735
FXUS65 KFGZ 192313
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
413 PM MST Tue Aug 19 2025

.SYNOPSIS...Isolated showers and thunderstorms will continue into
this evening in eastern Arizona, with hot and dry conditions
expected elsewhere. Monsoonal moisture looks to increase over the
coming days. Scattered to widespread storms, some with heavy rain
and localized flash flooding, are expected to develop by weeks
end and continue into early next week.

&&

.DISCUSSION...Strong high pressure (500 mb heights 596-598 dam) is
forecast to be centered near the four corners through Friday
before gradually weakening and sliding southward into New Mexico
later this weekend/early next week. This will be a much more
favorable setup for transporting monsoon moisture into our region
than we have seen lately, and should set the stage for an active
period of showers and thunderstorms. With such a strong high
pressure system, heat will also be an issue through at least
Thursday or Friday. An Extreme Heat Warning is in effect through
Wednesday for the lower elevations of Grand Canyon, with a watch
for Thursday/Friday. We left the watch as is for now, as
increasing clouds and precip chances could keep temperatures below
warning thresholds. The lower elevations of Yavapai County will
also be quite hot through Friday (Verde Valley near 105F), though
the same issues with cloud cover/precip may impact these areas
each day by early/mid afternoon and keep temperatures down a bit.
For today, the main area of moisture increase has been far eastern
Arizona, with isolated/scattered showers and thunderstorms in the
White Mtns, Chuska Mtns, and around Black Mesa. CAMS suggested
that some of these storms near the White Mountains into eastern
Gila County could become strong later this afternoon/evening and
push an outflow boundary westward.

Wednesday - a continued westward push of moisture is forecast as
the large scale flow as well as outflow boundaries are favorable
for moistening up areas as far west as Flagstaff and at least the
eastern half of Yavapai County. Storm chances go up to 30-60%
along the Mogollon Rim to 20-30% in eastern Yavapai. By Thursday,
higher storm chances push even farther west and north, with 20-40%
chances all the way to the UT/AZ line.

Friday into early next week - shower and thunderstorm coverage is
forecast to remain high (50-80%) each day with some fluctuation
related to outflows and debris cloudiness though these are not
really predictable more than 24 hours out. With elevated precipitable
water values across the region, the threat of locally heavy rain
and flash flooding will increase. In addition, easterly steering
flow Fri/Sat will be favorable for pushing storms off the high
terrain westward into Yavapai County where moisture and
instability will be highest each afternoon. This pattern can
produce strong to locally severe thunderstorms with strong winds
and hail in this area. As the high gradually weakens and shifts
southward, high temperatures should fall back closer to normal by
the weekend and early next week.

&&

.AVIATION...Wednesday 20/00Z through Thursday 21/00Z...VFR
conditions expected to persist through the TAF period. Isolated
-SHRA possible through 06Z primarily across Apache and Navajo
 Counties. Light and variable winds expected through 18Z, before
 winds increase to ~ 10kts but remain variable in direction.
 Additional SHRA/TSRA possible after 18Z along and east of a KPRC-
 KPGA line.

OUTLOOK...Thursday 21/00Z through Saturday 23/00Z...VFR conditions
will persist outside MVFR conditions in heavier SHRA/TSRA. Daily
chances for showers/storms possible between 18Z-03Z, with greatest
activity likely across the higher terrain. Outside of storm
driven gusty winds, look for variable winds 5-15 kts.

&&

.FIRE WEATHER...Wednesday and Thursday...Hot and mainly dry
conditions continue. Isolated to scattered showers and thunderstorms
expected Wednesday, most numerous across eastern AZ. More widespread
showers and thunderstorms expected on Thursday. Winds generally
variable 5-10 mph. Gusty and erratic winds possible in and around
thunderstorms. Minimum afternoon RH values 10-30%, highest across
the White Mountains.

Friday through Sunday...Good chances (60-80%) for showers and
thunderstorms each day. Winds will primarily be variable 5-10 mph.
Gusty and erratic winds possible in and around thunderstorms.
Minimum afternoon RH values 10-30%, greatest over the high
terrain.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...
Extreme Heat Warning until 8 PM MST Wednesday for AZZ006.

Extreme Heat Watch from Wednesday evening through Friday evening
for AZZ006.

&&

$$

PUBLIC...JJ
AVIATION...Konieczny
FIRE WEATHER...BAK

For Northern Arizona weather information visit
weather.gov/flagstaff