291
FXUS65 KPSR 052338
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
438 PM MST Thu Jun 5 2025

.UPDATE...Updated Aviation Discussion.

&&

.DISCUSSION...

KEY MESSAGES:

- Remote chance of an isolated shower or thunderstorm this
  afternoon over Joshua Tree National Park

- Hot and dry conditions are expected to increase into next week
  with lower desert temperatures peaking around 110 degrees on
  Sunday and Monday

- Widespread areas of Moderate HeatRisk expected Sunday and Monday

Early afternoon satellite WV imagery shows weak troughing centered
near the southern California coast that is acting to advect drier
air into the region. This drying trend is more prevalent across
southeastern portions of Arizona, while better moisture remains
in place across western portions of the state. According to the
latest SPC mesoanalysis, PWAT values range anywhere from 0.5"
across far eastern portions of the CWA to around 1.1" across
southeast California to the Lower Colorado River Valley. Given the
better moisture in the aforementioned areas, HREF guidance
supports continued higher instability values in these areas for
this afternoon with CAPE values as high as 500-1000 J/kg. Despite
the continued anomalous moisture and instability and lack of
inhibition, hi-res guidance show little support for any showers
and thunderstorms developing across southeast California this
afternoon with the lack of upper level support. Nonetheless,
can`t rule out an isolated orographically forced shower or
thunderstorm over places such as Joshua Tree National Park given
the favorable profiles. Any thunderstorm that were to develop
would be capable of producing gusty winds.

Drier air will continue to work its way into the region going
into this weekend and will put an end to any rain chances around
the area. Meanwhile, the subtropical ridge of high pressure
currently centered near the northern Mexico/southern Texas
international border will begin nudging its influence into our
area this weekend into early next week as it retrogrades westward
before becoming centered off the coast of the Baja Peninsula.
Operational and ensemble guidance show 500 mb heights climbing
upwards of 590-593 dm Sunday into Monday. Temperatures will
respond with forecast highs approaching or reaching 110 degrees
Sunday before peaking Monday. The latest deterministic NBM now
shows Phoenix reaching 110 degrees on Monday, while some warmer
locations such as El Centro may top out around 112 degrees. While
these forecast highs are about 7-10 degrees above normal for this
time of year, they are expected to fall short of any daily record
highs.

The hot temperatures will lead to increasing widespread Moderate
HeatRisk, and perhaps locally Major HeatRisk across parts of
southeast California, Sunday and Monday. Thus, folks and those
particularly sensitive to heat should exercise the necessary heat
safety measures to avoid heat-related illnesses. Heights aloft
will then begin to gradually lower going into the middle part of
next week. Ensemble clusters then show a larger trough moving into
the Pacific Northwest going into the latter part of next week.
This will help to further lower our heights locally and lead to a
gradual downtrend in temperatures. Dry conditions will prevail for
next week under this pattern.

&&

.AVIATION...Updated at 2338Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
No major weather issues should exist through Friday evening with
prevailing SKC sky conditions. W/SW winds will prevail this
evening followed by moderate confidence that the overnight E shift
will be later than is usual, and revision back to W slightly
earlier Friday (17-18Z). There will likely be some light
variabilty again during the diurnal W shift Friday. Wind speeds
will generally stay at or below 8 kts.


Southeast California/Southwest Arizona including KIPL and KBLH:
No significant weather concerns will exist through Friday evening
with prevailing SKC sky conditions. S/SE wind directions will be
favored through the period with some variability and brief SW
directional shifts possible. Confidence is good that speeds will
primarily remain below 10kt, however could increase closer to 15kt
at times.


&&

.FIRE WEATHER...
Drying conditions and hotter temperatures are expected into the
weekend. Afternoon MinRHs will decrease from 15-25% today to
7-12% by Saturday as lower desert high temperatures increase into
the lower triple digits, which is near normal for this time of
year. Overnight RHs will also decrease from 30-45% tonight to
25-35% Friday night for most places. Winds should follow fairly
typical diurnal tendencies with periodic afternoon upslope
gustiness. The dry weather pattern is expected to continue into
early next week with temperatures running 5-10 degrees above
normal and daily MinRHs mostly in a 5-10% range.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$

DISCUSSION...Smith
AVIATION...Benedict/18
FIRE WEATHER...Smith/Kuhlman