360
FXUS65 KFGZ 170759
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
1259 AM MST Wed Sep 17 2025

.SYNOPSIS...Slight chance of showers and thunderstorms over the
eastern Mogollon Rim and White Mountains today, before moisture
and chances for storms increase over the coming days. Cooler
temperatures and generally light winds are expected to close out
the week.

&&

.DISCUSSION...Today...An elongated, but narrow, ridge of high
pressure remains situated over the southwest today. The resulting
northwesterly flow has consequently ushered in drier air into much
of northern Arizona, however a sharp north-south moisture gradient
is in place. Currently, surface dewpoints are near 20-30F from
I-40 and north, 30- 40F across Yavapai County and as high as 50F
across the southern portions of Navajo and Apache counties. With
this boundary in place, storm coverage this afternoon looks to be
minimal, and mainly focused across areas east of I-17 and south of
I-40.

Thursday and Friday...The remnant low of what was Tropical Storm
Mario is currently situated about 1/2 way up Baja California.
Latest guidance seems to have shifted the track further westward into
southern California, and thus shifting the focus of precipitation
with it.

An initial band of showers and thunderstorms look to develop over the
Lower Deserts early Thursday, aided by the large-scale ascent ahead
of the low. As this moves northward, isolated to scattered storms
look to develop by the late morning and early afternoon mainly south
and west of a line from the Grand Canyon to Flagstaff to St. Johns.
Rain looks to continue into the overnight as sub-tropical moisture
continues to be advected northward, now that the high has been
displaced. As a result, Friday looks to be the best shot at area-
wide showers and thunderstorms with better moisture in place. While
the remnant low has largely been absorbed into the mean flow, upper-
level divergence in the left-exit region of the jet streak should
still be enough to provide some large-scale dynamics to aid
precipitation development.

Saturday through Tuesday...Heights look to rise over the weekend and
into early next week as high pressure tries to build over the
southwest US once again. At the same time, an upper-level low looks
to sit off the California coast. Of the operational 00Z guidance,
the GFS and ECMWF both seem to have trended towards a slower
ejection of the low and a more amplified ridge, while the CMC ejects
the low off the Pacific into southern California. Solutions become
even less clear looking at the ensemble, with some members between
the EPS, GEFS, and CMCE showing a significant downward trend in
PWAT, while another handful show the moisture remaining over
northern Arizona.

With this in mind, the current forecast of warming temperatures and
minimal precipitation chances seems reasonable for the extended
period.

&&

.AVIATION...Wednesday 17/06Z through Thursday 18/06Z...VFR
conditions are forecast. Look for isolated -SHRA/-TSRA Wednesday
afternoon, mainly near and south of a KPAN-KJTC line. Daytime
winds west to northwest at 5-15 kts, turning light and variable at
night.

OUTLOOK...Thursday 18/06Z through Saturday 20/06Z...Mainly VFR
conditions are expected. On Thursday, scattered SHRA/TSRA mainly
south of Interstate-40, then spreading across all of northern
Arizona Thursday night and Friday. Wind gusts of 25-35 kts and
MVFR conditions possible in and around storms. Daytime winds west
to southwest at 5-15 kts on Thursday and Friday, light and
variable at night

&&

.FIRE WEATHER...Today and Thursday...Warm and mainly dry
today, outside of a slight chance for showers and thunderstorms,
mainly across the eastern Mogollon Rim and White Mountains. Cooler
temperatures and scattered storms expected on Thursday, especially
south and west of the Mogollon Rim. Southwest through northwest winds
5-15 mph each day.

Friday through Sunday...Cooler. Chance for showers and thunderstorms
each day, with best chance for wetting rains on Friday. Wind
south/southwest 5-15 mph on Friday, becoming west over the weekend.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...None.

&&

$$

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

For Northern Arizona weather information visit
weather.gov/flagstaff