug 13 2017

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

.DAY ONE...Today and Tonight

Expect scattered showers and thunderstorms initiating around mid-
day, with the greatest coverage anticipated from the Mogollon Rim
and Coconino Plateau northeastward. Modest deep-layer wind shear
will support some storm organization. Atmospheric moisture has
decreased somewhat relative to yesterday, but west-northwest winds
could cause multiple storms to develop over the same areas,
yielding a flash flood threat. Thunderstorms today could produce
some hail in addition to cloud-to-ground lightning.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

Thunderstorm coverage will decrease on Monday, and wind speeds
will increase in response to the approach of a trough from the
Great Basin. Wind gusts in the 30-40 mph range are likely on
Monday afternoon along the Coconino and Kaibab Plateaus. The
trough will cross northern Arizona on Tuesday, bringing breezy
conditions and significant drying to the region. A break from
thunderstorms and precipitation is currently expected from
Tuesday through at least Friday, and likely for most of the area
through Saturday. Moisture is expected to gradually increase early
next week.

.SPOTTER INFORMATION STATEMENT...

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