304
FXUS65 KPSR 102246
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
346 PM MST Tue Jun 10 2025

.KEY MESSAGES...

- Dry conditions with temperatures remaining 3 to 5 degrees above
  average across the lower deserts through the rest of this week

- A strengthening ridge of high pressure over the Desert Southwest
  this weekend will promote the hottest temperatures of the year
  thus far.

- An Extreme Heat Watch is in effect from Saturday morning Monday
  evening for high temperatures ranging from 106 to 114 degrees
  across the lower deserts.

.DISCUSSION...

Afternoon mid-lvl water vapor imagery depicts a shortwave trough
passing through NM and West TX while an anomalously strong ridge
sits off the coast of SoCal. Our forecast area remains between both
of these features which will continue to promote dry northwesterly
flow aloft. Temperatures have been steadily climbing into the low
100s and should again top out a few degrees above normal this
afternoon. Another quiet night is anticipated region-wide with lows
settling in the low to mid 70s with the exception of central Phoenix
where lows will be slightly warmer in the lower 80s.

As we continue through this week, ridging over the E Pacific will
slowly migrate westward into N Mexico, keeping our area under
quasi-zonal flow. This pattern will result in very little day-to-
day change in temperatures with highs remaining mostly steady in
the 100-108 degree range across the lower deserts and mid 90s in
the higher terrain through Friday. These above normal temperatures
will result in a widespread Moderate HeatRisk. Therefore it is
important to continue to practice heat safety measures by taking
frequent breaks if working outdoors and consuming plenty of water.

By this weekend, there is still very good consensus amongst
ensemble guidance that the ridge over N MX will build northward
and strengthen over the Desert Southwest. This will result in
increasing 500 mb hghts to around 594-596 dam causing temperatures
to soar to near record levels. In light of the concern for impactful
heat as well as HeatRisk increasing to locally Major, an Extreme
Heat Watch has been issued for much southeast CA, southwest AZ,
and southcentral AZ from Saturday morning through Monday evening
for high temperatures between 104-114 degrees.

The spread in high temperatures (NBM 25th-75th percentile) diverges
greatly from Tuesday onwards as some ensemble and deterministic
members indicate the potential for a shortwave trough to pass
through our region. If this were to come to fruition, temperatures
may cool by a few degrees heading into the middle of next week.
However, the magnitude and degree of cooling is still uncertain at
this time.


.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 upwards of 20 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.

&&

.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...Smith/Berislavich
FIRE WEATHER...Young/Salerno