254
FXUS65 KPSR 140506
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1005 PM MST Thu Aug 13 2026

.UPDATE...
Updated Aviation

&&

.KEY MESSAGES...

- Isolated showers and thunderstorms will remain possible mainly
during the afternoon hours today and Friday with the best chances
across the Lower Colorado River Valley.

- Near to below normal temperatures are forecast through Friday
before heating back up over the weekend into early next week.

- An Extreme Heat Watch has been issued for Maricopa and Pinal
counties for next Monday through Wednesday.

&&

.SHORT TERM /TODAY THROUGH FRIDAY/...
The upper level pattern remains mostly unchanged from this morning
with the upper level low over California, and the subtropical far to
the east in eastern Texas. With the low over CA southwesterly flow
has taken hold over the region with decent moisture being advected
into the Lower Colorado River Valley from tropical storms in the
Pacific. Current meso analysis shows PWATs near 1.5-1.6" along the
Lower Colorado, this moisture in conjunction with extra upper level
lift from the low to the west will lead to lingering chances (15-
20%) for isolated storms to develop later this evening. This is
supported within hi-res CAMs, highlighting storms developing along
the Lower Colorado River Valley into Southern Mohave County. For the
rest of the lower deserts chances for showers tonight are far more
limited, with a 10-15% chance of isolated showers possible, mostly
focused in the eastern portions of south central AZ and the higher
terrain areas. By Friday Shower and thunderstorm activity will
decrease further, as drier air will begin to scour out the current
moisture in the atmosphere.

Even though shower and thunderstorm activity will be decreasing
through today and Friday, the good news will be that afternoon high
temperatures will remain 4F-6F below normal through the rest of the
work week, thanks to the low remaining stationary over CA. This
translates to highs across the lower deserts between 96-103, and
widespread Minor HeatRisk. Morning lows will also be quite pleasant
Friday morning, ranging in the upper 70s to lower 80s.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
The weather pattern will shift over the weekend into early next week
as the subtropical ridge once again becomes the dominant weather
feature across the Southwestern U.S. The Pacific trough will
somewhat stick around into Saturday, but it is shown to quickly lift
to the north by Sunday as the ridge moves back in from the east.
Forecast H5 heights rise from 588-590dm on Friday to 591-594dm
Saturday before peaking around 594-596dm during the first half of
next week.

The dry air and increasing subsidence this weekend should keep all
but a few eastern Arizona high terrain showers and storms from
developing. Temperatures will warm up quickly over the weekend with
the expansion of the ridge with NBM forecast highs reaching 103-106
degrees Saturday and 106-109 degrees Sunday. The drop in moisture
will at least push surface dew points well into the 50s this weekend
to as low as the upper 40s early next week. This will help to keep
overnight lows close to normals through the weekend before we heat
up further next week. Ensembles eventually show the ridge center
shifting directly over Arizona by around Monday, likely staying in
place for a few days. The increased subsidence from the ridge with
no meaningful moisture return happening early next week should keep
lower desert PoPs below 10% to at most 10-20% over the far eastern
Arizona high terrain.

As the modestly strong (90-97th percentile of climatology) ridge
settles over Arizona during the first half of next week,
temperatures are likely to heat up enough to result in Major
HeatRisk across portions of the lower deserts. The highest
likelihood for Major HeatRisk looks to impact the Phoenix metro with
daytime highs around 110 degrees and lows around 90 degrees starting
Monday, but the more rural lower desert areas should experience
similar daytime highs as well. Due to the expectation of Major
HeatRisk, we have issued an Extreme Heat Watch for Maricopa County,
to include the Phoenix Metro, and Pinal County, valid from Monday
through Wednesday

&&

.AVIATION...Updated at 0505Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No major weather issues should exist through Friday evening under
periods of thicker mid/high cloud decks. Some variability may exist
in wind directions late evening before settling on an easterly
direction overnight. Similar variability may occur early Friday
afternoon before transitioning back to a westerly direction.
Confidence is good that TSRA/SHRA will remain well removed from PHX
terminals Friday.


Southeast California/Southwest Arizona including KIPL and KBLH:
Isolated TSRA Friday afternoon may impact SE California terminals
with direct impacts, however probabilities (~10%) are too remote to
include in this TAF package. The most likely effect will be gusty
outflow winds and potential abrupt wind shifts. Otherwise, winds
should oscillate between SW and SE with only occasionally stronger
gusts as thicker mid/high cloud decks remain common.

&&

.FIRE WEATHER...
Elevated humidity levels, below normal temperatures, and lingering
chances for showers and a few thunderstorms are expected today
before much drier air filters into the region Friday into the
weekend. Afternoon MinRHs of 30-50% today will drop to 20-30% by
Saturday and into the teens across the lower deserts starting
Sunday. Overnight recoveries will remain good to excellent. Winds
will remain predominately out of the south southwest much of the
period with overnight light easterly downsloping winds over the
eastern districts. Temperatures will warm back to normal by Saturday
and then above normal starting Sunday.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Watch from Monday morning through Wednesday evening
     for AZZ534-537>544-546-548>551-553>555-559.

CA...None.

&&

$$

SHORT TERM...Ryan
LONG TERM...Ryan/Kuhlman
AVIATION...18
FIRE WEATHER...Kuhlman