264
FXUS65 KPSR 301750
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1050 AM MST Sun Aug 30 2026

.UPDATE...Updated 18Z Aviation Discussion.

&&

.KEY MESSAGES...

- Active weather will persist through Monday with periods of
  showers and thunderstorms, some potentially producing strong
  winds and heavy rainfall across south-central Arizona.

- A Flood Watch is in effect for south-central Arizona for Sunday
  evening into Sunday night as heavy rainfall could result in
  localized amounts in excess of 1-2 inches and flash flooding.

- Near to slightly below normal temperatures are expected for the
  first part of this week before returning to slightly above
  normal during the latter part of the week as drier conditions
  settle over the region.

&&

.SHORT TERM /TODAY THROUGH MONDAY/...
The atmosphere will remain well primed for additional rounds of
showers and thunderstorms today and Monday with heavy rainfall a
continued concern across south-central and eastern Arizona.
Current objective analysis shows the subtropical ridge now
positioned across the Southern Plains, but still extending into
southeast Arizona. A Pacific trough centered over the Pacific
Northwest is slowly making headway through the Western U.S. with
the southern fringes of the trough now moving into northwest
Arizona and southern California. Moisture levels did improve a bit
on Saturday, but we are still fighting against some drier air
aloft getting pulled in from the southwest. Very strong heating on
Saturday definitely helped to raise instability levels and much
of that remains, except for far eastern Arizona where widespread
rainfall occurred.

South southwesterly flow today into Monday should improve lower
level moisture across most of Arizona, but the drier air aloft
will continue to stream into southern California into western
Arizona. Low level mixing ratios through Monday are forecast to
be between 10-12 g/kg, just enough to worry about a heavy rainfall
threat due to the forecast MUCAPE of 1000-1750 J/kg across the
area. Yesterday`s heavy rainfall only affected higher terrain
areas as there just wasn`t enough lift to get storms to fire early
enough over the lower deserts, but that should change today.

Guidance shows a strengthening upper level shortwave moving into
central California later today, while a secondary jet max will be
positioned to our north/northeast. The shortwave to our west is
not expected to help until at the earliest Sunday night, but the
jet max to our north will at least position central and eastern
Arizona in a favorable area of ascent. Assuming near optimal
heating conditions today, at least over south-central Arizona,
forecast MUCAPEs should rise to around 1500 J/kg by late afternoon
providing plenty of instability for storms to develop. Forecast
soundings also show very little CIN during the latter half of the
afternoon which should even allow for some scattered storms to
initiate over the lower deserts. CAMs, especially the 06Z HRRR,
show widespread showers and storms developing late in the
afternoon across Pima, Pinal and Gila Counties before spreading
north and northwestward through much of Maricopa County in the
evening. A few storms may become strong enough to drop 50+ mph
winds with western Pinal and southern Maricopa Counties likely
being the best area for the strongest winds and dust to occur.

Given the amount of instability and moisture levels reaching
above normal for late August, we are anticipating some areas will
receive heavy rainfall this evening into early tonight. Another
Flood Watch has been issued for Maricopa, Pinal, and Gila Counties
for this evening into tonight with localized 1-2 inch amounts
quite possible focused across western Pinal through central
Maricopa County this evening and then over northern Maricopa
County during the early overnight hours. We also can`t rule out
the possibility of storms lasting longer Sunday night as the
shortwave trough will be getting closer to western Arizona, but
eventually we should exhaust most of the available instability.

Monday`s forecast remains more uncertain as it seems likely
today/tonight will be very busy resulting in a somewhat work-over
atmosphere going into Monday morning. However, guidance still
shows ample moisture on Monday with even better moisture in the
mid levels compared to today. Cloud cover will likely be an issue
for at least eastern Arizona limiting heating and instability, but
there should be decent heating and recovery over south-central
Arizona. The track of the shortwave trough takes it more into
southern Nevada into Utah during the first half of Monday putting
northern Arizona more in the prime area better shear and stronger
storms. Despite the shortwave brushing past to the northwest, we
should again fall within a fairly favorable area of ascent over
central Arizona due to the position of the jet max over western
Utah/northwest Arizona. Monday`s storm potential is expected to be
more conditional and more scattered compared to today, but it
would not be surprising to see a few strong storms and localized
heavy rainfall again. In fact, the forecast sounding for Monday in
Phoenix looks nearly identical to today.

Temperatures are finally starting to cool off with the exit of the
ridge and the increased rain activity. Highs today are expected to
top out at around 105 degrees in the Phoenix area to 106-110
degrees across the western deserts. Monday should be the `coolest`
day of the week with the NBM calling for highs in the mid to upper
90s for Phoenix to right near normal for the western lower
deserts.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
A much quieter period of weather is anticipated starting Tuesday
as the flow turns more out of the west southwest ushering much
drier air through the rest of the area. Forecast PWATs are
expected to drop to just below normal on Tuesday, likely staying
on the lower side through around Thursday. NBM PoPs drop off to
mostly below 10% starting Tuesday and carrying through at least
Wednesday. Temperatures will also be a bit slow to warm back up as
the trough will still have some influence over our region.
Forecast highs return back into the normal range by Wednesday,
while overnight lows will be a more comfortable upper 70s to low
80s for the lower deserts.

High model uncertainty becomes an issue late week into next
weekend as models are currently favoring a tropical cyclone to
move northwestward off the coast of Baja and potentially even
getting close to California early during the following week. It is
impossible to know at this point where this TC will go, but it at
least seems fairly likely it will help to direct moisture
northward into our region by next weekend. Assuming this occurs,
we may eventually return to busy monsoon weather.

&&

.AVIATION...Updated at 1750Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:

The main aviation concern this forecast period will be another round
of thunderstorms, gusty outflow winds, and blowing dust starting
potentially as early as late this afternoon and lasting through much
of tonight. Until then, VFR conditions with a typical diurnal wind
pattern is anticipated. Winds will shift out of the WSW this
afternoon. Intermittent gusts into the teens to around 20 kts can
be expected by the late afternoon period.

Heading into this evening, an active period of weather is likely
with TS and BLDU becoming the main hazards. Latest model guidance
suggests TS will develop to the south of the terminals and gradually
build into the Phoenix Metro along a northward progressing outflow.
For now, the best timing of arrival of any outflows and
subsequent TS looks to be around 01Z at KIWA and 02Z at the
remaining TAF sites. Due to some uncertainty, timing may need to
be adjusted in later issuances. Strong S-SE winds >30 kts will
likely accompany the outflow along with vsbys around 3-5 SM in
BLDU. Periods of VCTS/TSRA can also be anticipated and will last
for several hours. Another round of SHRA may also develop around
the 06-10Z timeframe. However, this is highly dependent on how
storms progress this evening. SCT mid/high cloud decks will be
common through the period, with the lowest CIGs forecasted at
09-10kft during thunderstorm activity.

Southeast California/Southwest Arizona including KIPL and KBLH:

No major aviation concerns are expected at the SE California
terminals. At KIPL, winds will fluctuate between westerly and
southeasterly with westerly winds increasing again by this evening.
At KBLH, winds will fluctuate between southerly and southwesterly
through the TAF period. Speeds will be elevated (10-15 kt) most of
the period with some gusts of 20-25kt during the afternoon and early
evening. Skies will be mostly clear with FEW mid and high clouds
moving into the region by this evening.

&&

.FIRE WEATHER...
Elevated moisture and rain chances will persist across the eastern
districts through Monday with gusty winds, heavy rainfall, and
localized flooding still a threat. The western districts will
generally stay dry with at most a few isolated showers and storms.
Expect MinRHs of 15-20% across the western districts to 25-40%
over the eastern districts before drying out again beginning
Tuesday. Temperatures will range from around normal over western
districts to slightly below normal over the eastern districts.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Flood Watch from 6 PM MST this evening through late tonight for
     AZZ534-537-538-540>563.

CA...None.
&&

$$

SHORT TERM...Kuhlman
LONG TERM...Kuhlman
AVIATION...95/Berislavich
FIRE WEATHER...Kuhlman