842
FXUS65 KFGZ 310522
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
1022 PM MST Sun Aug 30 2026

.SYNOPSIS...Active monsoon pattern will continue through Monday,
with flash flooding being a primary concern. Drier and slightly
warmer conditions then set in but the middle of the week, before
precipitation chances potentially return to close out the week.

&&

.DISCUSSION...This afternoon...Another round of showers and
thunderstorms are expected across central and northern Arizona
today. Storms have already initiated this morning across central
Arizona, though activity remains fairly mundane. Coverage is
expected to increase gradually through the rest of the afternoon,
especially north and east of the Mogollon Rim.

Latest RAP guidance has slightly lower MLCAPE values today, but
remain around 500 J/Kg across the Four Corners, increasing along a
northeast to southwest gradient, to around 1500 J/Kg across Yavapai
County. 0-6 km wind shear looks to remain around 20-30 kts from the
trough over the west, however this looks to be decreasing through
the day. Therefore, a couple strong to severe thunderstorms look to
remain a possibility this afternoon, with damaging winds and large
hail the main threats.

PWATs look slightly lower this morning based on the latest RAP
analysis, however, guidance forecasts these values to increase
through the afternoon. PWATs are expected to range from around an
inch across the northeast to around 1.5 inches south of the Mogollon
Rim. This will lead to very high rainfall rates with any stronger
storm, which combined with already saturated soils will lead to an
enhanced flash flood potential today.

Tonight...Much of the hi-res guidance continues to forecast a
complex of storms to move northward out of the Lower Deserts later
this evening and overnight. As the MCS moves northward, widespread
thunderstorms look to continue through the overnight across much of
northern Arizona. 12Z HREF PMM guidance has a 30-50% chance of
exceeding 1" in 3 hours with this system across much of Yavapai and
Gila counties overnight, and potentially expending a bit further
northward into Coconino. The HREF also highlights a 10% probability
for exceeding 3" in 3 hours.

The widespread nature of the coverage and the already saturated
soils in some areas will only further enhance the risk. Therefore, an
elevated risk of flash flooding looks to remain into the overnight
hours across much of central and potions of northern Arizona. A
Flash Flood Watch is in effect starting this afternoon and lasting
through Monday night.

Monday...One last day of active monsoonal conditions looks to
continue into Monday. Coverage looks to increase as a shortwave
moves through the area from the west, adding upper-level dynamics to
aid in precipitation development. However, some uncertainty does
remain given the potential for debris clouds from overnight
convection. This could potentially result in delayed convective
initiation and/or reduced coverage. Nevertheless, the flash flood
threat remains, along with potentially a couple strong to severe
thunderstorms.

Tuesday through Saturday...A fast-moving trough looks to move
through Great Basin near the middle of next week. This looks to
initially suppress monsoonal moisture further south, with much of
the GEFS, EPS, and CMCE member showing a sharp decline in PWATs for
the middle of next week. Operational guidance seems to have trended
further westward with Hurricane Karina, thereby limiting the
northward push of the sub-tropical moisture surge along Baja
California.

However, with another tropical system potentially developing behind
Karina and troughing remaining over the west, an increase in
moisture later in the week remains a possibility. GEFS, EPS, and
CMCE members remain split on continuing with the downward trend, or
increasing PWATs potentially as early as Thursday/Friday. Therefore,
uncertainty remains high near the end of the forecast package as the
exact timing and track of the both the trough and potential tropical
cyclone are crucial.

The operational guidance does have heights tick upwards slightly, so
a slight warming trend seems likely, but overall we look to remain
seasonable to slightly cooler than normal temperature wise into next
week.

&&

.AVIATION...Monday 31/06Z through Tuesday 01/06Z...Mainly VFR
conditions outside of localized MVFR/IFR in heavier precipitation.
Scattered to numerous SHRA/TSRA expected to continue at times
through the cycle. Gusty/erratic winds likely near storms,
otherwise W-SW winds 10-20 kts daytime, light/variable overnight.

OUTLOOK...Tuesday 01/06Z through Thursday 03/06Z...Expect
improving conditions with periods of few clouds and only isolated -SHRA/-TSRA.
Gusty/erratic winds likely near storms, with SW winds 10-20 kts
during the afternoon hours and becoming light and variable
overnight.

&&

.FIRE WEATHER...This afternoon through Tuesday...Active monsoonal
weather continues through Monday evening, including the overnight
hours. Storms will be capable of producing hail, heavy rain,
frequent lightning, and gusty/erratic winds. A Flash Flood Watch is
in effect for all of central/northern AZ this afternoon through
Monday night. A cooling trend is expected, leaving daytime highs 5-
10 degrees below normal by Monday. Outside of storm driven outflows,
look for southwest winds 10-20 mph this afternoon, then 5-15 mph
Monday and Tuesday.

Wednesday through Friday...Precipitation chances decline through the
middle of the week, with only isolated storms across the higher
terrain through Thursday. An increase in storm activity is possible
by Friday. Daytime highs will be close to seasonal norms. Look for
southwest winds 10-20 mph each afternoon, becoming light and
variable overnight.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Monday evening for AZZ004>018-037>040.

&&

$$

PUBLIC...Humphreys
AVIATION...Zanker
FIRE WEATHER...JJ

For Northern Arizona weather information visit
weather.gov/flagstaff