048
FXUS65 KPSR 161931
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1231 PM MST Sun Aug 16 2026

.KEY MESSAGES....

- Temperatures will heat up several degrees above normal through
  the week, with lower desert highs climb above 110 degrees most
  days.

- Extreme Heat Warnings will be take effect Monday and continue
  through Friday, with widespread Major HeatRisk.

- Thunderstorm activity through the majority of the upcoming week
  will be mostly confined to the Arizona high terrain and
  southeast Arizona.

&&

.SHORT TERM /TODAY THROUGH TUESDAY/...
A weak shortwave trough moved through this morning, within the
southwest flow, and helped drive some virga showers across the
area. Midlevel water vapor shows dry air moving in on the back
side of this feature, which will continue to spread across the
area through tonight and add a dry subsident layer at and above
500mb heading into Monday. Convection this afternoon will mostly
be limited to the high terrain of northern and eastern AZ, with
relatively weak updrafts due to minimal instability. Heading into
Monday a low pressure feature slowly moving through Chihuahua, MX
looks to come just close enough to shift mid-level steering winds
to more of a NE component, albeit weak, across southeast AZ,
including the White Mtns. This change, in addition to slightly
better instability, may be enough for gusty outflow winds to move
west/southwest out of the White Mtns toward South-Central AZ in
the late afternoon and evening. All members of the latest HREF
show an outflow, of varying strength and timing, moving through
southern Gila, Pinal, and Maricopa counties Monday evening. A
trend of evening outflows into the lower deserts may continue
Tuesday (and beyond) as moisture and instability nudge up
slightly. Synoptically, mid-level steering winds become more
easterly across all of southern AZ Tuesday as the low pressure
feature drops southwest through Sonora, MX and the subtropical
anticyclone positions near/over the AZ-NM border.

Unseasonably hot and extreme temperatures will be the primary
sensible weather impact through the start of the workweek as high
pressure strengthens over the area through Monday. Current
objective analysis shows 500mb heights are around 594-595dam, but
will rise up to 596-597dam by Tuesday, which is at or above the
97th percentile of climatology for this time of the year. High
temperatures today will be around 1-3 degrees above daily
averages, with lower deserts reaching 105-109 degrees.
Temperatures then warm a few degrees into Monday and Tuesday,
increasing up to 4-6 degrees above averages and coming within a
few degrees of daily records. This does mean a return of
temperatures reaching or exceeding 110 degrees across the lower
deserts. These hot afternoon temperatures combined with early
morning lows in the mid 80s to 90 degrees will result in scattered
to widespread coverage of Major HeatRisk starting Monday, which is
when an Extreme Heat Warning will take effect.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/....
The subtropical high will remain entrenched across the region
through at least the end of the week, with 500 mb height fields
remaining steady between 595-597dam. Therefore, temperatures will
continue to run a good 4-7 degrees above normal as afternoon highs
across the lower deserts will range between 108-113 degrees.
There will also be little overnight relief as an increase in low-
level moisture will cause overnight lows to only bottom out
between the mid 80s to low 90s with the low 90s expected in the
Phoenix area. Therefore, widespread Major HeatRisk will continue
with Extreme Heat Warnings currently in effect through Friday
evening. Extension of this warning may be warranted through next
weekend as a weakening and slight re-positioning of the high
further away may not come until Sunday-Monday next week.

The latest guidance does show the high eventually moving
northeastward into the Four Corners region by the end of the week
into next weekend, putting the region under a more favorable
moisture advection pattern as the east to southeast flow
increases. Therefore, an increase in monsoonal activity is more
likely during this timeframe, mostly across the higher terrain
areas. Although, it will certainly be possible for convective
activity to impact the south-central AZ lower deserts at some
point as well, it is still too far out to know what days will be
most active as it will be dependent on mesoscale processes such
as outflow evolutions and/or any easterly waves, which are
difficult for models to resolve several days out. As of right
now, NBM PoPs across the south-central AZ lower deserts starting
next Thursday range between 10-30%.

&&

.AVIATION...Updated at 1720Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation weather concerns are anticipated through the period.
Winds will continue to exhibit diurnal tendencies, settling into
a W-NW direction this afternoon with speeds generally aob 8 kts.
The typical easterly shift will likely occur later than usual at
KPHX again tonight. Extended periods of light and vrb can also be
anticipated during the onset of any directional shifts. SCT-BKN
high clouds will progress over the region this afternoon before
clearing from W to E later this evening.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation weather concerns are expected at the SE California
terminals through the forecast period. Winds will fluctuate from
SE to W at KIPL and remain predominantly southerly at KBLH through
this evening with periods of light and vrb at both terminals
expected overnight and into early Monday morning. FEW high clouds
will gradually clear through this evening.

&&

.FIRE WEATHER...
Near to slightly above normal temperatures are expected this
afternoon and then will rise another few degrees into the coming
workweek. Most lower desert communities will reach or eclipse the
110 degree mark each day this week. Minimal monsoon activity is
expected through the first half of the week, with only a few
isolated thunderstorms expected across the far eastern districts.
Thunderstorm chances increase somewhat, mainly for south-central
AZ, by the latter half of the week as moisture increases.
Afternoon MinRHs through most of the week will 15-25% and
overnight recoveries will be around 35-50%, highest in the
Imperial Valley to Yuma, AZ. Outside of thunderstorm winds, the
overall winds will follow the typical diurnal tendencies with some
modest afternoon upslope gustiness.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning from 10 AM Monday to 8 PM MST Friday for
     AZZ530>544-546-548>551-553>555-559.

     Extreme Heat Warning from 10 AM Tuesday to 8 PM MST Friday for
     AZZ560.

CA...Extreme Heat Warning from 10 AM Monday to 8 PM PDT Friday for
     CAZ562-565>567-569-570.

&&

$$

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