San Tan Valley, Arizona 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

238
FXUS65 KPSR 130948
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
248 AM MST Wed Aug 13 2025

.KEY MESSAGES...

- Areas of Major HeatRisk with Extreme Heat Warnings remain in
  effect through early this evening for portions of the central
  AZ lower deserts, the Lower Colorado River Valley, and Imperial
  Valley.

- Today will bring increased chances for showers and storms over
  the eastern Arizona high terrain with potential for isolated
  storms and even a higher likelihood of gusty storm outflow winds
  and patchy blowing dust affecting the south-central Arizona
  lower deserts.

- Chances for showers and thunderstorms will continue for Thursday
  and Friday with temperatures gradually cooling back into the
  normal range by Friday.

&&

.SHORT TERM /Today/...
Moisture continues to slowly increase across southern and central
Arizona, but today still looks to be drier than we typically see
for a typical monsoon day. PWATs are forecast to climb to between
1.1-1.2" across much of southern Arizona by this afternoon with a
slight improvement closer to 9 g/kg for mixing ratios. Given the
hot conditions and highs reaching between 108-112 degrees this
afternoon, the moisture should be enough for at least scattered
convection over the higher terrain. The 00Z HREF shows storms
developing along the Mogollon Rim and over southeast Arizona mid
to late afternoon.

Guidance also shows some indication of mid-level enhanced
easterly winds setting up across eastern Arizona which may help to
sustain some of the convection and push it into the lower
deserts. If this happens, much of the convection is likely to
dissipate as it reaches the lower deserts due to the limited
moisture. However, Hi-res CAMs also show colliding outflows over
or around Phoenix which may lead to some short-lived pulse-type
thunderstorms. Given the drier environment, localized strong to
near severe winds could be a problem today as the 00Z HREF shows
10% probability of 50 kts over southern Gila County and over
western/central Pima County. Strong outflow winds and localized
strong downdraft winds from the isolated pulse thunderstorms may
also bring wind gusts greater than 35 mph (30-40% probability)
into the lower deserts. PoPs have increased today to 15-20% for
the Phoenix area to 30-40% across the higher terrain.

&&

.LONG TERM /Thursday through Tuesday/...
By Thursday the subtropical ridge center is forecast to shift to
the east reaching northern New Mexico, while a Pacific trough
moves into California. This shift in the flow pattern is expected
to allow for southerly moist flow to set up over much of Arizona
increasing PWATs to between 1.2-1.4" on Thursday and 1.3-1.5" on
Friday. Unfortunately, model uncertainty remains quite high for
rainfall potential as cloud cover may begin to limit instability
and the steering flow increases out of the southwest due to the
incoming trough. The trough should at least provide for some
larger scale lift Thursday into Friday, but it looks to be fairly
weak forcing. Convective potential on Thursday is also likely
going to be depend on what happens with the storm activity later
today. If convection today is widespread and impacts the south-
central Arizona lower deserts, then Thursday may see more limited
activity. If today isn`t very active, then chances Thursday should
be better. NBM PoPs for Thursday still seem too optimistic, so we
have lowered PoPs to 20-40% over the lower deserts to around 50%
over the higher terrain. Given the increased moisture on Thursday,
a few storms could become strong if we realize enough sunshine to
destabilize the lower levels of the atmosphere.

Guidance is still showing the best moisture occurring on Friday
with low level mixing ratios increasing to 10-12 g/kg, but as
with Thursday the amount of cloud cover may hinder our convective
potential. The flow pattern should also become more dominated by
the trough to our west as the subtropical ridge shifts even
farther to the east over Kansas and Oklahoma. Right now guidance
holds off any dry air advection into our area until Friday night
into Saturday, so unless things change we should have ample
moisture for shower and thunderstorm activity on Friday. As a
result, the NBM paints the highest PoPs for our area Friday
afternoon and evening. Even with the better moisture, it is still
far from being really juicy as there will remain a good deal of
dry air aloft. However, both the GFS and the Euro show good
(1000-1500 J/kg) MUCAPE for Friday afternoon likely with the help
of the cooler air aloft associated with the nearby trough. We will
have to keep an eye on the severe storm potential for Friday.

Drier air is then expected to spread across the region from west
to east beginning Saturday as the trough finally begins to push
the moisture to the east. We may be able to squeeze out a few
showers and storms on Saturday, but chances will mainly be
confined to the eastern Arizona high terrain. By Sunday,
conditions should be dry enough to eliminate any chances over the
lower deserts with at most 10-20% PoPs over eastern Arizona.
Similar low rain chances are expected for Monday before we
potentially see some moisture beginning to return by next Tuesday
or Wednesday.

Cooling temperatures will also be seen across the region later
this week as the trough lowers heights, moisture increases, and
cloud cover becomes a factor. NBM guidance shows highs dropping
to between 102-106 degrees across the lower deserts by Friday.
These near normal temperatures may persist into Sunday before we
start to warm again early next week.

&&

.AVIATION...Updated at 0545Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Uncertainty regarding outflow winds and periods of reduced
slantwise visibilities will be the primary weather issues through
tomorrow evening under a few mid/high cloud decks. West winds will
subside going into the overnight hours with typical diurnal
tendencies settling in over the next several hours. Lofted
wildfire smoke may continue to affect slantwise visibilities
throughout the period, especially at sunrise and sunset, but no
surface restrictions are expected. Winds shifting out of the
westerly direction will begin in the late morning and early
afternoon hours once again tomorrow, with occasional gusts 15-20
kts. Better chances of gusty outflow winds will be possible
tomorrow evening, currently best chances around 30-50% of 35+ mph
gusts between 01-04z out of the easterly direction. Thus,
reflected this potential with an earlier than normal shift out of
the east, with the main uncertainty being the timing and exactly
which direction (NE versus SE) and how strong the winds will be
with any outflow that reaches any terminal. Shower and
thunderstorm chances remain too low (<15%) to introduce any
VCSH/VCTS conditions at this time.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major weather issues will exist through tomorrow evening under
mostly clear skies. Winds will follow a near persistence forecast
with directions varying between SE and SW and gusts around 25kt
common at KBLH.

&&

.FIRE WEATHER...
A more active monsoon weather pattern is expected over the next
few days as moisture increases and temperatures begin to cool.
Storm activity today should be more concentrated over the Arizona
higher terrain, but there should also be some isolated evening
storms and gusty outflow winds into the lower deserts. Better
moisture for Thursday and Friday will result in continued
rain chances across much of the eastern districts with wetting
rainfall chances as high as 30-40% for the eastern districts.
Minimum afternoon humidity levels will mostly range between 15-25%
with fair to good overnight recoveries. Outside areas of
thunderstorms, winds will continue to follow diurnal trends with
afternoon gusts up to 15-20 mph. Drier air will eventually usher
back into the area over the weekend mostly ending rain chances
except for far eastern Arizona. MinRHs will eventually lower to
closer to 10-15% by next Monday.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning until 8 PM MST this evening for AZZ530-532-
     534-537>544-546-548>551-553>555-559.

     Blowing Dust Advisory from 5 PM this afternoon to 9 PM MST this
     evening for AZZ553.

CA...Extreme Heat Warning until 8 PM PDT this evening for CAZ562-563-
     566-567-569-570.

&&

$$

SHORT TERM...Kuhlman
LONG TERM...Kuhlman
AVIATION...Young
FIRE WEATHER...Kuhlman