Flash Flood Warning 12, NWS Flagstaff, AZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
256 PM MST Fri Jul 28 2023

.SYNOPSIS...The monsoon looks to ramp up over the coming days with
increasing chances for afternoon and evening showers and
thunderstorms. Hot conditions will continue across the region
through the first half of the weekend before finally starting to
cool down as monsoon activity increases.

&&

.DISCUSSION...High pressure aloft remained centered over the
Arizona/New Mexico border during the afternoon. At the same time
an inverted trough was located over central Mexico. Over the
coming days these two features will interact leading to increasing
chances for showers and thunderstorms through at least Monday or
Tuesday.

For this afternoon and tonight...As expected, with a favorable
pattern in place, a large thunderstorm complex developed over
northwest Mexico Thursday night/Friday morning. The result has
been an ongoing surge of moisture into southern Arizona from the
Gulf of California. Yuma was carrying a 62 degree dew point with
southeast winds at 10 mph gusting to 20 mph during the afternoon.
Some of this moisture is sure to make it into portions of southern
Yavapai County by late this afternoon on the wings of our normal
southwest afternoon flow. The flow aloft today is more favorable
for storms that develop over the eastern Mogollon Rim and White
Mountains to move west to southwestward into the lower elevations.
Gusty outflow from this activity could collide with the Yavapai
County moisture for a better chance of severe thunderstorms and
flash flooding late this afternoon and into the evening.

For Saturday through Tuesday...The high pressure system looks to
shift northward toward the Four Corners then eastward toward
Oklahoma through this period with the Mexico inverted trough
moving closer to Arizona. The result will be a continued flow of
moisture into Arizona from over the Gulf of California with a
flow pattern aloft that favors more widespread and organized storm
activity. Storms during this period will likely move southward
off the Mogollon Rim into the low desert of central Arizona with a
heightened severe thunderstorm and flash flood threat.

Wednesday and beyond...Models show a stabilizing, capping
southwest flow developing across Arizona as the high center shifts
eastward with a downturn in monsoon activity expected.

&&

.AVIATION...For the 00Z TAF Package...Look for mainly VFR conditions
expected over the next 24 hours. Look for scattered showers and
thunderstorms through 03Z, mainly along/south of a KPGA-KINW-KRQE
line with isolated activity further north. Be on the lookout for
wind gusts of 35 to 45 knots in the vicinity of storms. Look for
another round of showers and thunderstorms on Saturday. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Saturday and Sunday...Scattered afternoon and evening
showers and thunderstorms on Saturday will become numerous on Sunday
across northern Arizona with the best chances along and south of the
Mogollon Rim through the White Mountains. The primary threats will
be lightning, erratic outflow winds of 35 to 45 mph, and rainfall
rates of 0.50-1.00" per hour in any storms. Activity will gradually
subside each evening.

Monday through Wednesday...Scattered to numerous showers and
thunderstorms are forecast each afternoon. Outside of any outflow
winds, expect west-southwest winds 10 to 20 mph each afternoon.
Daytime temperatures cooling through the period.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 8 PM MST Sunday for AZZ006.

&&

PUBLIC...McCollum
AVIATION...McCollum
FIRE WEATHER...McCollum

For Northern Arizona weather information visit
weather.gov/flagstaff

Preliminary Local Storm Report
National Weather Service Flagstaff AZ
1234 PM MST Fri Jul 28 2023

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

1150 AM     Hail             4 E Prescott Courthouse 34.55N 112.41W
07/28/2023  M0.88 inch       Yavapai            AZ   Public

            Nickel-size hail reported near the Prescott
            Gateway Mall.

&&

BAJ

Preliminary Local Storm Report
National Weather Service Flagstaff AZ
109 PM MST Fri Jul 28 2023

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

1100 AM     Hail             4 WSW Prescott Airport  34.62N 112.49W
07/28/2023  M0.75 inch       Yavapai            AZ   Public

            Penny-size hail reported 1 mile north of
            Pioneer Parkway at Williamson Valley Road.

&&

BAJ