San Tan Valley, Arizona 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

286
FXUS65 KPSR 142114
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
214 PM MST Mon Jul 14 2025

.UPDATE...Updated Short Term & Fire Weather Discussions.

&&

.KEY MESSAGES...

- Near to slightly above normal temperatures will last into
  Tuesday before dropping to slightly below normal later in the
  week.

- Rain chances will gradually improve over the next couple of
  days, initially confined to higher terrain areas today before
  descending into the lower deserts as early as Tuesday evening.

- Active monsoon weather is expected for Wednesday and Thursday
  across southern and central Arizona with strong winds and
  localized heavy rainfall and minor flooding all possible.

&&

.SHORT TERM /Rest of Today and Tonight/...
Mid-level water vapor satellite imagery reveals a subtropical high
still west of our region, over the Pacific Ocean, but portions of
it stretching back into the Great Basin and northern and western
AZ. PWAT values have been increasing across southern and eastern
AZ today. With the increase in moisture, most of the shower and
thunderstorm activity this afternoon and evening will be confined
to southeastern and eastern portions of AZ. Early this afternoon,
some showers and storms have already started to develop across the
Mogollon Rim, White Mountains, and east of Tucson. There remains
a 10-20% chance of a few showers and/or thunderstorms reaching
into central and northern Pinal County and far eastern portions of
the Phoenix Metro. Highs today will reach into the 105-112 degree
range across the lower deserts and mid-to-upper 90s and near 100
degrees in the higher terrain. With overnight lows very similar to
this morning, with lows in the 80s across the lower deserts and
70s in the higher terrain. There will be a decent Gulf moisture
surge into our area this evening, which will help set the stage
for a more active monsoon day tomorrow.

&&

.LONG TERM /Tuesday through Sunday/...
The weather pattern will become more favorable for monsoon
conditions starting Tuesday as the subtropical high splits with a
new (fairly weak) center forming over northern Arizona.
Additionally, the weak trough to our south will start to become
more organized with a closed low forming in the upper levels
somewhere just off the coast of central Baja. The recentering of
the high will allow for the flow in the low and mid levels to turn
more out of the south and southeast, advecting better quality
moisture northward into Arizona.

PWATs later on Tuesday are forecast to rise to between 1.3-1.5"
into south-central Arizona, but low level mixing ratios are still
likely to be a bit on the lower side at around 9 g/kg. The latest
HREF and the 06Z HRRR do show isolated to scattered thunderstorm
activity across southeast Arizona northward into southern portions
of the Mogollon Rim Tuesday afternoon. The better moisture should
result in MUCAPE of upwards of 500-1000 J/kg, while we also may
begin to see some weak difluence aloft from the developing upper
low to our southwest. NBM PoPs seem reasonable calling for 50%
chances across the higher terrain with 20-40% chances extending
into the south-central Arizona lower deserts. However, the lower
deserts are still likely to have to contend with some CIN, so an
organized outflow or a collision of outflows is likely to be
needed for development over the lower deserts. The main threats
with any stronger storms Tuesday should be strong wind gusts of
35-45 mph, while blowing dust may also end up being an issue if
any organized strong outflows form.

Wednesday into Wednesday night may represent our best chances for
more widespread showers and thunderstorms as guidance shows the
best difluence aloft setting up over Arizona. Moisture levels
should also increase further during this time with PWATs reaching
anywhere from 1.4-1.7" and low level mixing ratios closer to 11
g/kg. Despite the better moisture, instability may be an issue as
forecast MUCAPEs may struggle to break 1000 J/kg due to increased
cloud cover and decreasing lapse rates. This may limit the threat
for stronger thunderstorms, but the improving forced ascent from
the upper level low`s influence should increase the overall
coverage of showers and thunderstorms starting Wednesday afternoon
and lasting into early Thursday. NBM PoPs increase to 40-60% over
the Phoenix area with 20-30% PoPs extending as far west as La Paz
and Yuma Counties. Even higher PoPs of 60-80% are seen over the
eastern Arizona higher terrain. Given the better moisture, the
potential for heavy rainfall is expected to increase starting
Wednesday afternoon with WPC highlighting all of south-central and
eastern Arizona in a Marginal Risk of excessive rainfall.
However, forecast QPF still seems to be on the low side with
averages of 0.1-0.3" over the lower deserts to 0.3-0.5" in higher
terrain areas. Localized higher amounts are sure to occur with
some areas likely seeing over an inch.

Model guidance is still unsure on how to handle the ejection of
the upper level low and how quickly drier air will spread
northeastward into the region. Models have essentially flip-
flopped from last night with the GEFS now the drier and faster
progressing model, while the EPS is slower with the low ejection
and keeps better moisture over our area through all of Thursday.
Forecast confidence for rain chances for Thursday is fairly low as
it will likely be contingent on how much the atmosphere is worked
over from Wednesday`s activity and how quickly to low lifts
northward. The NBM is keeping fairly high PoPs of 30-60% on
Thursday and this may be fine if moisture sticks around, but with
lowering instability potential rainfall amounts are likely to be
decreasing. Diminishing rain chances are expected Friday into
Saturday with both models finally agreeing on drier air working
into the area.

As far as temperatures for the rest of the week, the increasing
moisture, cloud cover, and lower heights aloft will all help to
drop daily highs to around or even slightly below normal for
Wednesday and Thursday. In fact, highs on Thursday in the Phoenix
area may not even reach 100 degrees if we see rain in the morning
and considerable cloud cover through the rest of the afternoon.
Temperatures should begin to warm back up by the weekend with
highs back to around normal. The subtropical ridge is then likely
to rebuild over the Southern Plains by early next week which
should in turn raise temperatures a bit higher over our region.

&&

.AVIATION...Updated at 1737Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
Gusts and elevated wind speeds will be the main aviation concern
through the TAF period. Gusts will resume this afternoon with
speeds generally around 20kts. A brief lull in winds is
anticipated this evening, but a relatively strong gulf surge will
lead to a period with winds around 15 kts with potential for gusts
between 20-25 kts from 05-09Z. Thunderstorm activity is expected
to stay well east of Phoenix today, with easterly outflow winds
not expected to reach terminals. FEW to SCT at or above 16K ft AGL
expected this evening/tonight. Slantwise visibility impacts
remain possible this morning and evening with lofted wildfire
smoke.

Southeast California/Southwest Arizona including KIPL and KBLH:
Periods of lofted smoke creating slantwise visibility issues will
continue to be the main aviation impact through this evening, with
those issues enhanced during the sunrise and sunset periods. KIPL
will primarily be out of the SE, with wind speeds expected to
increase into the low teens by this evening, lasting through the
overnight period, but look to relax by sunrise. KBLH will develop
gusts around 25kt this afternoon, and sustained wind speeds will
generally remain in the upper teens. Mostly clear skies through
the TAF period.

&&

.FIRE WEATHER...
Moisture will gradually increase across Arizona through the
middle part of the week providing increasing chances for showers
and thunderstorms, especially by Wednesday. Temperatures will drop
off from slightly above normal today and tomorrow to below normal
Wednesday and Thursday. Afternoon MinRHs should bottom out around
15% today with southwesterly gusts of 20-25 mph at times
continuing into the evening. RHs will improve Tuesday into
Wednesday with MinRHs between 20-30% as chances for rain
increase. Rain chances should mostly be confined to the eastern
Arizona high terrain through Tuesday before moving into the lower
deserts by Wednesday. Good chances for showers and thunderstorms
across south-central and eastern Arizona are likely to last into
Thursday before drying begins from the southwest. Eventually, high
pressure is likely to return to the region by the weekend with
RHs dropping back into the teens, temperatures returning to near
normal, and rain chances ending for all but the higher terrain.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$

SHORT TERM...Berislavich
LONG TERM...Kuhlman
AVIATION...Ryan/Benedict
FIRE WEATHER...Berislavich/Kuhlman