663
FXUS65 KPSR 041004
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
304 AM MST Tue Aug 4 2026

.KEY MESSAGES...

- Extreme heat will persist through at least the end of the
  workweek with increasing moisture pushing heat indices to around
  110 to 115 degrees for the latter half of the week.

- Shower and thunderstorm chances will favor eastern and
  southeastern Arizona through the rest of the week with gusty
  outflow winds and blowing dust a possibility each day into the
  south-central Arizona lower deserts.

&&

.SHORT TERM /TODAY THROUGH WEDNESDAY/...
An elongated high pressure ridge with H5 heights just shy of the
90th percentile of climatology currently stretches from off the
coast of California through the Desert Southwest into Oklahoma.
There is no well defined high center at the moment, but it is
loosely found over central Arizona. The extreme heat remains the
main forecast concern for at least the next few days as even
though temperatures will dip some, the increased low level
moisture will make it feel just as hot.

The ridge went through a weakening stage Sunday and Monday, but
now has stabilized. Despite the weakening, high temperatures
yesterday barely budged with 112-116 degree readings across the
lower deserts. Thanks to the widespread convection that impacted
southeast Arizona last evening, temperatures across south-central
Arizona are running at least 10 degrees cooler than this time last
night. The cooler start to the day today will help to bring
daytime highs down today with highs of 107-110 degrees in the
Phoenix area to 108-112 degrees across the western lower deserts.
Unfortunately, the increased low level moisture has allowed for
surface dew points to climb into the 60s areawide and we
anticipate this moisture to persist through midweek. As a result,
forecast afternoon heat indices will stay above 110 degrees
across the lower deserts to as high as 118 degrees across
southeast California. Even though the HeatRisk, which doesn`t
factor in humidity, drops to Moderate in many locations today and
Wednesday, the combination of temperatures and humidity will
still be enough to bring extreme heat conditions. The increased
humidity will also help to keep overnight lows very warm with some
locations staying above 90 degrees. However, just like late last
evening, daily chances for storm outflows may end up bringing some
minor relief from the worst of the heat across south-central
Arizona.

Shower and thunderstorm chances today and likely through the rest
of the week are expected to mainly be confined to the eastern
Arizona high terrain. Moisture has improved to a degree, but not
enough across the lower deserts to expect to overcome the
subsidence inversion created by the heat dome in place. CAMs
continue to point toward afternoon storms firing from the White
Mtns through southeast Arizona, but due to a northeasterly
steering flow the bulk of the convection is expected to track
outside of or along the outer edges of our CWA over the next few
days. However, the environment remains well suited for storm
outflows to form with the convection which will have a decent
chance of progressing into Pinal and Maricopa Counties each
evening. The latest HRRR for this evening basically mirrors what
occurred on Monday with gusty south southeasterly outflow winds
and most likely fairly widespread dust eventually reaching the
Phoenix metro late this evening. It would not be impossible for
some showers or even thunderstorms to develop into the lower
deserts today and Wednesday, but due to the strong capping
inversion it would take fairly strong colliding outflows for any
redevelopment to occur over the lower deserts. PoPs for the
Phoenix area are only around 5% today and 10% Wednesday due to the
conditional environment. However, if that 5-10% chance involves a
couple strong storms that manage to go up, that could also create
a cascading scenario where many more pulse type showers and
storms impact the area due to the high amount of available
elevated instability that will be in place.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Little will change with the weather pattern for the rest of this
week and likely well into next week as the high pressure ridge
is expected to remain centered over the Desert Southwest. The
center of the ridge is forecast to somewhat shift farther to the
north by Friday which could help to bring better rain chances, but
guidance shows the ridge also strengthening which will likely
reinforce the subsidence over much of our area. As of now, Thursday
and Friday are expected to follow the same pattern as today and
Wednesday with mostly eastern Arizona high terrain storms and very
conditional 5-15% PoPs into the south-central Arizona lower
deserts. As stated in the short-term discussion, even though it
will be a day-to-day low chance environment for the lower
deserts, it would not be surprising to have a day where the
elevated instability is managed to be tapped into causing some
scattered storms to fire. Hot and humid conditions will continue
to prevail with daytime highs likely nudging upward again late
week as the ridge restrengthens. The Extreme Heat Warning
currently goes through Friday which is very reasonable, but it
will be possible to have a day in there where it fails to reach
criteria over south-central Arizona if convection ends up being
more widespread one evening/overnight.

For the weekend into early next week, ensembles still favor the
ridge basically staying stationary with the center somewhere just
to our north. Some weakening of the ridge is likely to occur by
early next week and depending on how much moisture will be
available we could be looking at a further uptick in monsoon
activity. The GEFS is more optimistic with rain chances by early
next week with activity expanding into central and northern
Arizona, but the EPS holds off until later next week. If
convection does eventually become more widespread and impacts the
lower deserts, temperatures are expected to dip closer to seasonal
normals.

&&

.AVIATION...Updated at 0920Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT;

The main aviation concern during the TAF period will be gusty
outflow winds and reduced VIS due to blowing dust late this evening
into early Wednesday morning. In the meantime, winds are expected to
follow diurnal trends, with and early switch out of the west. Winds
will eventually become breezy during the afternoon hours, with gusts
around 20 kt. Most of the evening will be fairly calm, until an
outflow boundary arrives from the south/southeast sometime between
06-10Z based on current forecast trends. Associated gusts may reach
upwards of 30 kt, and with the orientation of the boundary, another
round of blowing dust is certainly not out of the question. However,
this outflow will be heavily conditional upon how distant convection
over southeast Arizona evolves, so adjustments and amendments should
be expected.

Southeast California/Southwest Arizona including KIPL and KBLH: :

Breezy conditions, mainly at KBLH, will be the main aviation concern
during the TAF period. There, winds will favor a S`rly direction
through the forecast, with gusts during the afternoon around 20-25
kt. Another around of gusts is expected to develop late in the
period, with readings approaching 25-30 kt. Winds at KIPL will be
much weaker, generally ranging 7-15 kt out of the SE. FEW to
occasionally SCT high level clouds will be present through the
majority of the forecast window.

&&

.FIRE WEATHER...
Hot temperatures will continue all week with fairly elevated
humidities, but showers and thunderstorms will mostly remain
over far eastern and southeastern Arizona. Gusty outflow winds are
likely to impact the south-central Arizona lower deserts again
late this evening. MinRHs will continue to improve, climbing to
around 25-30% by Wednesday, while overnight recoveries range
between 40-70%. Outside of storm outflows, winds will mostly
follow diurnal patterns, but southwesterly winds will be dominant
much of the time with afternoon gusts of 15-25 mph at times.

&&

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

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

&&

$$

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