499
FXUS65 KPSR 091801
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1101 AM MST Sun Aug 9 2026

.UPDATE...18Z Aviation Discussion

&&

.KEY MESSAGES...

- Extreme Heat Warnings remain in effect through this evening as
  afternoon high temperatures approach the 110 degree mark across
  most of the lower desert communities, resulting in areas of
  Major HeatRisk.

- Shower and thunderstorm activity will once again develop across the
  higher terrain areas as well as across southern Arizona later
  this afternoon, with additional activity possible across the
  lower deserts this evening.

- Deeper moisture will provide a better opportunity for more widespread
  shower and thunderstorm activity during the first half of the
  week, along with cooler temperatures.

&&

.SHORT TERM /Today through Monday/...
Current objective analysis depicts the subtropical high centered
near the Four Corners Region with the region situated under modest
easterly flow of around 15-20 kts along the southern periphery of
the high. Similar to the last several days, thunderstorms are
expected to develop later this afternoon across the Mogollon Rim
and White Mountains and then migrate westward into south-central
AZ, with the likelihood of another storm complex developing across
southern AZ, especially in Pima County according to the latest
hi-res guidance. With DCAPE values expected to exceed 1500 J/KG,
there is a high potential of strong outflows to materialize and
affect the lower deserts with gusty winds exceeding 30-40 mph
along with areas of blowing dust, especially with the southern
outflow from the storm activity that develops in southern AZ.
Forecast soundings for this evening does still show a decent
amount of convective inhibition and thus it will take a strong
outflow/multiple outflow collisions to overcome this convective
inhibition to spark thunderstorms across portions of the south-
central AZ lower deserts, including the Phoenix Metro. This
scenario is being depicted by some of the hi-res guidance and
thus NBM PoPs for this evening across the south-central AZ lower
deserts are a bit higher than the previous couple of days,
ranging from 15-25%.

Environmental conditions heading into Monday will become more
favorable for more widespread storm activity to materialize with the
latest NBM showing widespread PoPs on the order of 50-70% across
much south-central AZ and southeast AZ. The subtropical high will
remain positioned near the Four Corners Region, resulting in better
moisture advection as PWATs exceed 1.5" along with low-level mixing
ratios exceeding 11 g/kg, providing higher instability and weaker
convective inhibition. In addition, guidance is indicating an
increase in upper-level divergence as a weak easterly wave moves
into northwestern Chihuahua in northern Mexico, which will likely
aid in higher thunderstorm coverage and sustenance. Storms are
likely to develop across the higher terrain areas of eastern AZ as
well as across southeast AZ, with activity moving westward with
strong outflow/multiple collisions resulting in additional storm
development across the lower deserts. Strong downburst wind gusts,
locally heavy rainfall, as well as areas of blowing dust in the
typical dust prone areas will all be likely.

Afternoon high temperatures today will still approach the 110 degree
mark across the majority of the lower desert communities, with areas
of Major HeatRisk. Thus, an Extreme Heat Warning remains in
effect through this evening. Heading into Monday, due to heights
aloft further lowering, afternoon highs will be 2-3 degrees
cooler, which will be enough for HeatRisk levels to drop into the
moderate category and thus ending the extreme heat episode.

&&

.LONG TERM /Tuesday through Saturday/...
Conditions will remain favorable through the middle of the week
for additional monsoonal activity. Depending on how active Monday
turns out, Tuesday could actually be more of a down day given a
worked over atmosphere and thus even though there is still
potential for storm activity, especially across the higher terrain
areas, NBM PoPs for Tuesday are lower, mostly ranging between
30-50%. Another more active period appears to be in the cards for
late Wednesday into the first half of Thursday. The flow by
Wednesday is forecast to shift out of the south as the subtropical
high shifts into Texas and a upper-level low moves off the coast
of California. This southerly flow is likely to bring additional
moisture northward from Mexico, with projected PWATs increasing to
1.7-2.0" and low-level mixing ratios increasing to 12-13 g/kg. In
addition, there will likely more favorable upper-level forcing as
both the GFS and ECMWF do indicate an upper-level wave moving
into the region from Mexico, which will likely enhance the
convective activity with flash flooding becoming more of a threat
given the deeper moisture profiles that will be in place. The
latest NBM PoPs for late Wednesday through the first part of
Thursday currently range between 50-60% across much of south-
central and southeast AZ.

Heading towards the end of the week and next weekend, the guidance
is in good agreement in showing the subtropical high shifting
towards the Gulf Coast Region while the aforementioned upper-
level low remains situated off the west coast. This pattern
configuration will cause the flow to shift more out of the
southwest, bringing in drier air as PWATs drop under 1.2-1.3". As
a result, an overall downtrend in storm activity is likely.

With the lowering heights aloft and as well as an increase in
convective activity and cloud cover, temperatures throughout the
upcoming work week are expected to gradually cool with afternoon
highs expected to fall to near seasonal levels by Tuesday and
potentially a few degrees below normal by the latter half of the
week. Temperatures do eventually trend slightly back up again by
next weekend, but to near seasonal levels with no extreme heat in
sight.

&&

.AVIATION...Updated at 1801Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
The main weather concern will be strong outflow winds, blowing
dust, and VCTS/TS at the terminals. There is good confidence that
one or multiple outflow boundaries will move through the terminals
this evening, with wind gusts up to 20-30 kts anticipated and
around 50% chance for peak gusts greater than 30 kts. The outflow
winds will be capable of bringing a wall of dust through the
metro. There will also be slight chances (20%) for VCTS/TS. Timing
of activity tonight is favored between 02-06Z, although since
confidence remains low for TS possibilities a PROB30 remains in
the latest TAF package. Cloud bases during thunderstorm activity
are only expected to be as low at 10Kft, otherwise FEW-SCT high
clouds will persist through the period.

Before this evening, winds should generally be light (AOB 10 kts),
with KPHX and KIWA remaining westerly and KDVT and KSDL remaining
VRB. Confidence in wind direction is then very low due to the
potential outflows moving through this evening, however, southerly
directions look preferred, with a tendency towards southeast late
evening into the overnight hours.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation weather concerns are expected through the next
24 hours under periods of FEW-SCT mid to high cloud decks and
otherwise mostly clear skies. At KIPL, winds will primarily stay
southeasterly. At KBLH, winds will generally fluctuate between SE
and SSW. Overall, wind speeds should generally remain AOB 12 kts.
A distant thunderstorm outflow reaching KBLH this evening cannot
be ruled out, which would result in an abrupt wind shift and
potentially some VIS restrictions due to lofted/blowing dust.

&&

.FIRE WEATHER...
Hot temperatures with afternoon highs around 110 degrees can be
expected across the lower deserts today, before gradual cooling
to more seasonal levels takes place during the upcoming week.
Elevated moisture levels with maintain afternoon MinRHs
throughout the upcoming week above 20% along with good to
excellent overnight recoveries. Shower and thunderstorm activity
will become more widespread through the first half of the week.
The chances of wetting rainfall will also increase significantly
with the increasing convective coverage. Outside of gusty and
erratic winds due to thunderstorms, winds will follow the familiar
diurnal trends, with typical afternoon upslope breeziness around
20 mph.

&&

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

CA...Extreme Heat Warning until 8 PM PDT this evening for CAZ560>570.

&&

$$

SHORT TERM...Lojero
LONG TERM...Lojero
AVIATION...Benedict/Ryan
FIRE WEATHER...Lojero