575
FXUS65 KPSR 010559
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1059 PM MST Sun Aug 31 2025

.UPDATE...Updated 06Z Aviation Discussion.

&&

.KEY MESSAGES...

- Warmer-than-normal temperatures will persist through today and
  tomorrow

- Generally dry conditions are expected to prevail over most of
  the region into the start of next week, with a slight chance of
  a shower or storm over the Arizona high terrain

- Chances for rainfall increase across the lower deserts by the
  beginning of the workweek as better moisture begins to envelope
  the Desert Southwest

&&

.SHORT TERM /Today Through Monday/...
Water vapor imagery continues to show a strong upper level ridge
over most of the western CONUS. This will continue to be the set
up this week with 500mb heights generally between 591-593dm. With
this high pressure in place, drier and warmer than normal
conditions will persist for the rest of today. Afternoon highs
today and tomorrow across the lower deserts are expected to be
between 105-110 degrees, around 4-5 degrees above normal for this
time of year.

Starting Monday, while the region will continue to be warmer than
normal, moisture will begin to increase as winds aloft begin to
shift out of the E to SE, allowing for moisture to be advected
into the region. Even with the uptick in moisture into the lower
deserts areas, most of the activity will be confined to the higher
terrains, east of the metro. However, there is still potential
for activity in the metro as hi-res guidance does show low chances
for some isolated storms to crop up. Any activity that does form
will most likely be short lived. With that being said the main
impact for the Phoenix Metro will be strong outflows from the
higher terrain areas. In fact, there is already a decent signal
from the HREF of one of these features extending down to the lower
deserts, highlighting most of Pinal and the eastern half of
Maricopa Counties in a ~40-50% chance of seeing wind gusts
reaching or exceeding 35 mph.

&&

.LONG TERM /Tuesday Through Saturday/...
Ensemble forecasts agree that moisture will continue to be on the
uptrend across the Desert Southwest heading into the middle of
next week, allowing for increasing shower and thunderstorm chances
for the region. Parts of the lower deserts may get in on the
action as early as Tuesday morning as there are signs that
isolated elevated convection, likely set-off by a mid-level wave
or perhaps a Sonoran MCV, will be seen over portions of Southwest
Arizona and Southeast California. Better moisture availability
will actually be over these areas mentioned above compared to the
remainder of our forecast area, so it is not out of the question
that areas around Joshua Tree NP, along with areas around the
Chocolate and Kofa Mountains, see daily isolated activity through
much of the week. The mountains of Gila County are also included
in on these daily shower and thunderstorm chances through the end
of the week.

Else where across the lower deserts of South-Central Arizona,
specifically the Phoenix metro, the best chances for rainfall
appear to be latter in the workweek, more toward the Thursday-
Friday timeframe as a reinforcing push of moisture pushes PWATs
closer to 1.5-1.8" or 150% of normal for the beginning of
September. Similar to Monday evening, storms outside of this
timeframe cannot be completely ruled out, but any convective
activity will be heavily reliant on outflow boundaries from
distant thunderstorm activity.

In terms of temperatures, there appears to be some good news for
fans of of more seasonal temperatures. The sub-tropical ridge is
projected to weaken slightly thanks to a disturbance expected to
develop off the Pacific Coast. This, combined with increasing
moisture levels, and the potential for greater rainfall coverage
and cloud cover, temperatures will gradually fall through the week
and into the weekend, with the potential for many areas not
reaching into the triple digits by as early as Friday.

&&

.AVIATION...Updated at 0559Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Easterly winds will prevail through midday Monday, with current
gusty winds expected to subside over the next few hours. Typical
afternoon west shift is not anticipated Monday. Instead a period
of light variability or light southerly component does look to
develop around mid to late afternoon. Good confidence for outflow
wind impacts Monday evening, with winds most likely from the east
to northeast. Timing as early as 00Z is possible, but 01-03Z is
most favorable at this time. Latest odds of outflow gusts >30kt
are around 40-50%. Confidence is too low for VCSH/VCTS mention in
the TAFs, as activity looks to dissipate as they drop toward the
Phoenix area. VFR conditions with cloud bases staying mostly at
above 10K ft AGL will prevail.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation weather concerns are expected through the next 24
hours under mostly clear skies. Winds will favor the W/SW at KIPL
through this evening before turning SE Monday morning. At KBLH,
winds will favor the SSW-SSE. Expect wind speeds to remain mostly
aob 7 kts, with periods of calm or VRB conditions at both
terminals.

&&

.FIRE WEATHER...
Generally dry conditions will persist through tonight. The best
chances of wetting rains starting Monday over the parts of Gila
County. Moisture levels will be on the rise over the next few
days, with MinRH values ranging between 10-15% today, increasing
to 20-30% by Tuesday. In turn, MaxRHs will follow a similar trend
with poor to modest overnight recoveries expected tonight into
Monday, becoming more decent by the middle of the week. This
increase in moisture will translate to a more active period of
monsoonal shower and thunderstorm activity. Temperatures over the
next week will peak today, with lower desert highs nearing 110
degrees, before gradually falling throughout the week toward
below normal levels.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$

SHORT TERM...Ryan
LONG TERM...RW
AVIATION...Benedict/Smith
FIRE WEATHER...RW/Ryan

NWS Phoenix Office