915
FXUS65 KPSR 030455
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
955 PM MST Sat Aug 2 2025

.UPDATE...Updated Aviation Discussion

&&

.KEY MESSAGES...

- Hot temperatures with lower desert highs exceeding 110 degrees
  will persist during the next several days, resulting in at least
  widespread Moderate HeatRisk each day.

- High-end Moderate to areas of Major HeatRisk will persist
  through early next week across south-central AZ with Extreme
  Heat Warnings in effect.

- A more significant, widespread Extreme Heat Episode is likely
  mid to late next week, with record high temperatures along with
  Major to locally Extreme HeatRisk.

- Overall dry conditions will prevail for much of the area during
  the next several days with any rain chances primarily confined
  to the higher terrain east of Phoenix.

&&

.SHORT TERM /Today through Monday/...
The latest objective analysis shows the subtropical ridge
centered near the international border with 500 mb heights at
around 597-598dm, with the strength of it being above the 99th
percentile for this time of the year. With the ridge positioned
this far south, dry west-southwest flow aloft continues to advect
dry air throughout the Desert Southwest with the latest SPC
mesoanalysis showing PWATs well under one inch across most
locations. Therefore, with this unusually dry air mass in place,
storm activity will be nonexistent across most areas with the
exception across the White Mountains and far southeast Arizona,
where isolated storms are likely this afternoon. Even drier air
is projected by the global ensembles to advect into the region on
Sunday with PWAT values expected to bottom out 20-40% of normal
for early August and thus storm activity will be absent
everywhere, including the high terrain. The well-below normal
PWATs will continue into Monday, with most if not all locations
likely to remain storm-free.

Aside from the unusually dry conditions in place, the main story
during this weekend and in fact through the upcoming work week will
be the heat. With the subtropical high as strong as it is, high
temperatures this afternoon are expected to peak between 110-114
degrees across the lower deserts. In fact there is a high chance,
(>70% chance) that Phoenix Sky Harbor may tie or even break the
daily record high of 113 degrees this afternoon. Temperatures of
these magnitudes will continue to result in widespread Moderate
HeatRisk with areas of Major HeatRisk to continue across south-
central Arizona. Heading into Sunday and Monday, the subtropical
high is expected to weaken just slightly, allowing afternoon high
temperatures to cool down a degree or two while morning low
temperatures will be about 4-5 degrees cooler given that the much
drier air mass in place will allow for more efficient radiational
cooling. This will cause HeatRisk levels across south-central
Arizona to be in the high-end moderate category. However, given
that the afternoon high temperatures for both Sunday and Monday
are not expected to be too indifferent from today and the HeatRisk
levels will be in the high-end moderate category, we have elected
to include Sunday and Monday in the Extreme Heat Warning across
the south-central Arizona lower deserts ahead of the more
significant, widespread Extreme Heat Episode expected mid to late
next week.

&&

.LONG TERM /Tuesday through Saturday/...
The primary weather concern will be the unseasonably hot
conditions during the upcoming workweek. Through the early part
of next week, ensemble guidance show the center of the subtropical
ridge of high pressure shifting eastward into southern NM while
strengthening. By the middle part of next week, ensemble and
deterministic guidance show 500 mb heights peaking around 598-600
dm. The strength of the ridge is likely to be in record territory
for the climatological period over the entire region Wednesday and
Thursday. Temperatures will quickly respond as daytime highs
across the lower deserts pushes to around 113-118 degrees. Record
highs are likely to be set with temperatures of this magnitude and
may tie or break the all-time hottest temperature for the month
of August in Phoenix. The hottest Phoenix has ever recorded in the
month of August was 117 degrees which has happened 4 times (2011,
2015, 2020, and 2023). Overnight lows are also expected to climb
into the lower 90s in Phoenix during this time, offering little
overnight relief. By the end of next week, the subtropical ridge
is expected to weaken, resulting in lowering temperatures.

With all that said, widespread Major to Extreme HeatRisk will
increase across most of the area by Wednesday and continuing through
Friday. Extreme Heat Warnings are in effect for all of south-
central Arizona Tuesday before expanding to include the entire
CWA Wednesday and continuing through Friday. Everyone should take
extra care next week to exercise heat safety to avoid heat-related
health issues.

The position of the ridge is expected to promote southerly moist
advection into the region going into Tuesday. Ensembles continue to
reflect a good deal of uncertainty in the amount of moisture we will
see pulled into the region. For now, the best chances for any
monsoon activity are expected to remain focused across the Rim and
down into southeastern Arizona.

&&

.AVIATION...Updated at 0455Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT; and
Southeast California/Southwest Arizona including KIPL and KBLH:

No major aviation concerns are anticipated through Sunday
evening under clear skies. Winds will follow typical diurnal
trends for this time of year, with periods of variability,
especially during the overnight and early morning hours, and
afternoon gusts in the mid-teens to around 20 kts.

&&

.FIRE WEATHER...
Drier conditions will continue to settle in this weekend with only
a small chance for an isolated shower or thunderstorm across
southern Gila County this afternoon. Min RHs will fall into the
5-10% range this weekend, while Max RHs range between 20-30% for
most areas. Winds will generally follow diurnal tendencies with
typical afternoon upslope gustiness. Temperatures will remain
above normal with lower desert highs mostly between 108-114
degrees. Overall dry and hot conditions will continue into next
week with any rain chances remaining mostly confined to the higher
terrain east of Phoenix.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning from 10 AM Wednesday to 8 PM MST Friday for
     AZZ530>533-535-536.

     Extreme Heat Warning until 8 PM MST Friday for AZZ534-537>544-
     546-548>555-559.

     Extreme Heat Warning from 10 AM Tuesday to 8 PM MST Friday for
     AZZ545-547-556>558-560>563.

CA...Extreme Heat Warning from 10 AM Wednesday to 8 PM PDT Friday for
     CAZ560>570.

&&

$$

SHORT TERM...Lojero
LONG TERM...Smith/Lojero
AVIATION...RW
FIRE WEATHER...Smith