022
FXUS65 KFGZ 202354
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
454 PM MST Mon Jul 20 2026

.SYNOPSIS...Deep monsoonal moisture will remain over the area
through at least mid week, with a slight decrease later in the
week. With this moisture comes the daily threat of thunderstorms,
along with the risk for locally heavy rainfall and flooding. Daytime
temperatures will remain at or below normal much of the week, with
hotter temperatures possible toward the weekend.

&&

.DISCUSSION...An active monsoon pattern is forecast to remain in
place across northern Arizona for the next several days as a
ridge of high pressure centered over Colorado continues to pump
deep sub-tropical moisture into the region. Precipitable water
(PW) values are exceptionally high for mid-July, with guidance
showing an inch or more across northern Arizona, surface dew
points in the 50s at higher elevations, and dew points in the 60s
at lower elevations.

High-resolution model guidance indicates unusually high
instability today, with CAPE values, a measure of atmospheric
instability, ranging from 1000 to 2500 J/kg across the area. The
highest instability is concentrated along and south of the
Mogollon Rim. Coincident with the areas of highest instability,
pockets of 0-6km wind shear between 20 and 30 knots are forecast.
These shear values are higher than typically observed in mid-
July, and is expected to enhance storm organization and the severe
weather threat. As a result, we will be monitoring for flash
flooding alongside a moderate risk for powerful storms capable of
producing large hail and damaging wind gusts. Convective
development is expected to increase over the higher terrain
around noon before storms drift westward at 5-10 mph.

The monsoon high pressure cell is forecast to remain relatively
stationary over the next few days, ensuring that deep moisture
stays locked in place across northern Arizona. On Tuesday, an
inverted trough will move along the western side of the ridge and
track across Arizona, passing overhead on Wednesday. This feature
may provide additional dynamical lift to aid convective
development.

From Thursday onward, a shift in the synoptic pattern is
anticipated as the majority of model guidance shows the monsoon
high pressure cell strengthening and migrating westward. This
retrograding position will bring warming aloft, resulting in more
stable conditions. Under this scenario, we would see a downward
trend in storm activity and a gradual warming trend through the
end of the week. However, this shift will not bring a complete
shutdown in monsoon activity. The extended forecast maintains
probability of precipitation values of 30-50% over the higher
terrain, and 30% or less for the lower elevations.

&&

.AVIATION...Tuesday 21/00Z through Wednesday 22/00Z...Scattered
to numerous SHRA/TSRA will continue through 06Z. KPGA has
remained dry and will continue to stay dry through 05Z. Stronger
storms this evening will be capable of producing wind gusts 30-45
kt, hail, and brief MVFR and IFR conditions. After 06Z, activity
becoming isolated to low-end scattered. Localized IFR conditions
due to low clouds and fog are possible during the overnight hours.
Outside of storms, winds light and variable. Another active day
is expected of monsoon storms is expected Tuesday. Expect
scattered to numerous SHRA/TSRA with isolated +TSRA from late
Tuesday morning (~17Z) through the afternoon hours (~00Z). The
primary threat will be MVFR to IFR conditions in heavy rain. Gusty
outflow winds up to 45 kts and hail are also possible.

OUTLOOK...Wednesday 22/00Z through Friday 24/00Z...Expect
scattered to numerous SHRA/TSRA and isolated +TSRA Through
Wednesday, then as monsoon moisture decreases SHRA/TSRA coverage
will become scattered, but will continue to develop during the
late morning through late afternoon hours Thursday and Friday. Any
stronger storms will produce brief MVFR to IFR conditions. Some
IFR low clouds and fog possible, mainly for overnight hours.
Outside of storms, expect light winds around 5-10 kts.

&&

.FIRE WEATHER...Today and Tuesday...A medium to high grade
monsoon environment continues, with generally light winds outside of
outflow and thunderstorm activity. Most storms will produce wetting
rain and any stronger storms may produce flash flooding and hail,
especially through Tuesday evening.

Thursday through Saturday...Chances for showers and thunderstorms
continue, though coverage will decrease somewhat. Generally light
winds outside of outflow and thunderstorm activity. Most storms will
produce wetting rain and any stronger storms may produce localized
flash flooding. Expect a warming trend and minimum RH back to around
20% for the lowest elevations.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...
Flood Watch from Tuesday morning through Tuesday evening for
AZZ004>009-012>018-039-040.

&&

$$

PUBLIC...RR
AVIATION...Schank
FIRE WEATHER...Zanker

For Northern Arizona weather information visit
weather.gov/flagstaff