730
FXUS65 KPSR 081757
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1057 AM MST Tue Jul 8 2025

.UPDATE...Updated 18z Aviation Discussion.

&&

.KEY MESSAGES...

-Strong high pressure over the region will result in well above
 normal temperatures through midweek with afternoon highs
 forecast to reach and exceed 115 degrees across many of the lower
 desert communities Wednesday

-The heat will result in widespread Major HeatRisk with Extreme
 Warnings in effect for much of the region today through Thursday

-Slightly cooler temperatures expected by the end of the week
 through this weekend, but remaining above normal

-Thunderstorm activity will continue to be limited to the Arizona
 high terrain and southeast Arizona during the next several days

&&

.SHORT TERM /TODAY THROUGH WEDNESDAY/...
Latest water vapor satellite imagery as well as objective
analysis show the subtropical high situated across eastern AZ,
with 500 mb heights around 595dm, while a cutoff low pressure
system remains situated off the central CA coast. The cutoff low
is forecast to weaken throughout the day today, which will allow
the subtropical high to expand westward and strengthen even more
as 500 mb heights increment to 596-598dm. As a result of the
strengthening high, afternoon high temperatures today are forecast
to be 2-4 degrees warmer than yesterday with many of the lower
desert locations ranging between 109-113 degrees. The hottest
locations will be over south-central AZ, where areas of Major
HeatRisk will materialize and thus Extreme Heat Warnings will go
into effect starting later this morning across the lower deserts
of Maricopa and Pinal Counties and the San Carlos area of Gila
County.

As the high continues to expand westward and strengthen slightly,
Wednesday is expected to be even hotter and the peak of the
extreme heat episode. Many of the lower desert locations are
forecast to see highs of 115+ degrees. This will result in
widespread Major HeatRisk across the majority of the region and
thus the areal coverage of the Extreme Heat Warning expands to
include all the lower deserts as well across the higher terrain
areas east of Phoenix below 4000 feet with a Heat Advisory in
effect for elevations above 4000 feet. Daily record highs are
likely to be challenged in both Phoenix and El Centro.

In terms of thunderstorm activity, strong subsidence from the
strengthening high and meager moisture will hinder the potential
for any widespread activity. Any thunderstorm activity during the
next couple of days will be confined mainly to the High Country,
the White Mountains, and the southeastern third of AZ.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
The subtropical high is expected to weaken slightly heading into
Thursday as the energy leftover from the cutoff low migrates
eastward into the Great Basin and Intermountain West Regions. This
will result in a slight decrease in the heights aloft and thus
afternoon high temperatures will be slightly cooler but still hot
enough for areas of Major HeatRisk to remain in place with
Extreme Heat Warnings remaining in effect for all of the lower
desert communities. Heading towards the end of the week through
next weekend, the high will continue to very gradually migrate
westward towards the southern CA coastline and as a result heights
aloft will continue to decrease slightly more. This will
translate to slightly cooler temperatures, but still remain a few
degrees above normal as afternoon highs across the lower deserts
will average around 110 degrees, resulting in widespread Moderate
HeatRisk.

With the subtropical high migrating westward into southern CA
towards the end of the week and weekend, the upper-level flow
pattern will remain quite unfavorable for any deep moisture
influx. Thus conditions are expected to remain mostly dry across
much of the region, with any thunderstorm activity limited across
the White Mountains through the southeastern third of AZ. As the
high migrates into the southern CA coastline during the weekend,
the upper-level flow is expected to turn out of the north, which
will bring in even drier air with the latest EPS and GEFS showing
PWATs dropping below one inch. Thus, thunderstorm activity will
likely be more limited, even across the higher terrain areas. This
overall dry pattern will continue into early next week before the
high potentially repositions near the Four Corners by the middle
to latter half of next week, which if it materializes, would be a
more favorable flow pattern to advect deeper moisture into the
region and reintroduce higher thunderstorm chances.

&&

.AVIATION...Updated at 1755Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
No major aviation weather concerns will exist through the TAF
period under FEW mid and high clouds. Winds will predominantly
favor the W/NW through this evening. Followed by winds going light
and variable during the overnight hours at KSDL and KDVT, KPHX
going light and variable around sunrise, and KIWA going light
southeasterly during the overnight hours. Expect gusts to around
20 kts this afternoon into the early evening.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation weather concerns are expected through the next
24 hours under periods of FEW to at times SCT mid and high clouds.
Winds will continue to vary between S/SE and SW, with extended
periods of light and variable winds, particularly at KIPL. Wind
speeds will generally remain AOB 10 kts, though some gusts to
around 15-20 kts are possible, particularly after the switch to a
SW`rly direction this evening.

&&

.FIRE WEATHER...
Generally dry conditions and above normal temperatures will
persist during the next several days as lower deserts highs reach
and exceed 110 degrees each day. MinRH values will generally be
in the teens each day, while MaxRH values will be the lowest
tonight and Wednesday night at 20-40% and then increase up to
30-50% the rest of the week for most of the area. The exception
will be across Imperial and southern Yuma Counties where periodic
gulf surges will result in MaxRH values in excess of 50%. The
overall wind pattern will follow the familiar diurnal trends, with
some afternoon/early evening breeziness. A slight uptick in the
winds is expected, especially on Thursday afternoon, which may
lead to locally elevated fire weather conditions in the afternoon.
Very minimal rain chances will exist during the next several days
with CWR <10% through at least next weekend.

&&

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

     Extreme Heat Warning until 8 PM MST Thursday for AZZ534-537>540-
     542>544-546-548-550-551-553>555-559-560.

     Heat Advisory from 10 AM to 8 PM MST Wednesday for AZZ557-558-
     563.

     Extreme Heat Warning from 10 AM to 8 PM MST Wednesday for AZZ541-
     545-547-549-552-556-561-562.

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

&&

$$

SHORT TERM...Lojero
LONG TERM...Lojero
AVIATION...Berislavich/Whittock
FIRE WEATHER...Lojero/Benedict