Hail in Arizona, September 19, 2025

Area Forecast Discussion
National Weather Service Flagstaff AZ
1024 AM MST Fri Sep 19 2025

.SYNOPSIS...Areas of showers and thunderstorms will continue
through the day today, before fading out over the weekend.
Unsettled conditions with seasonable temperatures look to
continue into early next week.

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.DISCUSSION...Today...As the remnant low from Tropical Storm
Mario moves northward through California, sub-tropical moisture
continues to be advected northward into Arizona. An area of steady
showers with some embed thunder has develop across northern
Arizona early this morning as result, and will continue to
traverse northeastward through the morning hours. An additional
complex of storms over the Phoenix Metro looks to move northward
this morning as well, brining another round of showers to the
area.

Rainfall rates have largely be 0.10-0.50"/hr this morning, with a
few heavier pockets embedded. This along with storm motions around 15
kts should limit the overall flash flood potential, at least outside
of any training storms or flood sensitive areas.

A brief lull is expected after daybreak, before another round of
scattered showers and thunderstorms develops during the afternoon
hours. This activity will likely be delayed given the lingering
debris clouds from activity this morning. Flash flooding will
continue to be the main threat, especially with training storms.
However, a few strong to severe storms will remain possible, mainly
over Yavapai and Gila counties where pockets of stronger instability
look to be present.

Saturday and Sunday...Heights look to rise slightly into the weekend
as high pressure builds to the south, while at the same time, an
upper-level low begins to eject off the Pacific. Our unsettled
pattern looks to remain as a result, with another surge of moisture
ahead of the low. As a result, daily chances for afternoon showers
and thunderstorms look to continue over the weekend, along with
seasonal temperatures.

Monday through Thursday...Solutions still look to diverge in exactly
what happens with the low at the start of next week. Much of the
operational guidance seems to stall it out just off the coast,
keeping the moisture pipeline into Arizona open. However, just how
long it stays stalled out remains in question. Nevertheless,
unsettled conditions with seasonable temperatures are expected as a
result.

&&

.AVIATION...Friday 19/18Z through Saturday 20/18Z...Expect mainly
VFR conditions. Areas SHRA/-TSRA could cause brief MVFR conditions
through 02Z, then clearing. Sfc winds not expected to impact flight
operations.

OUTLOOK...Saturday 20/18Z through Monday 22/18Z...Expect mainly VFR
conditions. Isolated -SHRA/-TSRA from 19Z-02Z Saturday, mainly south
of the I-40 corridor. Coverage potentially increasing during the
daytime hours Sunday and Monday. Sfc winds not expected to impact
flight operations.

&&

.FIRE WEATHER...Today and Saturday...Expect thunderstorms to
redevelop over much of central and northern Arizona by the
afternoon. Wetting rains are likely. Isolated thunderstorms will be
possible again on Saturday, but more confined to the higher terrain.
Minimum RH values will range between 30-50% today and 25-40% on
Saturday. Winds southwest to west at 5-15 mph with a few higher
gusts during the afternoon, light and variable or terrain driven
overnight.

Sunday through Tuesday...Look for isolated showers and thunderstorms
on Sunday and Monday, turning drier on Tuesday.  Minimum RH values
20-35% Sunday and Monday dipping to 15-25% on Tuesday. Winds
southwest at 5-15 mph gusting to 25 mph on Sunday then turning light
at 15 mph or less for Monday and Tuesday.

&&

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

&&

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

For Northern Arizona weather information visit
weather.gov/flagstaff