257
FXUS65 KFGZ 181045
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
345 AM MST Mon Aug 18 2025

.SYNOPSIS...Isolated showers and thunderstorms will be possible
this afternoon over eastern Arizona, with hot and dry conditions
expected elsewhere. Monsoonal moisture looks to increase over the
coming days, with scattered to widespread storms expected by weeks
end. Otherwise, hot temperatures and light winds look to prevail.

&&

.DISCUSSION...Today...A decaying MCS over southeastern Arizona
will push moisture northward into central Arizona this morning,
likely just enough to get a few showers and thunderstorms going
this afternoon across the White Mountains. 00Z HREF and U of A WRF
guidance seem to favor this as well, although the U of A WRF does
hint at potentially some activity a bit further north into
central Apache County.

For the rest of northern Arizona, warm and dry conditions are
expected as high pressure begins to strengthen over Colorado and New
Mexico.

Tuesday onward...Heights continue to rise as the nearly 596/597 dam
ridge gradually strengthens and retrogrades through the week.
Monsoonal moisture does look to increase each day, with the high
setting up in a more favorable Four Corners high setup. Much of the
EPS, GEFS, and CMCE members seem to favor a notable increase in
PWATs through the remainder of the week, with the vast majority of
the members around 0.80-1.10 inches at KFLG by weeks end.

While the moisture looks to be there, the only limiting favor looks
to potentially be the strength of the ridge. Model soundings do show
a fairly strong subsidence inversion, especially initially, which
would limit the upscale growth potential of any storms that try to
develop. By the end of the week though, the ridge looks to weaken
some, which would help to allow for deeper convective development.
Thus, while activity does pick up the mid-week, the best chances look
to set in by near the end of the week and over the weekend.

With the rising heights, temperatures are expected to increase
through the middle of this week. Afternoon highs look to peak at
around 5-10F above normal, with temperatures in the 80s F across the
higher terrain and mid-90s F to mid-100s F in the lower elevations.
Portions of the Grand Canyon and lower elevations of Yavapai County
may flirt with or exceed 110F. For this reason, an Extreme Heat
Warning has been issued for the Grand Canyon below 4000 feet from
Tuesday and Wednesday. A watch follows for Thursday and Friday as
confidence in how much (or how little) of an affect the moisture
increase will have on temperatures is not high enough to support a
warning at this time.

&&

.AVIATION...Monday 18/12Z through Tuesday 19/12Z...VFR conditions.
ISO -SHRA/-TSRA expected 20Z-03Z, mainly near and east of a KSOW-
KRQE line. Winds W/SW 5-10 kts from 18Z-02Z, otherwise VRB. Gusty,
erratic winds possible in and around TS.

OUTLOOK...Tuesday 19/12Z through Thursday 21/12Z...VFR conditions.
ISO -SHRA/-TSRA possible each afternoon, mainly across the higher
terrain. Winds VRB 5-10 kts each day. Gusty, erratic winds possible
in and around TS.

&&

.FIRE WEATHER...Today and Tuesday...Hot and mainly dry conditions.
Isolated showers and thunderstorms over eastern Arizona this
afternoon, spreading to the Mogollon Rim on Tuesday. Winds southwest
5-15 mph each afternoon. Gusty and erratic winds possible in and
around thunderstorms. Minimum afternoon RH values 10-30%, highest
values across the White Mountains.

Wednesday through Friday...Hot temperatures continue, along with
increasing chances for showers and thunderstorms each day. Winds
primarily variable 5-10 mph. Gusty and erratic winds possible in and
around thunderstorms. Minimum afternoon RH values 10-30%, highest
values across the White Mountains and Mogollon Rim.

&&

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

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

&&

$$

PUBLIC...Humphreys
AVIATION...Humphreys
FIRE WEATHER...Humphreys

For Northern Arizona weather information visit
weather.gov/flagstaff