Flash Flood Warning 24, NWS Flagstaff, AZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
955 AM MST Tue Jul 18 2017

.SYNOPSIS...Expect numerous showers and thunderstorms across
northern and central Arizona through mid-week. Heavy rainfall
rates from the stronger storms will be capable of producing flash
flooding. The threat for heavy rainfall and flash flooding will
continue through mid-week.

&&

.DISCUSSION...Updated forecast to delay the onset of
significant storm activity until after 18Z. Will be looking at the
possibility of the formation/location of an MCS this evening and
overnight. Will adjust POPS accordingly this afternoon. HRRR has the
development over Yavapai Country. NAM has the development more over
northwest Coconino County. Either way, it looks like an active night
tonight.

&&

.PREV DISCUSSION /331 AM MST/...The active monsoon continues for
northern Arizona today as widespread abundant moisture will combine
with an upper level disturbance making its way westward out of New
Mexico and into northeast Arizona.

This will lead to enhanced coverage and strength for storms near
the vorticity maximum Tuesday afternoon and overnight into
Wednesday. This westward progression should allow storms to
organize increasing the potential for rainfall rates in excess of
1 to 2 inches per hour lasting for an extended period of time.

Generally storms are expected to decrease around sunset and into
the evening hours, unfortunately this upper level disturbance is
expected to create an organizing mechanism that will allow for
showers and thunderstorms to continue to develop and propagate to
the west as Tuesday night gives way to Wednesday morning.

While models have some timing and location differences concerning
the actual placement of this event all operation models are
leaning towards this solution; with the higher resolution models
concurring that a mesoscale convective system is anticipated to
develop and move across the high country in the overnight hours.

As this system exits northwestern Arizona on wednesday another
round of convection will fire off of the higher terrain with local
storms in a favorable position to overwhelm drainages stressed
from the previously days' events.

On Thursday a slight decrease in moisture aloft is expected to
move into the area allowing for a slightly less active day for
convective thunderstorm development. Some storms are still
expected to form, however they should be more widely scatter than
their counterparts from the previous few days.

This respite will not last long with models suggesting that a
reinforcing surge of moisture will move back into the area from
the New Mexico border Friday and lasting into next week.

&&

.AVIATION...For the 18Z package...Numerous TSRA will develop across
northern Arizona this afternoon and continue through the evening
hours. Expect areas of MVFR with isolated IFR in +RA. A few storms
may produce severe wind and hail mostly south and west of a KGCN to
KSOW line. Expect conditions to improve from east to west aft 07Z
Wed. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Active monsoon conditions will continue with
scattered to numerous showers and storms each day. Convective
activity should continue overnight tonight as an upper level
disturbance moves into Arizona from New Mexico. The threat for heavy
rain will spread across all of Arizona through midweek.
Expect near average temperatures.

Thursday through Saturday...A brief decrease in storm coverage is
possible Thursday afternoon, with otherwise typical monsoon
conditions expected to continue.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...Flash Flood Watch from 11 AM MST this
morning through Wednesday evening FOR AZZ004>018-037>040.

&&

PUBLIC...MAS/SUK
AVIATION...MCT
FIRE WEATHER...DL

For Northern Arizona weather information visit
weather.gov/flagstaff

Hazardous Weather Outlook
National Weather Service Flagstaff AZ
331 AM MST Tue Jul 18 2017

AZZ004>018-037>040-190415-
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-
331 AM MST Tue Jul 18 2017

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

.DAY ONE...Today and Tonight

A flash flood watch is in effect for northern Arizona this
afternoon through Wednesday evening. Showers and thunderstorms
will develop off the higher terrain this afternoon and evening
before moving across the surrounding area. Showers and
thunderstorms are expected to continue overnight across northern
arizona.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

The flash flood watch will continue into Wednesday evening.
Models suggest a slight drying trend could be possible by later
this week depending on the movement of the high pressure ridge aloft.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is no anticipated at this time.

Special Weather Statement
National Weather Service Flagstaff AZ
1206 PM MST TUE JUL 18 2017

AZZ008-037-181930-
Yavapai County Valleys and Basins-Yavapai County  Mountains-
1206 PM MST TUE JUL 18 2017

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

At 1205 PM MST, Doppler radar was tracking a strong thunderstorm
near Groom Creek Subdivision, or 10 miles south of Prescott Valley.
This storm was moving west around 5 mph.

Dime size hail and winds in excess of 30 mph will be possible with
this storm.

Locations impacted include...
Ponderosa Park, Groom Creek Subdivision, Lower Wolf Creek Campground
and Upper Wolf Creek Group 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.

&&

LAT...LON 3446 11238 3438 11243 3440 11260 3451 11253
TIME...MOT...LOC 1905Z 115DEG 4KT 3443 11244

JJ

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
1211 PM MST TUE JUL 18 2017

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

0230 PM     TSTM WND DMG     6 WNW CHINO VALLEY      34.80N 112.55W
07/17/2017                   YAVAPAI            AZ   PUBLIC

            APPROXIMATELY 230 PM MONDAY, STRONG WINDS
            TORE A 24'X72' METAL ROOF FROM A SHED. BASED
            ON A PHOTO OF THE DAMAGE, WINDS ESTIMATED AT
            ABOUT 50-55 MPH. "IT TORE THE [METAL] SHEETS
            LIKE PAPER, AND SPLIT AND BROKE THE 2X6S".

&&

DLB