Flash Flood Warning 17, NWS Flagstaff, AZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
440 PM MST Thu Jul 17 2025

.SYNOPSIS...Scattered showers and thunderstorms expected into
this evening. Low grade monsoon conditions then set in starting
on Friday, lasting into early next week when shower and storm
activity will be mainly isolated. Cooler temperatures are also
expected into next week.

&&

.DISCUSSION...A low pressure system, currently centered along the
Baja California coast, will move northward over the coming days.
The low will move across southern California and into southern
Nevada from Saturday into Sunday, dissipating later on Sunday.
High pressure will then gradually build back over the southwest
states through next week.

For today and tonight...Deep moisture will remain across Arizona
in advance of the low. The result will be scattered showers and
thunderstorms into evening hours with the chance of a stray light
shower continuing through the night.

From Friday into Monday...The low will move northward into
California and Nevada. A drier air mass will accompany the
approaching low with diminishing chances for showers and
thunderstorms over much of northern Arizona. Moisture is likely
to linger over the eastern Mogollon Rim and White Mountains area
with scattered afternoon and evening thunderstorms continuing.
For the rest of northern Arizona the decrease in moisture will
result in generally only isolated activity. In addition, the wind
shear in the mid-levels transitions from around 10 mph at 600 mb
to near 50 mph at 400 mb over much of the area which is not
conducive to storm development in what will be a weak instability
regime.

From Tuesday onward...The low grade monsoon conditions could
continue. There will be an interaction between the subtropical
high pressure system to our east and a trough just off the west
coast. It may not be until late next week before the high can
nudge it's way westward into a position more favorable for the
transport of Gulf of California moisture northward. However, a lot
can change in the subtle/weak flow associated with the monsoon.

&&

.AVIATION...Friday 18/00Z through Saturday 19/00Z...VFR
conditions, a few scattered showers and thunderstorms a
possibility through 06Z. Shower and thunderstorm chances return
between 18Z and 20Z, lasting through rest of the afternoon. Winds
light and variable or terrain driven overnight, SW 5-10kts gusts
20kts after 18-20Z. Winds gusty and erratic with brief MVFR
conditions possible near thunderstorms.

OUTLOOK...Saturday 19/00Z through Monday 21/00Z...VFR conditions,
isolated to scattered afternoon showers and thunderstorms mainly
between 18Z and 03Z. Winds W-SW 5-15kts, gusts 20kts. Winds gusty
and erratic with brief MVFR conditions possible near
thunderstorms.

&&

.FIRE WEATHER...Friday and Saturday...Isolated to scattered showers
and thunderstorms are expected each afternoon and evening. Wetting
rains, gusty outflow winds, and flash flooding will be possible.
Daytime winds west to southwest at 5-10 mph with gusts to 10-20 mph
each day.

Sunday through Tuesday...Isolated to scattered showers and
thunderstorms are forecast, with the best chances over the eastern
Mogollon Rim and White Mountains. Wetting rains are likely within
any stronger storms. Daytime winds west to southwest at 5-10 mph
with gusts to 10-20 mph each day. Gusty, erratic winds possible in
and around thunderstorms.

&&

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

&&

PUBLIC...McCollum
AVIATION...Bernhart
FIRE WEATHER...McCollum

For Northern Arizona weather information visit
weather.gov/flagstaff