Areal Flood Advisory 21, NWS Flagstaff, AZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
936 PM MST Tue Jul 18 2017

.SYNOPSIS...Deep moisture and an area of low pressure over
western Texas moving west will bring numerous showers and
thunderstorms to northern and central Arizona through mid-week.
Heavy rainfall from the stronger storms will be capable of
producing flash flooding at least through Wednesday evening.

&&

.DISCUSSION...Ongoing convection with embedded strong storms and
heavy rain continuing over the CWA this evening. Mesoanalysis
suggests that mixed layer CAPE has come down significantly over
the past couple hours (down to 500-1000 now), and this is
reflected in the decrease in overall intensity of the storms.
Embedded cores, however, are still producing heavy rain. Observed
rainfall rates (some much greater than radar est) suggest
tropical drop distributions, consistent with this very moist
airmass. Anticipate that convection will slowly decrease later
this evening, with scattered to numerous storms continuing through
the night primarily over the western part of the CWA (aided by
the easterly wave working across the state). Have updated the
grids to reflect current and forecast precip trends.

&&

.PREV DISCUSSION /325 PM MST/...Very moist atmosphere and
approaching easterly waves have produced numerous showers and
thunderstorms across northern Arizona this afternoon. Heavy to
very heavy rain and over an inch diameter hail has been observed
(via radar). Very active afternoon!

Deep moisture will remain over the area through Wednesday evening.
The easterly flow across Texas and New Mexico will continue to
bring instability over Arizona. Both the HRRR and NAM show the
development of an MCS over Yavapai County or northwestern
Coconino County tonight into Wednesday.

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.
Current Flash Flood Watch is out through Wednesday evening to
cover this activity.

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 06Z package...Widespread SHRA/TSRA and MVFR
conditions will continue this evening...with coverage decreasing
after 08Z. Another active day is expected on Wed with storms again
increasing in coverage after 17Z on Wednesday, most numerous
along and north of the Mogollon Rim with isolated IFR in +RA.
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 through northern Arizona. The threat for heavy
rain will continue across all of Arizona through midweek. Expect
near average temperatures.

Friday through Sunday....An active monsoon pattern will continue
with daily chances for rain showers and thunderstorms. No
significant changes in the weather pattern are anticipated.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...Flash Flood Watch through Wednesday
evening FOR AZZ004>018- 037>040.

&&

PUBLIC...BAK
AVIATION...ET/BAK
FIRE WX...BAK

For Northern Arizona weather information visit
weather.gov/flagstaff

Hazardous Weather Outlook
National Weather Service Flagstaff AZ
133 PM MST Tue Jul 18 2017

AZZ004>018-037>040-190430-
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-
133 PM MST Tue Jul 18 2017

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

.DAY ONE...This Afternoon and Tonight

A flash flood watch is in effect for northern Arizona this
afternoon through Wednesday evening. Showers and thunderstorms
will develop and generally move westward. 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.

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

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

0600 PM     FLASH FLOOD      2 SSE DEWEY-HUMBOLDT    34.50N 112.23W
07/18/2017                   YAVAPAI            AZ   COUNTY OFFICIAL

            RAPID 4 FOOT RISE ON AGUA FRIA RIVER AT
            HUMBOLDT.

&&

JJ

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

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

0915 PM     FLASH FLOOD      1 SSE SLIDE ROCK        34.94N 111.75W
07/18/2017                   COCONINO           AZ   LAW ENFORCEMENT

            LAW ENFORCEMENT REPORTS BOULDERS ON 89A.
            WATER DEPTH UNKNOWN. SPOTTER REPORTS FLOODED
            ROADWAYS 89A AND DRY CREEK RD 6-8 IN
            ESTIMATED IN ROAD.

&&

ET

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

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

0624 PM     HAIL             TAYLOR                  34.45N 110.11W
07/18/2017  E0.75 INCH       NAVAJO             AZ   TRAINED SPOTTER

            SPOTTER REPORTS PENNY SIZE HAIL 0.75" IN
            TAYLOR.

&&

ET