877
FXUS65 KFGZ 182028
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
128 PM 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 developing by
weeks end. Otherwise, hot temperatures and light winds look to
prevail.

&&

.DISCUSSION...High pressure, currently centered over the New
Mexico/Colorado border, will slowly build westward over the
coming days becoming centered over the southwest United States.
There is no doubt that the door will be open to moisture pushing
across the area from the Gulf of California and thunderstorm
outflows from the south and east of our area. In addition, with
high pressure building over Arizona, hot daytime temperatures will
return.

This afternoon and overnight...Look for isolated showers and
thunderstorms over the White Mountains into the early evening
then mainly ending. Gusty winds near any storms otherwise, mainly
fair weather.

Tuesday through Thursday...The chances for showers/thunderstorms
will slowly push west and northward through the period as moisture
flows in from the south and southeast. Activity will mainly be of
the afternoon and evening variety. The best chances at 40-60%
will remain over the eastern Mogollon Rim and White Mountains.
Elsewhere, storms will be more isolated with chances more in the
20-30% range. In addition, under strong high pressure it will be
hot. As a result, an Extreme Heat Warning is in effect for Tuesday
and Wednesday for the lower elevations of the Grand Canyon with a
watch for the same location on Thursday and Friday. Mountain
locations will see highs in the mid 80s to lower 90s, with the
lowest elevations achieving highs of 100 to around 110. The high
will be quite strong so there is some concern that the convective
environment will be somewhat capped. As a result, we`re not
anticipating any large thunderstorm blowups through this period
but with ample moisture, storms will be around.

From Friday onward...The high wobbles over the area and gradually
weakens. The environment will become more favorable for pushes of
moisture from the Gulf of California and stronger thunderstorms
over northwest Mexico. During this period we are expecting a
distinct ramp up of storm coverage/activity with strong
thunderstorms and heavy rain becoming more likely. The additional
storm activity will likely allow temperatures to cool a bit
heading into the weekend. As always, stay tuned.

&&

.AVIATION...Monday 18/18Z through Tuesday 19/18Z...Isolated
SHRA/-TSRA are expected from 20Z-03Z, mainly along and east of a
KSOW-KRQE line. MVFR visibilities are possible under the strongest
storms. Winds W/SW 5-10 kts from 18Z-02Z, otherwise VRB. However,
gusty and erratic winds possible in and around TS.

OUTLOOK...Tuesday 19/18Z through Thursday 21/18Z...Isolated to
scattered -SHRA/-TSRA are forecast each afternoon, mainly across
the higher terrain. MVFR visibilities are possible under the
strongest storms. Winds VRB 5-10 kts each day, but gusty and
erratic winds possible in and around TS.

&&

.FIRE WEATHER...Tuesday and Wednesday...Hot weather and low
afternoon humidity will persist on Tuesday and Wednesday, but with
chances for showers and thunderstorms spreading westward. On
Tuesday, the bulk of the storm activity is forecast to occur across
eastern Arizona, before expand further westward on Wednesday.
Otherwise, winds will generally be light and terrain driven, except
in the vicinity of storms due to strong outflows, with gusts in the
30-40 mph range possible. Minimum afternoon RH values 10-30%,
highest across the White Mountains.

Thursday through Saturday...Hot temperatures continue, along with
increasing chances for showers and thunderstorms, and a greater
potential for wetting rain each day. Winds will be primarily
variable at 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...McCollum
AVIATION...RR
FIRE WEATHER...RR

For Northern Arizona weather information visit
weather.gov/flagstaff