733
FXUS65 KFGZ 210836
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
136 AM MST Fri Jun 21 2024

.SYNOPSIS...Daily chances for showers and thunderstorms are
forecast through the weekend and into the middle of next week,
along with warming temperatures.

&&

.DISCUSSION...Today...The remnants of Tropical Storm Albert
continue to pump moisture northward into Arizona. While at the
same time, a trough over the Great Basin begins to lift into the
Northern Rockies today and high pressure builds into the southwest
from the east.

00 UTC HREF guidance has around 800-1200 J/Kg of surface-based CAPE
over much of the area, with the highest amounts most likely near the
AZ/UT border. Given the influence of the trough, 0-6km bulk shear
looks to increase today, with 35-45 kts expected near the AZ/UT border.
This added shear and instability will allow for more organized
thunderstorms this afternoon, with a few strong to severe storms
capable of producing damaging winds and hail likely. Elsewhere,
shear begins to weaken rapidly, with generally 20 kts expected,
favoring less organized thunderstorms across the rest of the
region.

Given PWATs in the 0.80-1.20 inch range, heavy rainfall will be
possible and could lead to areas of localized flash flooding.
However, given storm motions of around 25-30 kts, the residency time
of any one storm will be limited. Therefor, the flash flood threat
is largely limited to any flood sensitive areas (slot canyons,
recent burn scars, and urban areas) or locations where training
thunderstorms occur. HREF PMM guidance shows the greatest risk for
heavy rainfall will mainly be across far northern Arizona into the
Four Corners region, where better forcing looks to be available.

All and all, the greatest chances for showers and thunderstorms this
afternoon and evening will be north of a Grand Canyon to St. Johns
line. More isolated coverage is expected across the Mogollon Rim.

Saturday and Sunday...After the trough lifts, high pressure will
continue to build eastward into Arizona. Moisture remains trapped
under the ridge, so daily chances for showers and thunderstorms will
continue. However with weaker forcing in place, less organized
thunderstorm activity is expected. While at the same time, the
threat for flash flooding increased with slower storm motions and
increased moisture. Coverage areas also look to shift to the higher
terrain, where given the lack of synoptic forcing, orographic
forcing will aid convective initiation.

Monday through Thursday...Heights continue to rise into next week as
high pressure becomes centered over Arizona and New Mexico. Moisture
remains in place, so chances for showers and thunderstorms will
remain in the forecast. However, coverage will begin to wain each
day into next week. Temperatures look to rise, with the potential
for excessive heat across the lower elevations by the middle of next
week.

&&

.AVIATION...Friday 21/06Z through Saturday 22/06Z...Only a few
isolated showers expected overnight, with generally southerly
winds decreasing to 5-15 mph most areas. Storms will develop
again on Friday, with scattered to numerous storms along and near
the Utah border after 18Z, with MVFR and local IFR conditions.
Expect south to southwest winds on Friday 20-30kts, and gusty
around thunderstorms.

OUTLOOK...Saturday 22/06Z through Monday 24/06Z...Showers and
thunderstorms will develop again on Saturday and Sunday (30-60%
chance) with MVFR and local IFR conditions in the stronger
storms.

&&

.FIRE WEATHER...Today and Saturday...Scattered to widespread showers
and thunderstorms each afternoon with showers continuing overnight.
Wetting rains are likely with any storms along with gusty and
erratic outflow winds up to 45 mph. Outside of outflow winds, south
to southwest winds at 25-35 mph today with lighter winds at 10-15
mph Saturday.

Sunday through Tuesday...Chances for showers and thunderstorms
continues through Monday, mainly along and south of the Mogollon Rim
and the White Mountains. Isolated to scattered activity on Tuesday,
mainly along the higher terrain. Temperatures remain seasonal with
light southwesterly flow around 10-15 mph each afternoon.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...None.

&&

$$

PUBLIC...Humphreys
AVIATION...BAK
FIRE WEATHER...Meola

For Northern Arizona weather information visit
weather.gov/flagstaff