375
FXUS65 KPSR 062310
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
410 PM MST Fri Jun 6 2025


.UPDATE...Updated 00z Aviation Discussion...

&&


.DISCUSSION...

KEY MESSAGES:

- Dry conditions with temperatures peaking around 10 degrees above
normal early next week

- Widespread moderate HeatRisk during the first half of next week
relaxing later in the week

Early afternoon WV imagery depicts an elongated, positively tilted
trough extending from the northern plains to the central California
coast with several smaller scale vorticity centers captured within
the flow pattern. Meanwhile, high amplitude ridging and a blocking
type pattern characterizes the East Pacific synoptic flow with a
tendency for northern stream features to remain progressive, but
southern stream features to be retrogressive. As such, confidence is
excellent that the southwestern PV anomaly of the aforementioned
trough will detach, retrograde, and become part of a temporary Rex
block settling over the East Pacific and North American west coast
this weekend. Concurrently, subtropical ridging over south
Texas/northern Mexico will attempt to build into the SW Conus
battling against the influence of the southern stream trough
comprising the base of the Rex block. This pattern configuration
will conspire to yield warming and drying weather conditions through
the first half of next week.

Any lingering moisture was quickly becoming eroded from the region
today under deep SW flow as objective analysis suggests boundary
layer mixing ratios falling below 6 g/kg (and verified by in situ
surface dewpoints tumbling near 40F) resulting in little more than
scattered deep afternoon cumulus over higher terrain areas. With
ridging building into the region, H5 heights in a 584-588dm range
today will increase closer to a 586-590dm range early next week.
Narrow guidance spread increases forecast confidence of warming
temperatures peaking up to 10F above the daily normal Sunday and
Monday. NBM probabilities of reaching 110F in a 30-70% range are
mostly focused over lower deserts of SE California, however it would
not be surprising for some of the warmest locations around the
Phoenix metro to touch this threshold as well. Nevertheless,
widespread moderate HeatRisk will be common for most lower elevation
population centers through the middle of next week.

East Pacific blocking will gradually deteriorate early next week
becoming marginally progressive while losing amplitude migrating
downstream. The flat basal troughing forming the southern extent of
the block will act to dampen subtropical ridging with modest height
falls impacting the CWA towards the middle of the week. Forecast
uncertainty is somewhat larger during this time frame dependent on
the depth of the weak PV anomaly and ability to carve away higher
midtropospheric heights. Regardless, temperatures should remain in a
slightly above normal range, yet retreating from the peak warmth.
Late in the week, ensemble suites remain in good agreement bringing
more pronounced negative height anomalies into the Pacific NW and
Great Basin acting to further dampen heights across the SW Conus.
However, ensemble spread begins to grow with a notable number of
GEFS members (and lower percentage of CMC and EC members)
maintaining a stronger northern Mexico subtropical ridge limiting
the magnitude of heights falls locally. Thus, while ensemble means
have discernible height falls across the region with temperatures
cooling back to a near normal range, the eventual outcome may result
in somewhat less cooling and only a brief respite before returning
to an above normal level beyond next weekend.

&&

.AVIATION...Updated at 2310Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
No aviation weather concerns under clear skies are expected
throughout the TAF period. The overall wind pattern will continue
to exhibit the typical diurnal tendency with speeds aob 10 kts.
Periods of light and variable winds are likely as well.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation weather concerns under clear skies are expected
throughout the TAF period. Winds at KIPL will fluctuate between
the E-SE and winds at KBLH will fluctuate between the SE-SSW.
Overall wind speeds will remain aob 10 kts.

&&

.FIRE WEATHER...
Warming temperatures with readings climbing around 10F above normal
will affect the districts through the middle of next week while the
environment becomes progressively drier. Afternoon MinRHs will
largely fall near 10% with more prevalent single digit RH`s Sunday
and Monday. This will follow primarily poor to fair overnight
recovery of 20-40%. Winds should follow fairly typical late spring
cycles with periods afternoon upslope gustiness. Somewhat more
breezy conditions may arrive to the region towards the end of next
week resulting in a slightly elevated fire danger.

&&

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

$$

DISCUSSION...18
AVIATION...Lojero
FIRE WEATHER...Ryan/18