654
FXUS65 KPSR 252334
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
434 PM MST Tue Aug 25 2026

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

&&

.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 12Z PSR sounding provides further evidence that lower desert
storm chances are essentially out of the picture for today, with
mean low level mixing ratios below 9 g/kg and PWAT around 1.25". For
perspective, values around 10+ g/kg and 1.3-1.5+", respectively,
would be marginally supportive for formation and/or maintenance of
lower desert storms this time of year. However, enough moisture
combined with terrain-driven convergence will support chances for
isolated thunderstorms over prominent features like the Kofa Mtns,
and maybe some weak storms or just isolated convective showers over
portions of Southern Gila County. Also evident in the 12Z PSR
sounding is a more prominent midlevel inversion and warmer H5
temperatures compared to the same time yesterday, indicative of
increasing subsidence over the forecast area. This comes as the
subtropical high over Southern NM continues to expand westward,
increasing its influence over the Desert Southwest. RAP analyzed H5
heights around or just above 596 dam have now expanded to encompass
almost all of AZ. Ensembles remain in excellent agreement that H5
heights will peak between 595-598 dam over the forecast area and
remain fairly constant through Thursday as the subtropical high
centers itself over Southeast AZ/Southwest NM. NAEFS mean 850 mb
temperatures will increase to 29C-32C Wednesday and Thursday, above
the 99th percentile of climatology and near climatological maximum
values, supporting lower desert highs near 115F for the typically
hotter spots, challenging records in several spots (see Climate
section). As a result of the well above normal temperatures, and
overnight lows in the 80s to lower 90s providing little relief,
HeatRisk will solidly fall in the Major to Extreme category heading
through the rest of the week. Therefore, Extreme Heat Warnings will
remain in effect through the end of the week and even into the
weekend.

Moisture will remain meager through Thursday, with 1000-700 mb
mixing ratios between 6-8 g/kg and ensemble mean PWATs around 80% of
normal. More isolated, terrain-anchored thunderstorms are likely to
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.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Guidance continues to point towards the subtropical high shifting
east of the region starting Friday as a troughing pattern develops
over the Northwest US/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. 1000-700MB
mixing ratios are forecast to increase to 10-12 g/kg, enough to
support rain chances even over the lower deserts, with NBM/WPC
PoPs currently reflecting 20-30% chances across South-Central AZ.
This is a decent increase from previous runs but still several
days out, so models are still subject to change. Temperatures
are forecast to drop closer to late August normals by Sunday or
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 2328Z.

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

No aviation weather concerns under FEW-SCT mid/high level cloud
decks can be expected throughout the TAF period. The overall wind
pattern will continue to exhibit the typical diurnal tendencies
with overall speeds aob 10 kts. Periods of light variability are
likely, especially during the diurnal transitions.

Southeast California/Southwest Arizona including KIPL and KBLH:

No aviation weather concerns under FEW-SCT mid/high level cloud
decks can be expected throughout the TAF period. Winds will
generally oscillate between the west to southeast with overall
speeds ranging between 8-12 kts with the potential for some
modest gusts in the afternoon/early evening. An extended period of
light and variable winds is likely during the early morning hours.

&&

.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 midweek with gradual drying conditions. Afternoon minimum
humidities will mostly fall into the teens through the rest of the
week before improving this weekend. 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 25   113 in 2011    116 in 1962    117 in 1962
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...Whittock
LONG TERM...Whittock/Ryan
AVIATION...Lojero
FIRE WEATHER...Whittock/Ryan
CLIMATE...18/Kuhlman