Flash Flood Warning 63, NWS Phoenix, AZ

Area Forecast Discussion
National Weather Service Phoenix AZ
916 AM MST Wed Sep 16 2026

.UPDATE...Updated 18Z Aviation Discussion.

&&

.KEY MESSAGES...

- Scattered to widespread showers and storms are forecast to
  develop today across Arizona, with potential for areas of high
  rainfall amounts leading to flash flooding.

- A Flood Watch is in effect through early tonight across much of
  southern Arizona.

- Shower and thunderstorm chances will greatly diminish by
  Thursday and come to an end starting Friday with much drier
  air moving in and lasting through at least this weekend.

- Below normal temperatures are expected today across south-
  central Arizona, before warming back to to slightly above
  normal levels by the weekend.

&&

.SHORT TERM /TODAY THROUGH FRIDAY/...

There is potential for a very active and highly impactful weather
day across much of Arizona today. Considerable and potentially
deadly flash flooding is in the cards for today. Hi- res modeling
continue to show scattered to widespread showers and
thunderstorms eventually developing today across the region and
leading to many areas receiving 1-3 inches of rain which will
likely result in flash flooding. Where these hi-res CAMs have
struggled so far is timing out initial convective development.
Previous model runs suggested Tuesday afternoon was going to be
very active across south-central AZ, as well as early this
morning, which has not quite come to fruition. While objective
analysis shows moisture and instability have been favorable and
continue to be favorable this morning, there has not been much in
the way of forcing/lift. This is expected to change today though.
A well defined low pressure circulation is seen on satellite along
the west coast of Sonora, MX. This feature is forecast to move
straight north up through AZ likely this afternoon through tonight
and help provide the lift that has been somewhat lacking. There
will also be increased jet support with a strengthening of the
200mb jet and entrance region of the jet setting up over south-
central AZ. So, the ingredients will all be there for strong
showers and storms to develop, but there has still been a little
bit of uncertainty with timing of greatest coverage and impact of
showers and storms. Latest NBM PoPs are highest in the 5AM-11AM
timeframe for the Phoenix area and the 00Z hi-res models show
highest QPF in this timeframe as well, but conceptually, based on
the setup, the best timing for south- central AZ looks to be more
from midday through this evening.

A Flood Watch is currently in effect for south-central AZ and
will continue through 11 PM MST tonight. The watch was issued
largely due to the synoptic and mesoscale setup being supportive
of scattered to widespread showers and storms capable of producing
1-hr rain rates up around 1-2" and higher over shorter time
frames. Hi-res modeling continues to show QPF upwards of 1-3" over
a large portion of south-central AZ, and there are even high end
amounts up to around 4" (10% chance). Rainfall amounts are still
likely to vary widely, with some areas potentially missing out and
receiving little to none. The Flood Watch has been expanded to
include portions of La Paz and Yuma Counties starting at 11AM and
also going through 11 PM. Several of the latest hi-res models have
supported training storms in this area. This area is also
forecast to have higher instability and receive better daytime
heating with more sunshine heading into the afternoon. Any storms
that develop in this area may actually have the highest rain rates
but be more isolated in coverage. WPC's updated Day 1 ERO
expanded the coverage of both Slight and Moderate Risk areas. The
Moderate now includes all of Gila and Pinal counties and most of
Maricopa County. The last time a Moderate Risk covered this area
was back in 2022.

The heavy rain threat looks like it will come to an end across
south-central AZ later this evening and tonight, once the low
circulation moves north of the area, the environment becomes
overworked, and subsidence increases on the back side of the low.
Still, a narrow axis of showers and storms may linger into the
overnight hours, most likely toward eastern AZ. Drier air will
begin moving in aloft through the day Thursday with increased
west-southwest flow, which will limit showers and storms mostly
to northern AZ high terrain. Further drying of the entire column is
expected through Friday, with mixing ratios dropping to or below 8
g/kg and PWATs falling below 1.00" by the end of the day which
will hurt any chance at rain even in the high terrain.

Temperatures this afternoon may struggle to reach 90 degrees
across south-central AZ, with ample cloud cover and rain around,
while areas further west, with more sun, still warm into the
middle 90s to around 100 degrees. Temperatures will warm back up
by the end of the week, but only back to around seasonal levels,
with highs around 100 degrees across the lower deserts, as broad
troughing remain in place across much of the west.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...

The monsoon pattern may be done after today, shifting into the
transitional season with more frequent troughs. Dry air will
continue to spread across the region through this weekend with
PWATs forecast to drop below normal, as low as 0.4-0.7" across the
lower deserts. The will inhibit any chance at rain. The broad
trough moving through the West, helping drive the westerly flow
and dry air, is expected to shift east into the Plains by the
start of next week. Global ensemble guidance then shows an upper
low moving out of the Pacific toward the SoCal coast by the end of
the day Monday. There is still plenty of uncertainty regarding
this low this far out, but it may be what helps eventually drive
moisture back up in the deserts and drive the next chance at rain.
Average to slightly above average temperatures are forecast this
weekend through the first half of next week with this forecast,
with afternoon highs around to slightly above 100 degrees. With
the drier air coming in, the morning lows will finally be more
pleasant, consistently dropping into the 70s for most lower
desert locations.

&&

.AVIATION...Updated at 1615Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Forecast continues to remain on track with major operational
impacts likely this afternoon through this evening. Clusters of
thunderstorms are expected to develop within the vicinity in the
next couple of hours with the current guidance indicating the
highest direct impacts likely by the mid to late afternoon hours
and possibly lingering into the evening hours. Overall wind
direction should remain out of the southeast before activity
materializes with the potential for gusty and erratic winds as
thunderstorm activity increases in coverage within the vicinity.
For most of the period, winds should generally maintain an
easterly component.

In addition to direct thunderstorm impacts, instances of MVFR and
possibly brief IFR flight categories are possible in the form of
lowered CIGs (as low as 4-5 kft with TSRA) and visibilities.
SHRA activity will likely linger well into the evening and
overnight hours with lower probabilities of TSRA and thus have
maintained a prob30 mention for this evening for TSRA as there is
high uncertainty. VCSH look to linger through 10-12z Thursday
morning with BKN CIGs between 5-7 kft looking to linger before
scattering out by the mid to late morning hours.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major weather issues will exist through the TAF period under
mostly clear skies, with FEW low (aoa 7-9 kft) and high clouds
moving in at the end of the TAF period. At KIPL, winds will
generally be out of the southeast with some gusts into the mid to
upper teens later this afternoon through early this evening. At
KBLH, southerly winds are expected through the afternoon with
periodic gusts between 20-25 kts. There continues to be increasing
confidence that an outflow from the convective complex in AZ will
likely affect KBLH by the early evening hours, shifting the winds
more out of the east with potentially some gusts between 20-25 kts
and maybe some reduced visibilities due to some BLDU, although
confidence of BLDU materializing is low at this time. Winds across
both terminal sites should become mostly light and variable during
the overnight and early morning hours.

&&

.FIRE WEATHER...
Periods of scattered to widespread showers and thunderstorms are
expected today, focusing mostly across the eastern districts this
afternoon through this evening. There will be a heavy rainfall
and flood threat with the activity. Moisture levels will be
elevated most areas, highest across eastern districts, where
minimum RH this afternoon will be around 50-60%. Minimum RHs will
be lowest across southeast CA, with values around 20-30%. A drying
trend will begin Thursday with conditions becoming very dry by
this weekend. Minimum RHs by Saturday dip to 10-25% across the
lower deserts (lowest across western districts). Overnight
recoveries will still be good across eastern districts this
weekend at 40-60%, while western districts hover around 25-45%.
The drier air moving in will eliminate rain chances by Friday,
with low chances in Gila County Thursday afternoon. Winds will
favor the south to southeast over much of the area through
Wednesday with gusts of 20-30 mph at times across southwest AZ and
southeast CA. In the following days winds will return to a more
typical diurnal with modest afternoon upslope gustiness.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Flood Watch through this evening for AZZ531-533-536.

     Flood Watch through this evening for AZZ534-537>563.

CA...None.

&&

SHORT TERM...Benedict
LONG TERM...Benedict
AVIATION...Lojero
FIRE WEATHER...Benedict

Special Weather Statement
National Weather Service Phoenix AZ
924 AM MST Wed Sep 16 2026

AZZ556-558-562-563-161700-
Southeast Gila County AZ-Tonto Basin AZ-Globe/Miami AZ-
Pinal/Superstition Mountains AZ-
924 AM MST Wed Sep 16 2026

...A STRONG THUNDERSTORM WILL IMPACT GILA COUNTY THROUGH 1000 AM
MST...

At 924 AM MST, Doppler radar was tracking a strong thunderstorm 10
miles southeast of Tonto National Monument, or 12 miles southeast of
Roosevelt, moving north at 10 mph.

HAZARD...Wind gusts up to 50 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Roosevelt Estates.

This includes AZ Route 188 between mile markers 222 and 238.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3344 11090 3348 11104 3366 11108 3361 11081
TIME...MOT...LOC 1624Z 189DEG 7KT 3354 11098

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPH

GL