126
FXUS65 KPSR 191018
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
318 AM MST Wed Aug 19 2026

.KEY MESSAGES...

- Scattered thunderstorms are expected this afternoon and evening
  across eastern and south-central Arizona. Strong gusty winds,
  blowing dust and locally heavy rainfall will be possible.

- Temperatures are forecast to remain several degrees above daily
  normals through the rest of the week with lower desert highs
  ranging between 107-113 degrees and overnight lows generally in
  the mid 80s to low 90s.

- Extreme Heat Warnings are in effect through Friday evening due
  to continued areas of major HeatRisk.

- Thunderstorm chances will continue through Thursday before
  decreasing in coverage by Friday or Saturday.

&&

.SHORT TERM /TODAY THROUGH THURSDAY/...
Today is potentially shaping up to be a big weather day with
guidance finally coming together to suggest scattered
thunderstorms (some strong to severe) affecting portions of
southern and central Arizona. A strong Gulf moisture surge is
currently underway with 70-75 degree surface dew points in the
Yuma area to the mid to upper 60s now as far north as Phoenix.
Even though this is shallow, it should greatly improve upon last
evening 8-9 g/kg mixing ratios, with guidance indicating 10-12
g/kg across the area by late afternoon.

As stated yesterday, the subtropical high is reforming across
northern Arizona allowing for easterly mid-level flow across
southern Arizona while allowing for Gulf moisture surges to
recommence. The overall lack of convection yesterday has allowed
for the atmosphere to heat up with MUCAPEs improving to around 500
J/kg. The added moisture from the ongoing Gulf surge is forecast
to improve MUCAPEs to at least 1000 J/kg across all of southern
and most of central Arizona to as high as 2000 J/kg across
southeast Arizona by early afternoon. The strong instability will
also coincide with some upper level forcing as southeast and
south-central Arizona is forecast to fall within the right
entrance region of a weak upper level jet max associated with the
weak disturbance over northwest Mexico.

Forecast soundings also show high DCAPEs of 1400-1800 J/kg over
the lower deserts this afternoon/early evening. The high
instability and weakening CIN this afternoon are expected to
allow for scattered thunderstorms to develop along the Mogollon
Rim into the White Mtns and over portions of southeast Arizona. A
modest 5-10 kt east northeasterly steering flow this afternoon
should allow for storms and storm outflows to track to the west
southwest toward the south-central Arizona lower deserts by 5-6
PM. A second stronger cluster of storms is likely to form across
Pima County with indications of a north northwestward outflow
propagating into Pinal and Maricopa Counties. It is very plausible
we will have colliding outflows somewhere over the Phoenix metro
early this evening giving rise to additional storm development.
Modest 0-6km shear of 20-25kts should help to maintain some of
these storms with a few becoming strong to severe. The biggest
threat with any strong to severe storms will be damaging winds due
to a high DCAPE environment which should also result in localized
dense blowing dust. SPC has included a Marginal Risk for severe
storms across Gila, Pinal, and much of Maricopa County for today.
We also can`t rule out the threat for localized heavy rainfall
today, but storm movement should be enough to keep most storms
from producing more than an inch or so over any particular
location. The latest HRRR suggests storms will make their way to
near the Maricopa/Yuma-La Paz border late this evening while also
weakening as they encounter an increasingly capped environment.

Thursday may bring another fairly active weather day as moisture
will remain plentiful across the area and the subtropical high
center moves to over the Four Corners area. However, it seems
fairly likely the storm coverage this evening will be widespread
enough to at least somewhat overturn the atmosphere. Lingering
clouds well into Thursday morning may also inhibit heating a bit
on Thursday, keeping instability lower than today. That being
said, if today is not as active as anticipated, Thursday is likely
to be the biggest storm coverage day. As of right now, PoPs today
are higher than Thursday.

Hot and humid conditions are expected today with lower desert
afternoon highs between 108-112 degrees, but much higher heat
indices are forecast for locations across southeast California
through the Lower CO River Valley. Expect late afternoon heat
indices of 113-120 degrees in the aforementioned areas.
Temperatures are more uncertain for Thursday due to potential
impacts from storms this evening and lingering clouds, but NBM
guidance indicates very similar highs and heat indices again
breaching 110 degrees over the majority of the lower deserts.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Hot and somewhat humid conditions are expected to prevail through
the upcoming weekend with a high probability of the Extreme Heat
Warnings being extended soon. Forecast uncertainty has been an
issue for late this week into the weekend as storm chances were
higher with model runs earlier this week. However, it now seems
more likely than not drier air will move into the area beginning
Friday leading to much more limited shower and storm chances
through the upcoming weekend. The lower storm coverage and fairly
consistent upper level heights should keep daily highs right
around 110 degrees or even a couple degrees above through the
weekend. Guidance does hint at some better moisture advecting into
the area early next week, but the latest trends show the ridge
center drifting back toward our region. If that holds true, our
convective potential should remain on the lower side with little
to no relief from the hot temperatures.

&&

.AVIATION...Updated at 0915Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: The main
aviation concerns this TAF package will be the potential for strong
gusty winds, blowing dust with reduced visibility, and thunderstorm
activity this evening. Winds at KSDL, KDVT, and KIWA will follow
their typical patterns this morning with light and variable at KSDL
and KDVT and SE`rly at KIWA prior to the development of westerly
winds this afternoon. At KPHX, westerly winds are expected to go
light and variable during the mid morning hours prior to
redeveloping westerly winds this afternoon. Occasional gusts in the
upper teens to around 20 kt is possible this afternoon.

By Wednesday evening, conditions will be more favorable for strong,
gusty outflows to survive into the lower deserts. Multiple outflows
are possible, but confidence is highest in an outflow from the
south/southeast. But an outflow from the northeast could move in an
hour or two prior to the south/southeast outflow. These outflows
could spark additional SHRA/TSRA in the Phoenix Airspace. Chances
for SHRA/TSRA remain around 20%. Additionally, the strong gusty
outflow winds from the south or southeast could bring blowing/lofted
dust and result in temporary surface VIS or slantwise VIS
restrictions.

Southeast California/Southwest Arizona including KIPL and KBLH:
No weather concerns will exist through the next 24 hours under
FEW-SCT high cloud decks. Winds at KIPL will favor southeasterly
with speeds AOB 10 kts sustained. Winds at KBLH will be southerly
with occasional gusts to around 20 kts, mainly this morning and
afternoon.

&&

.FIRE WEATHER...
For today, expect above normal temperatures with increasing
moisture and rain chances. Scattered thunderstorms producing
gusty winds are likely to impact the eastern districts from late
afternoon through this evening. Elevated moisture levels will
persist through Thursday with additional chances for scattered
showers and storms before some slight drying and lower rain
chances occurs Friday into the weekend. MinRHs of 20-30% are
anticipated through Thursday before lowering to 15-25% beginning
Friday. Outside of gusty and erratic winds near any thunderstorm,
overall winds will follow the typical diurnal tendencies with some
modest afternoon upslope gustiness.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning until 8 PM MST Friday for AZZ530>544-546-
     548>551-553>555-559-560.

     Blowing Dust Advisory from 5 PM this afternoon to 10 PM MST this
     evening for AZZ538>540-550-551-553-554-559.

CA...Extreme Heat Warning until 8 PM PDT Friday for CAZ562-565>567-
     569-570.

&&

$$

SHORT TERM...Kuhlman
LONG TERM...Kuhlman
AVIATION...Whittock/Berislavich
FIRE WEATHER...Kuhlman