Flash Flood in Arizona, August 2 to 3, 2018

Area Forecast Discussion
National Weather Service Flagstaff AZ
302 PM MST Thu Aug 2 2018

.SYNOPSIS...Expect afternoon and evening chances for showers and
thunderstorms through Friday. For the weekend, chances decrease as
a passing disturbance brings drier air across our area. Moisture
returns early next week with storm chances increasing across the
northland.

&&

.DISCUSSION...
Monsoonal moisture will continue to create a favorable environment
for widespread showers and thunderstorms through the afternoon and
evening hours today. Light steering flow will allow for slow
moving storms to create situations where flash flooding may occur
especially over flood prone locations.

Most of the stronger activity continues to be located in Yavapai
county this evening where skies clear significantly earlier in the
day than other locations along the rim. This allowed for increase
solar insolation and subsequent heating to occur.

Storm-top winds are pushing cloud tops generally off to the
northeast and creating additional shade, limiting further
widespread insolation and modifying the airmass across much of the
high country. This is helping further limit storm growth and
aligns well with with current lifted index values highest in
Yavapai County and dropping across much of the Mogollon Rim.

Storm activity should begin to decrease across the area around
sunset as diurnal heating shuts off.

A similar situation is expected again on Friday as daytime
heating initiates convection over the higher terrain with
expectations for the bulk of the shower activity to develop over
the rim and propagate across Yavapai and Gila counties.

A drying trend is expected to develop Saturday and Sunday as
zonal flow moves into the southern great basin and cuts down on
our available moisture. The decrease in available moisture will
result in convection being limited to the highest terrain such as
the White Mountain and San Fransisco Peaks. However by early next
week moisture should be increasing again as the zonal flow moves
back northward and the ridge redevelops allowing for moisture to
once again flow into northern Arizona from the Gulf of California.

&&

.AVIATION...For the 00Z package...Expect thunderstorms activity to
diminish this evening mainly after 02Z. Local IFR in +RA, erratic
wind gusts, and hail will be possible near any of the stronger
storm cells. Storm activity should begin to diminish after 02Z
Fri. Aviation discussion not updated for TAF amendments.
AdditionalShowers are expected to develop Friday around 18Z.

&&

.FIRE WEATHER...Areas from the Mogollon Rim southward will
continue to remain favored for afternoon and evening thunderstorms
again on Friday. Erratic outflow winds should be expected near
any thunderstorm activity. In addition, heavy rain and hail will
also be possible. Temperatures will remain above average. A
warming and drying trend is expected to develop on Saturday and
limit thunderstorm activity.

Sunday through Tuesday...The downward trend in thunderstorm
coverage will continue over the weekend. An increase in monsoonal
activity is possible on Monday and Tuesday as deeper moisture
returns to the region.

&&

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

&&

PUBLIC...Suk
AVIATION...Suk
FIRE WEATHER...Suk

For Northern Arizona weather information visit
weather.gov/flagstaff

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
256 PM MST THU AUG 2 2018

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

0245 PM     FLASH FLOOD      4 E PRESCOTT COURTHOUSE 34.55N 112.40W
08/02/2018                   YAVAPAI            AZ   TRAINED SPOTTER

            HEAVY RAIN CAUSING HIGH WATER (DEPTH
            UNKNOWN) ON HWY 69 AT LEE BLVD.

&&

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