737
FXUS65 KPSR 112328
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
428 PM MST Wed Jun 11 2025

.UPDATE...Updated 00Z Aviation Discussion.

&&

.KEY MESSAGES...

- Dry conditions with temperatures remaining 3 to 5 degrees above
  average across the region through Friday.

- A strong ridge of high pressure will build over the Desert Southwest
  this weekend, promoting the hottest temperatures of the year
  thus far.

- An Extreme Heat Watch is in effect from Saturday morning through
  Monday evening for high temperatures ranging from 106 to 115
  degrees across the lower deserts.

&&

.DISCUSSION...
Extreme heat will become the main weather concern by this weekend as
temperatures reach their highest levels of the year so far. Today we
will continue to see temperatures right around 3 to 5 degrees above
average across the region as a broad upper lvl ridge sits off the
coast of the Baja California. Our forecast area will remain under
the influence of this ridge over the next few days as it continues
to slowly migrate ewd. As this shift in the ridge occurs, 500 mb
heights will range from 588-592 dam or near the 90th percentile
of climatology, resulting in high temperatures remaining steady
around 104-108 degrees through Friday.

Heading into this weekend, ensembles (GEFS and EPS) are still in
excellent agreement that the afomentioned upper lvl ridge will
continue to build and strengthen over the Desert Southwest and
reposition over the AZ/NM border by Saturday. Over the weekend,
500 mb heights within the center of the ridge are projected to
reach 595- 595 dam with 592-594 dam heights overspreading our
entire forecast area. These heights are around the 95th percentile
of climatology for mid June. Along with the increasing
heights/thicknesses, 850 mb temperatures will rise to around
27-30C on Saturday and 28-32C on Sunday and Monday which would
equate to surface temperatures of 108- 111F on Saturday and
110-115F on Sunday and Monday across the lower deserts. The
chances for tying the record high of 115F at Sky Harbor is now 30%
on Sunday and 20% on Monday. Temperatures of this magnitude will
result in areas of Major HeatRisk with the most widespread Major
HeatRisk occurring on Sunday. Make sure to follow heat safety
guidance this weekend by limiting time spent outdoors to the early
morning or evening hours and staying hydrated.

There is still a high degree of uncertainty regarding the arrival of
a shortwave trough on Tuesday which could potentially result in
cooler temperatures across the region. The magnitude of cooling will
greatly depend on the depth and positioning of this trough as some
model members are depicting a weaker and faster solution (EPS) and
others (GEFS) are suggesting slower and deeper trough which would
foster cooler temperatures. Right now NBM highs on Tuesday are
ranging from 104-108 degrees which would indicate a break in the
extreme heat conditions at least through the middle of next week.
The trough on Tuesday could bring an uptick in winds, especially to
the higher terrain areas of southcentral AZ where gusts could reach
20-30 mph, however our forecast area looks to remain dry.

&&

.AVIATION...Updated at 2328Z.

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

No major aviation weather concerns are expected through the TAF
period. Winds continue to exhibit diurnal tendencies and will
continue to gust for the next few hours but look to relax late
this evening into the overnight hours. Out west at KBLH gusty
conditions will return with speeds generally between 20-25kts but
could see period near 30kts. FEW high clouds will persist at all
terminals.

&&

.FIRE WEATHER...
Above normal temperatures and dry conditions will prevail through
the remainder of this week. Winds will continue to follow typical
diurnal tendencies with periods of modest afternoon upslope
breeziness (gusts of 20-25 mph at times). Minimum humidity will
bottom out between 10-15% over the next few days with poor to fair
overnight recovery between 20-50% region-wide. Temperatures are
forecast to spike well above normal this upcoming weekend with
afternoon highs reaching 110 or hotter as early as Saturday across
the lower deserts as Min RHs lower in the 5-10% range. By early
next week, the arrival of a dry weather system may result in an
uptick in winds across southeast CA and the higher terrain areas
of southcentral AZ. These gusty winds combined with dry fuels and
very low humidity could result in elevated fire weather concerns.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Watch from Saturday morning through Monday evening
     for AZZ530>544-546>556-559>562.

CA...Extreme Heat Watch from Saturday morning through Monday evening
     for CAZ562>567-569-570.

&&

$$

DISCUSSION...Salerno
AVIATION...Ryan
FIRE WEATHER...Salerno/Kuhlman