140
FXUS65 KFGZ 180513
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
1013 PM MST Mon Aug 17 2026

.SYNOPSIS...Temperatures warm up to 5 degrees above average
throughout the week. Low grade monsoon conditions continue with
only isolated storms for the first part of the week. By midweek,
thunderstorm coverage begins to increase across the area as more
moisture is drawn into the state.

&&

.DISCUSSION...High pressure across the region will result in
warming temperatures early this week and minimal monsoon
thunderstorm activity. Increasing moisture later this week will
bring increasing chances for showers and thunderstorms.

High pressure centered across the southwestern U.S. will remain
entrenched over the region through the week. Slight amplification
and minimal monsoon moisture will allow for warming temperatures
and potential heat related headlines yet again. Confidence is
increasing that we will reach heat warning temperatures for the
inner Grand Canyon (110F). The focus for thunderstorm activity
early this week will be over the White Mountains, where the
greater moisture resides. An isolated shower or storm is possible
as far west as the Flagstaff and the Yavapai county mountains. By
midweek, the high pressure ridge axis shifts toward the four
corners, while a tropical disturbance is forecast to move
northwestward across the southern Baja. Both of these will help to
initiate the northward push of moisture across Arizona. Expect
increasing moisture and thunderstorm chances from Wednesday
onward. It looks like we will return to at least a moderate
monsoonal pattern for the end of this week into next weekend.

Subsequently, the increase in moisture and rain chances will help
decrease temperatures later this week making heat less of a
concern. The potential for heavy rain and flash flooding will be
on the rise late this week perhaps lasting into the weekend.

&&

.AVIATION...Tuesday 18/06Z through Wednesday 19/06Z...Mainly VFR
conditions, with brief MVFR possible near showers/storms from 18Z
to 03Z. Scattered showers/thunderstorms in the White Mountains,
with isolated showers/storms over the Rim. Light and variable or
terrain driven overnight through 18Z, then by SW-W 5-10kt 18Z to
03Z, and returning to light and variable or terrain driven after
03Z. Gusty and erratic winds possible near storms.

OUTLOOK...Wednesday 19/06Z through Friday 21/06Z...VFR conditions,
with brief MVFR to IFR near showers/storms. Chance of isolated to
scattered storms over the Rim and White Mountains between
18Z-03Z, potentially becoming scattered to numerous by Friday.
Winds SW-W 5-15kts daytime, light and variable or terrain driven
overnight. Gusty and erratic winds possible near storms.

&&

.FIRE WEATHER...Tuesday and Wednesday...Temperatures 5 degrees above
average with isolated to scattered showers and thunderstorms each
day, best coverage over the eastern Mogollon Rim and White
Mountains. Winds SW-W 5-10 mph each day, gusty and erratic winds
possible near storms. Minimum RH values 15% lower deserts to 35% in
the White Mountains.

Thursday through Saturday...Temperatures continue to be about 5
degrees above average. Scattered showers and thunderstorms over the
Mogollon Rim and White Mountains with coverage increasing and
spreading westward compared to Wednesday. Winds SW-W 5-10 mph each
day, gusty and erratic winds possible near storms.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...
Extreme Heat Warning from 10 AM Tuesday to 8 PM MST Thursday for
AZZ006.

&&

$$

PUBLIC...MCT
AVIATION...Schank
FIRE WEATHER...Zanker

For Northern Arizona weather information visit
weather.gov/flagstaff