110
FXUS65 KPSR 041129
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
429 AM MST Mon Aug 4 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
  widespread Moderate HeatRisk each day.

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

- 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 Tuesday/...
Water vapor satellite imagery continues to show a defined ridge
centered over AZ, facilitating dry westerly winds aloft. Currently
models are showing PWAT values 20-50% of normal for this time of
year. With this dry air mass in place, no thunderstorm activity is
expected anywhere across Arizona today. This lack of moisture
will persist today through mid week resulting in more storm-free
days.

Yes, it`s dry, very dry, but the other concern for the next
couple of days is the heat. Afternoon high temperatures will
remain 3-8 degrees above normal as temperatures across the lower
deserts will be 110+. In addition to the highs, low temperatures
are also warming up with readings in the 70s across the rural
areas and lower to middle to upper 80s across the urban areas.
This will help keep the overall HeatRisk in the high-end Moderate
Category, however, given that the afternoon highs today and
Tuesday will not change much from the last of couple of days, the
Extreme Heat Warnings will continue in effect for the south-
central Arizona lower deserts to start the week ahead of the more
significant, impactful heat episode expected heading into the
middle portion of the week. Therefore, people are urged to take
all the necessary heat precautions such as limiting the time spent
outdoors and spending most of the time in air-conditioned places,
hydrating frequently, and wearing light, loose-fit clothing.

&&

.LONG TERM /Wednesday through Monday/...
Global ensembles show the center of the subtropical ridge of high
pressure migrating eastward into NM and strengthening during the
first part of the week. Ensemble and deterministic guidance
continue to show 500 mb heights climbing upwards of 598-600 dm by
the middle part of the week, which is in record territory for the
climatological period. With 500mb heights in that range, it will
drive temperature to further increase compared to the previous
days. This is expected to lead to high temperatures upwards of
113-118 by Thursday across the lower deserts. These temperatures
will challenge multiple record highs, with Thursday expected to
surpass the record of 112, in Phoenix, by several degrees. Little
overnight relief is expected with warm low temperatures in the
lower 90s in Phoenix. In addition to daily record highs likely
being challenged or broken, Phoenix may very well tie or break the
all-time hottest temperature recorded during the month of August.
The hottest Phoenix has ever recorded in the month of August was
117 degrees which has happened 4 times (2011, 2015, 2020, and
2023). Guidance then show the very strong ridge weakening for the
end of the week as a trough propagates through the northern
Rockies. This will lead to temperatures lowering, though still
remaining above normal.

With significant heat in the forecast, widespread Major to Extreme
HeatRisk will increase across much of the forecast area by Wednesday
with Thursday expected to be the hottest day. Extreme Heat Warnings
are in effect for much of south-central Arizona through Friday. The
warning will expand to include the higher terrain east of Phoenix
Tuesday through Friday and the remainder of the CWA by Wednesday.
Everyone should take this heat seriously and take the proper heat
safety actions to avoid heat-related health issues.

The positioning of the ridge will allow for some southerly moist
advection in the later part of the week, however, ensemble
guidance only show PWAT values to climbing to around 70-80% of
normal with PWATs around an inch. The lack of better moisture will
limit chances for monsoon activity with the best chances for
convection remaining across the Rim and down into southeastern
Arizona.

&&

.AVIATION...Updated at 0529Z.

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

No major aviation weather concerns will exist through the TAF
period. Winds will continue to follow typical diurnal trends with
periods of variability during diurnal transitions. Occasional
afternoon and early evening gusts around 15-20 kts are expected
across the Phoenix area terminals and upwards of 20-25 kts at KIPL
and KBLH. Skies will remain mostly clear outside of a few passing
high clouds.

&&

.FIRE WEATHER...
Unusually hot and dry conditions will continue for the start of
the week with temperatures gradually trending hotter through the
middle part of the week. MinRHs will fall into the 5-15% range
through the next couple of days, while MaxRHs range between 25-40%
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 through the first half of the week, before increasing into
the 113-118 degree range during the middle portion of the week.
Overall dry and hot conditions will continue for the upcoming 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...Ryan/Lojero
LONG TERM...Ryan/Smith
AVIATION...Smith
FIRE WEATHER...Ryan/Lojero