735
FXUS65 KPSR 101817
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1117 AM MST Thu Jul 10 2025

.UPDATE...Updated 18Z Aviation Discussion...

&&

.KEY MESSAGES...

- Though temperatures will lower several degrees today from their
  peak yesterday, they will still be well above the daily
  normals, and so Extreme Heat Warnings remain in effect for much
  of the area through this evening.

- Temperatures Friday onward will be fairly stable, with lower
  desert highs generally in a 105 to 110 degree range heading into
  early next week.

- Thunderstorm activity will remain limited to the Arizona high
  terrain and portions of Southeast Arizona through this weekend,
  with minimal activity today and Friday.

&&

.SHORT TERM /TODAY THROUGH FRIDAY/...
Current wv satellite imagery reveals a rather compact shortwave
traversing the intermountain west and northern portions of the
Great Basin, with the center of an anticyclone (now flattened by
the shortwave to its north) still overhead and gradually sliding
westward. With H5 heights aloft in a 594-597 dam range today, down
from the broad area of 597-598 dam values observed yesterday, we
can expect afternoon highs several degrees cooler than the record-
breaking values we saw yesterday, though still well above normal
for the time of year. The latest NBM continues to advertise lower
desert highs in a 110-115F range, with better probabilities of
seeing 115+F focused along the Lower Colorado River Valley and
portions of Southeast CA. With temperatures remaining this hot,
areas of Major HeatRisk still linger today across much of the
area, and so Extreme Heat Warnings remain in effect through this
evening. By Friday, the subtropical high will have migrated to the
vicinity of the SoCal Coast, and so H5 heights will continue to
fall, reaching a 592-595 dam range for the weekend. As such,
expect afternoon highs to respond by falling into a 105-110 degree
range Friday onward. Thermal profiles do not typically respond
this quickly, though models have consistently depicted a surge of
low level moisture spreading across South-Central AZ tonight, and
with this moisture in place through much of the day Friday,
temperatures will not respond as quickly to daytime heating as
they would if it were drier.

The shortwave traversing the northern portions of the Great Basin
today will act to increase winds aloft, bringing enhanced
afternoon/evening breeziness to the region. Global guidance
depicts a very subtle tightening of the pressure gradient at
midlevels, with 700 mb flow increasing to 20-25 kts. Though this
is not particularly impressive, deep mixing heights this time of
year mean that this higher momentum air even in the midlevels can
reach the surface, and so afternoon/early evening gusts to 25-30
mph will become quite common, with even higher gusts to 35 mph
over the AZ high terrain. In combination with low humidity,
anticipate locally elevated fire weather concerns due to this
enhanced breeziness this afternoon into the evening.

Thunderstorm activity will be quite minimal over the state today
and Friday. Subsidence from the proximity of the subtropical high
will preclude the development of storms over much of the AZ high
terrain today, and as the high slides westward over the SoCal
coast Friday, there will be a a surge of low level moisture, but
winds aloft shift out of the northwest, effectively drying out the
midlevels. With this combination of factors, it is not surprising
that the latest HREF reflectivity >40 dBZ paintball plot depicts
very little development through Friday, except perhaps over the
White Mountains and over southern Cochise County.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
The convective potential through the weekend will continue to be
very limited as the upper-level flow pattern will remain
unfavorable for any deep moisture influx. In fact, as the high
settles over the southern CA coastline, the flow will turn out of
the north, bringing drier air with PWATs dropping below one inch
during the weekend. However, enough low-level moisture may still
be present for some afternoon convection to materialize, mainly
across the vicinity of the White Mountains and the southeastern
third of AZ. Heading into next week, model guidance continues to
show the high repositioning towards the Four Corners Region,
especially by the middle of the week. This would result in a more
favorable flow pattern for deeper moisture advection, with
convective coverage on the increase across the higher terrain and
foothills initially before chances increase across the lower
deserts, more likely by the latter half of the week. Recent
deterministic runs of the GFS and perhaps less apparent but
present in the ECMWF suggest that an easterly wave may propagate
through the forecast area Wednesday-Thursday, helping to increase
moisture and act as a focus for convective initiation if the
timing is right. The details are quite uncertain this far out, but
the potential exists for some thunderstorm activity even further
west spreading into Southwest AZ if this easterly wave comes to
fruition.

Temperatures next week will moderate closer to mid-July normals
as moisture gradually increases and H5 heights aloft fluctuate
around 591 dam, near the climatological average for this time of
year. As such, the latest NBM shows the upcoming workweek starting
with continued lower desert highs in a 105-110 degree range,
dropping into a 103-108 degree range by midweek.

&&

.AVIATION...Updated at 1816Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
Gusty westerly winds will prevail through most of the day through
early tonight, with 20-25 kt gusts common and occasional gusts up
to 25-30 kt. Winds will be slow to weaken early tonight and
confidence of an easterly wind shift tomorrow morning is low and
thus represented with a VRB line at KPHX. Similar gustiness is
expected tomorrow. Skies will remain mostly clear with no
slantwise visibility impacts expected.

Southeast California/Southwest Arizona including KIPL and KBLH:
Daytime and evening breeziness is expected at both terminals with
mostly clear skies through the TAF period. The overall wind
pattern will follow the familiar diurnal trends with gusts upwards
of 20-25 kts in the afternoon at KBLH and during the early
evening hours at KIPL.

&&

.FIRE WEATHER...
Regionally dry conditions and above normal temperatures will
persist through the upcoming weekend, with lower deserts highs
reaching 108-116 degrees today and dropping to around 105-110
by Friday and through the weekend. MinRH values will range from
15-20% nearly every day, while MaxRH values will generally range
from 30-50%. One exception will be across Imperial and southern
Yuma Counties where periodic gulf surges will result in MaxRH
values in excess of 50-60%. An uptick in afternoon/evening
breeziness (gusts to 25-35 mph) today and lingering particularly
over the high terrain of the eastern districts Friday may lead to
locally elevated fire weather conditions. Otherwise, anticipate
typical diurnal wind trends with afternoon upslope gusts to 15-25
mph. Very minimal rain chances will exist through this weekend,
with activity focused mainly across the eastern and southeastern
third of AZ, with CWR <10%.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning until 8 PM MST this evening for AZZ530>556-
     559>562.

CA...Extreme Heat Warning until 8 PM PDT this evening for CAZ560>570.

&&

$$

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