646
FXUS65 KPSR 151814
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1114 AM MST Tue Jul 15 2025

.UPDATE...Updated 18Z Aviation Discussion.

&&

.KEY MESSAGES...

- Rain chances will improve over the next couple of days with the
  best chances over eastern Arizona and at least a 20-30 percent
  chance expanding into south-central Arizona Wednesday into
  Thursday.

- A few strong storms will be possible this afternoon and
  evening, likely focused east and southeast of the Phoenix area.

- After near normal temperatures today, expect slightly below
  normal temperatures with plenty of clouds Wednesday and
  Thursday.

&&

.SHORT TERM /Today through Wednesday/...
A complex forecast scenario this week continues to lead to fairly
low forecast confidence. The main issues involve discrepancies
between models with how much moisture and instability will be
available and the positioning and evolution of the upper level low
which has just developed over central Baja. The latest thinking
is today may present the best chance of a couple strong to
marginally severe storms, while Wednesday may now be less active
than previously expected. Moisture levels have increased since
yesterday and should continue to do so through tonight. Forecast
PWATs show readings between 1.4-1.6" later today focused over
south-central Arizona with MUCAPEs climbing to between 500-750
J/kg over much of the area to as high as 1000 J/kg across
southeast Arizona. Weak difluence aloft is also likely to develop,
while mid level winds (600-400mb) become slightly enhanced out of
the east up to 20 kts.

The latest Hi-Res CAMs show fairly good agreement with shower and
storm development by mid afternoon along the Mogollon Rim and much
of far southeast Arizona. The most vigorous convection is expected
across southeast Arizona with storm induced outflows likely
reaching Pinal Co. by early evening. Strong gusty outflow winds
may pose some risk of blowing dust southeast of Phoenix early this
evening, while additional storm development will be possible.
There may be enough instability leftover early this evening for a
strong thunderstorm or two across Pinal Co. It may then be
possible to get a decaying outflow into the Phoenix metro, but the
CAMs really do not show any strong winds. Guidance also suggests
the complex of storms over southeast Arizona is likely to induce
an MCV which may bring additional showers or a weak thunderstorms
during the overnight hours tonight as the MCV gradually lifts to
the north northwest through south-central Arizona.

If the MCV scenario comes to fruition, it now looks like it may
be a determent for additional shower and thunderstorm development
across south-central Arizona at least through Wednesday afternoon.
There is also model evidence of some drying already beginning to
take place across southwest Arizona to as far north and east as
the Phoenix area starting Wednesday morning. Because of these
potential negative factors, we have lowered PoPs for south-central
Arizona on Wednesday. Guidance does still suggest a good deal of
shower and weak thunderstorm activity over eastern Arizona on
Wednesday and any weak to modest outflows may be enough to help
trigger some activity into the lower deserts by Wednesday evening.
The potential for any strong storms Wednesday has been reduced
largely in part due to warming aloft and weakening instability.
Some higher terrain areas should still be able to see a few
heavier rain producing cells, but the overall risk for excessive
rainfall will be marginal at best.

&&

.LONG TERM /Thursday through Monday/...
Forecast confidence for later this week continues to be fairly low
as model differences remain. Both the GEFS and EPS show noticeable
drying occurring on Thursday, but the uncertainty lies in how
quickly we dry out. Models are finally mostly agreeing on bringing
the upper level low northward into northern Baja with potential
forced ascent still in place over much of Arizona. If there is
enough moisture left over, we may be able to see 500 J/kg or so of
MUCAPE during the afternoon hours, but that may not occur in a
large area as we are still likely to see considerable cloud cover.
Just like Wednesday, Thursday may mostly involve scattered
showers and weak storms over higher terrain areas with a few
isolated storms possible over the Arizona lower deserts.

The drying is expected to continue Friday into Saturday with
forecast PWATs dropping to between 1.1-1.3" Friday to around 1"
Saturday. Rain chances Friday may partially depend on the
eventual track of the upper level low which is mostly shown
tracking up the CO River Valley or across southern California
early on Friday. The eastern Arizona higher terrain should again
have afternoon chances for showers and thunderstorms Friday, but
we may also have a shot at some isolated convection closer to the
upper low, maybe across southwest Arizona. By Saturday, the upper
low is likely to have lifted far enough to the north or west that
it will become a non-factor on our weather. Enough lingering
moisture may still be present across eastern Arizona this weekend
for some afternoon scattered convection, but the south-central
Arizona lower deserts are likely to remain quiet.

Temperatures are expected to cool off a good deal during the
middle part of the week with below normal temperatures on
Wednesday and Thursday, especially across south-central and
eastern Arizona. As we stated yesterday, highs in the Phoenix area
on Thursday may struggle to reach 100 degrees. As we really begin
to dry out Friday into the weekend, temperatures will begin
creeping upward again with readings back into the normal range by
around Saturday. Temperatures at or just above normal are likely
to persist through early next week as the subtropical ridge is
likely to stay just to our east.

&&

.AVIATION...Updated at 1755Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
Current west winds will increase up 10-15 kts this afternoon and
evening with gusts up to 20-25 kts. Confidence in wind directions
lowers heading into the late evening hours, but a southerly to
southeasterly shift is favored by around 04-06Z. This wind shift
is expected to be assisted by an outflow boundary. The outflow
boundary is expected to weaken as it moves across the Phoenix
Metro, with gusts into the 20s expected at KIWA and gusts up
around 20 kt possible at KPHX (a TEMPO group has been added to
the KPHX TAF for this). Afternoon and evening storms are expected
to stay east to south of Phoenix. There is a slight chance
(10-20%) for a light shower tonight-tomorrow morning and an even
lower chance of a flash of lightning. Convective cloud bases will
be as low as 8-10K ft AGL this afternoon through tomorrow morning,
with SCT to BKN coverage at times.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation weather concerns under mostly clear skies can be
expected throughout the TAF period. Winds will generally be out of
southeast at KIPL and out of the south at KBLH. Wind gusts upwards
of 20-25 kts will be expected at times during the afternoon and
evening.

&&

.FIRE WEATHER...
Moisture will gradually increase across much of Arizona over the
next couple of days providing increased chances for showers and
thunderstorms focused across higher terrain areas. Temperatures
will drop off from near normal today to below normal Wednesday
and Thursday. Afternoon MinRHs will improve with readings around
20% today and 25% Wednesday and Thursday. Expect south
southwesterly gusts of 20-30 mph at times over the CO River
Valley with more diurnal lighter winds over the eastern districts.
Some drying conditions will begin to usher back into the area
later this week resulting in more limited shower and thunderstorm
chances by Friday. 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...Kuhlman
LONG TERM...Kuhlman
AVIATION...Berislavich/Benedict
FIRE WEATHER...Kuhlman