961
FXUS65 KPSR 031947
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1247 PM MST Sun Aug 3 2025

.UPDATE...Updated Short-Term 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.

- A more significant, widespread Extreme Heat Episode is likely
  mid to late 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 water vapor satellite imagery as well as streamline
analysis show the center of the subtropical ridge centered over
southern AZ. The positioning of the ridge over southern AZ continues
to promote westerly flow aloft, which in turn has advected very dry
air over the region. To put into perspective how dry the air mass
overhead is currently, the 12z PHX Sounding measured PWATs of
0.33", which is near the climatological minimum for early August
with this quantity of moisture more typical for late Spring. With
this dry air mass in place, no thunderstorm activity is expected
to fire anywhere across Arizona today. The well-below normal
moisture levels will persist into Monday leading to another day of
storm-free activity once again.

Aside from the dry conditions in place, the main story continues to
be the heat. Afternoon high temperatures will remain above normal as
readings top out above 110 degrees across the lower deserts with
overnight lows through Monday near normal with readings in the 70s
across the rural areas and lower to middle 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
Monday 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 /Tuesday through Sunday/...
Global ensembles show the center of the subtropical ridge of high
pressure shifting eastward into NM while also 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. Given the strength of
this anomalously strong ridge, temperatures will quickly respond
climbing upwards of 113-118 degrees across the lower deserts by
Thursday. Temperature readings of this magnitude will likely
challenge multiple record highs and likely shatter the record of
112 degrees on Thursday in Phoenix. Warm low temperatures in the
lower 90s in Phoenix will provide little overnight relief during
this heat event. 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, however, ensemble guidance only show PWAT values to
climbing to around 70% 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 1710Z.

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

No major aviation concerns will exist through Monday afternoon
under clear skies then FEW passing high cirrus Monday. Winds will
continue to follow typical diurnal trends for this time of year,
with periods of variability during transitions between E/SE and
SW/W. Occasional afternoon/early evening gusts into the upper
teens are anticipated.

&&

.FIRE WEATHER...
Unusually hot and dry conditions will continue for the start of
the new week with temperatures gradually trending hotter through
the middle part of the week. MinRHs will fall into the 5-10%
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...Lojero
LONG TERM...Smith
AVIATION...Whittock
FIRE WEATHER...Smith/Lojero