573
FXUS65 KPSR 260842
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
142 AM MST Wed Aug 26 2026

.KEY MESSAGES...

- Extreme Heat Warnings remain in effect through Saturday across
  much of the area.

- Lower desert highs in excess of 110 degrees and overnight lows
  in the eighties to lower nineties will be common this week,
  resulting in Major to Extreme Heat Risk.

- Monsoon storm chances will be very limited before a pattern
  change occurs this weekend, which will result in an increase in
  moisture and promote temperatures dropping closer to late August
  normals by Sunday or early next week.

&&

.SHORT TERM /TODAY THROUGH THURSDAY/...
The subtropical ridge can been seen positioned along the AZ/NM
boarder advecting drier air into the lower deserts. The drier
conditions will to last through the end of the week, with
forecasted PWATs expected to fall near 1" in south central AZ and
even below 1" in the eastern high terrain by Wednesday. This is
accompanied by forecasted mixing ratios also falling to around 6-8
g/kg. However, some isolated, terrain-anchored thunderstorms may
develop each afternoon for the next few days before a pattern
change occurs heading into this weekend, drawing in better
moisture from over Sonora/the Gulf of California.

The more note worthy condition for this week will be the heat. H5
heights will peak Wednesday-Thursday with heights ranging between 595-
598 dam, or above the 99th percentile of climatology. Many areas
across the lower deserts will be flirting with record high
temperatures, with Phoenix showing around a 50% chance of at least
tying the record, and a 20% chance of surpassing the record high of
117F set in 2011 on Wednesday. Then on Thursday Phoenix has about
another 50% chance of tying and a 30% chance of surpassing the
record of 114F set in 2023. Needless to say this week is going to be
hot with the lower deserts region ranging between 112F-118F, and
very little relief with the overnight lows remaining in the upper
80s to lower 90s. Widespread Major to Extreme HeatRisk will continue
through the end of the week, as a result the Extreme Heat Warning
will also remain in effect through the end of the week and even into
the weekend. Ensure to stay hydrated and follow heat safety tips.
&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
The subtropical ridge is still expected to weaken and shift back
eastwards by Friday according to ensembles. This is due to a
troughing pattern pushing into the NW CONUS and along the West
Coast. As the trough pushes eastward, PWATs will begin to improve,
reaching near 1.5"-1.7" by Saturday and lasting through at least the
weekend. Mixing ratios will also significantly improve going from
mid week`s 6-8 g/kg to 10-12 g/kg by this weekend, generating better
support for storm formation in the lower deserts. With that being
said NBM/WPC continue to show PoPs over the weekend between 20-35%
across South-Central AZ, and now even up to 50% in the eastern high
terrain. WIth these PoPs the NBM/WPC QPE totals over the weekend are
forecasted between 0.10"-0.25" to locally higher in the higher
terrain areas. Continued monitoring of this system will be needed
but models continue to show support for activity developing this
weekend. In other good news, temperatures are forecast to drop
closer to late August normals by Sunday and into early next week as
falling midlevel heights and an increase in moisture/cloud cover
over the eastern CWA support a cooling trend (more pronounced across
South-Central AZ).

&&

.AVIATION...Updated at 0510Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:

No major aviation weather concerns under FEW-SCT mid/high cloud
decks can be expected throughout the TAF period. The overall wind
pattern will continue to exhibit the typical diurnal tendencies
with the easterly wind shift at KPHX likely around 12z. Heading
into early Wednesday evening, wind directions become highly
uncertain as there are indications from guidance of potentially a
couple of outflows from storm activity north and east of Phoenix
and across southeast AZ impacting the terminals with one outflow
from the northeast and another from the southeast. Confidence is
low of these outflows materializing and surviving into the
Phoenix area and thus have not been included in the latest TAF
package.

Southeast California/Southwest Arizona including KIPL and KBLH:

No major aviation weather concerns under FEW-SCT mid/high cloud
decks can be expected throughout the TAF period. Winds will mostly
oscillate between the southeast and west with overall speeds
ranging between 7-12 kts. An extended period of light and
variable winds will be common Wednesday morning.

&&

.FIRE WEATHER...
Hot and seasonally dry conditions will prevail for much of the
rest of the week. Strong high pressure will settle over the
region starting today with dry conditions continuing throughout
the workweek. Afternoon minimum humidities will mostly fall into
the teens through the rest of the week before improving back above
20% this weekend, except the western CA districts. Temperatures
will be around 5-10 degrees above normal, with lower desert highs
eclipsing 110 degrees nearly every afternoon through at least
Friday. Outside of distant thunderstorm outflows, expect overall
light winds (below 15 mph) following typical diurnal tendencies
with some modest afternoon upslope gustiness.

&&

.CLIMATE...
Record highs:

Date       Phoenix         Yuma         El Centro
----       -------         ----         ---------
Aug 26   117 in 2011    115 in 2020    115 in 1981
Aug 27   114 in 2023    120 in 1981    117 in 1981
Aug 28   117 in 2023    118 in 2023    117 in 2009
Aug 29   116 in 2023    117 in 1954    117 in 2005

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning until 8 PM MST Saturday for AZZ530>555-559-
     560.

     Extreme Heat Warning until 8 PM MST Friday for AZZ556-561-562.

CA...Extreme Heat Warning until 8 PM PDT Saturday for CAZ562-565>567-
     569-570.

     Extreme Heat Warning until 8 PM PDT Friday for CAZ561-563-564-
     568.

&&

$$

SHORT TERM...Ryan
LONG TERM...Whittock/Ryan
AVIATION...Lojero
FIRE WEATHER...Whittock/Ryan
CLIMATE...18/Kuhlman