Flash Flood Warning 46, NWS Flagstaff, AZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
1121 AM 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...Monday 20/18Z through Tuesday 21/18Z...Scattered to
numerous SHRA/TSRA developing early this afternoon. KPGA likely
stays dry through 05Z. Stronger storms will be capable of
producing wind gusts 30-45 kts, hail, and brief MVFR and IFR
conditions. Storms may continue well into the overnight period
with heavy rain becoming the main threat. Outside of storms, winds
light and variable.

OUTLOOK...Tuesday 21/18Z through Thursday 23/18Z...Look for
SHRA/TSRA activity through the period, most numerous during the
afternoon/evening hours. Stronger storms will produce brief MVFR
and IFR conditions and gusty winds to 30-40 kts. Localized IFR
conditions due to low clouds and fog possible during the overnight
hours. Outside of storms, surface winds light and variable.

&&

.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...None.

&&

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

For Northern Arizona weather information visit
weather.gov/flagstaff

Special Weather Statement
National Weather Service Flagstaff AZ
1221 PM MST Mon Jul 20 2026

AZZ015-201945-
Western Mogollon Rim AZ-
1221 PM MST Mon Jul 20 2026

...A STRONG THUNDERSTORM WILL IMPACT COCONINO COUNTY UNTIL 1245 PM
MST...

At 1221 PM MST, Doppler radar was tracking a strong thunderstorm over
A1 Mountain, or 6 miles northwest of Flagstaff, moving southwest at
10 mph.

HAZARD...Wind gusts up to 40 mph and nickel size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
  Fort Valley, Bellemont, A1 Mountain, Wing Mountain, A One Lake and
  Riordan.

This includes the following highways...
Interstate 40 between mile markers 184 and 191. Highway 180 between
mile markers 220 and 229.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Monitor the weather situation closely and be alert for threatening
weather conditions.

&&

LAT...LON 3534 11177 3528 11165 3518 11174 3527 11189
TIME...MOT...LOC 1921Z 45DEG 9KT 3526 11173

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...40 MPH

Zanker