Flash Flooding in Arizona, August 27, 2022

Area Forecast Discussion
National Weather Service Flagstaff AZ
902 AM MST Sat Aug 27 2022

.SYNOPSIS...Widespread showers and storms are forecast for today,
making flash flooding possible in vulnerable areas. Scattered
storms persist Sunday before drier conditions begin to develop
for the start of the week. With this drier air in place, daytime
highs will heat up to above normal much of next week.

&&

.UPDATE...Skies are sunny to start the day across northern and
central Arizona. Low level moisture remains plentiful with surface
dewpoints in the 50s to low 60s for the entire forecast area.
Instability will be highest along/south of the Mogollon Rim, with
mean MUCAPE from HREF at 1000-1500 J/kg in Yavapai County this
afternoon. General storm motion toward the east at 10-15 mph with
light low level flow. A few strong or possibly severe pulse storms
are likely this afternoon, with flash flooding also a risk
especially for vulnerable areas such as burn scars. Updated
today's rain chances to show an increase in northeast AZ,
otherwise the current forecast looks good.

&&

.PREV DISCUSSION /235 AM MST/...Widespread monsoonal thunderstorm
activity is expected today, especially from Greater Flagstaff to
the White Mountains and points south. Clear skies in many spots
could allow for an early start to convection, as the sun gets to
work in the morning, injecting instability into the atmosphere.
Overall, storms will move generally eastward, giving the Painted
Desert and Navajo Nation more chances for storms as the day
progresses. If storms train over vulnerable locations, flash
flooding could become a concern.

A significant shift in the pattern next week will result in
widespread hotter and drier conditions. The incoming intrusion of
dry air due to a swift northwesterly flow will inhibit monsoonal
activity for most, except for the White Mountains.

However, much uncertainty exists over the days heading into this
drier period. While the upper level flow looks increasingly less
conducive for storms day-after-day, robust instability from steep
lapse rates and moisture near the surface could provide the
catalyst for isolated strong thunderstorms.

Toward the end of next week, moisture looks poised to return to
northern Arizona, bringing higher storm chances along with it. But
the placement of the Southwest High will largely determine the
strength of this monsoonal pattern's return. The specifics of this
synoptic setup are still unclear.

&&

AVIATION...For the 18Z TAF package...Scattered showers and
thunderstorms developing over higher elevations around mid day,
spreading slowly eastward through the mid afternoon to early
evening. Localized/brief MVFR in storms. Highest coverage KFLG-KSJN
southward. Showers and storms diminishing after 03Z. Gusty winds in
the vicinity of storms. Otherwise, light winds and VFR conditions
away from storms. Aviation discussion not updated for TAF amendments.

&&

FIRE WEATHER...Look for scattered showers and thunderstorms
today with decreased activity on Sunday. Lightning, flash flooding,
and outflow winds will be the main threats.

Monday through Wednesday...Warmer and drier with only a slight
chance of thunderstorms.

&&

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

&&

PUBLIC...JJ/BAJ
AVIATION...JJ
FIRE WEATHER...McCollum

For Northern Arizona weather information visit
weather.gov/flagstaff