140
FXUS65 KPSR 162351
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
451 PM MST Thu Jul 16 2026

.UPDATE...Updated 00z Aviation Discussion...

&&

.KEY MESSAGES...

- Temperatures will cool across much of Arizona dropping to below
normal levels while southeast California maintains near normal
readings.

- Showers and thunderstorms will become more widespread across
eastern and central Arizona through Friday with the potential for
heavy rainfall and localized flash flooding.

- A decrease in thunderstorm coverage across lower elevations will
arrive this weekend with the better chances favoring Arizona high
terrain locations.

&&

.SHORT TERM /Today through Friday/...
Early afternoon satellite imagery depicts several small MCVs
traversing the region adding ascent to an already favorable
underlying synoptic pattern of strong divergence aloft atop
deepening moisture profiles. In fact, 12-15 g/kg low level mixing
ratios have spread across much of the CWA supporting scattered
showers ahead of many of these vorticity features. On the other
hand, this thicker moisture has negatively affected insolation over
much of the region yielding limited instability with notable
inhibition still present. This evolution has added complexity and
greater uncertainty to the forecast over the next 36-48 hours as
most modeling systems have not fully captured the extent of cloud
cover and ongoing showers. One consequence of this allows for the
cancellation of the Extreme Heat warning over the western CWA as
clouds and rain have negated intense heating and associated heat
impacts.

Despite all the convectively detrimental features across the local
forecast area, there are a few regional features which could
eventually encourage storms over south-central Arizona tonight into
Friday morning. Intense ascent between 2 well defined easterly waves
(one over central Baja and the other over west Texas) feeding on
1500+ J/kg MLCape across northeast Sonora has fostered explosive
convective development with evidence of a congealing MCS already
this afternoon. High resolution modeling capturing this complex
suggests outflow and vorticity advection forcing new development
over southern Arizona by early evening. While outflow will not be as
strong as previous days, the combined effect with synoptic energy
importation may bring activity towards the Phoenix metro late
evening. Concurrently, a shortwave near the four corners captured in
NE flow was tapping an unstable airmass over northern Arizona, and
also heading towards south-central Arizona tonight.

As a result, there is growing evidence that multiple MCVs and plume
of higher theta-e congeal somewhere around Pinal/eastern Maricopa
counties overnight as discussed in an alternative forecast outcome
yesterday. While MLCape/DCape will be substantially lower during the
overnight, MUCape around 500-750 J/kg will still be present albeit
with deteriorating midlevel lapse rates. Nevertheless, as mixing
ratios reach 15 g/kg and total column PWATs exceed 2.00", any amount
of focused ascent should sufficient for scattered showers and
thunderstorms. Very efficient rainfall rates with the potential for
warm rain processes could yield at least 2-3"/hr given the moisture
profiles, and this scenario matches many historical late night/early
morning events that have produced significant flooding around the
Phoenix metro. The current Flood Watch may need local extensions
through Friday morning once area of storms become established
overnight. Otherwise, deep convection should eventually exhaust
elevated instability by Friday afternoon as atmospheric profiles
become moist adiabatic. While a few lingering showers may persist
through the afternoon, there is very little evidence of renewed
convection during the afternoon/evening given the expected expansive
thick cloud cover left over from the morning activity.

&&

.LONG TERM /Saturday through Wednesday/...
Although some uncertainty remains, guidance continues to trend drier
for this weekend, particularly the GEFS. This drier air is expected
to advect in from the south southwest starting Friday morning and
continue through most of Saturday, lowering PWATs to as low as 1.4-
1.5", but the Euro maintains a more optimistic 1.7-1.9". The
easterly wave is also forecast to weaken while it briefly shifts
back toward central Texas. The combination of the expected drying,
very little instability, and weaker upper level support is likely to
limit shower and thunderstorm potential on Saturday. As of now, much
of the lower deserts should stay quiet on Saturday, while scattered
showers and storms are much more likely over the Arizona high
terrain. Temperatures will begin to recover starting Saturday, but
daytime highs are still likely to fall short of 100 degrees in the
Phoenix area.

Starting Sunday into early next week, the subtropical ridge is
likely to become more elongated from the Great Basin to the Lower MS
River Valley. The remnants of the easterly wave or even a newly
developed disturbance may also become more of a player for monsoon
activity by around Monday or Tuesday as moisture remains plenty
adequate for convection. An increase in easterly upper level winds
across Texas may eventually stretch into the Desert Southwest by
late Monday into Tuesday which could help drive monsoon activity
throughout portions of the lower deserts again. NBM PoPs still favor
the Arizona high terrain through the period, but it seems likely the
lower deserts will see another day or two of active weather.

Forecast temperatures for next week show a gradual upward trend,
despite fairly high model spread. Lower desert daytime highs may
again reach 100 degrees in the Phoenix area by Monday and eventually
back to near normal during the latter half of next week. Locations
across southeast California and southwest Arizona are likely to
maintain near normal temperatures throughout next week.

&&

.AVIATION...Updated at 2345Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Heavy rainfall and thunderstorm impacts along with some gusty
winds will be the main aviation weather issues through early
Friday. In the meantime, through at least 03-04z, mostly tranquil
weather will prevail with westerly winds aob 10 kts. Thereafter, a
complex of thunderstorms over southeast AZ will gradually shift
northwestward with a gusty southeasterly outflow moving in after
04z with additional shower and thunderstorm activity likely to
erupt along and behind the outflow. Main uncertainty in the
forecast lies in the general location of the heaviest activity as
it could be east of the terminals or directly over the terminals.
PROB30 group for thunderstorms and thus MVFR visibilities remain
in effect given the uncertainty in the general location of the
heaviest activity with several amendments to the TAFs likely
through the evening and overnight as confidence grows. VCSH will
likely continue through at least Friday morning with easterly
winds persisting potentially all day Friday with no westerly
shift. SCT-BKN cloud bases aoa 10 kft will be common throughout
the period with the potential for bases to lower as low as 6-7 kft
in shower and thunderstorm activity, especially during the
overnight period.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation concerns are expected during the next 24 hours
under passing mid to high cloud decks. Winds will generally remain
out of the southeast at KIPL and out of the south at KBLH with
overall speeds between 8-15 kts.

&&

.FIRE WEATHER...
Active monsoon weather with elevated moisture levels will continue
through the rest of the week. Shower and thunderstorm chances will
increase over the eastern districts today with only isolated chances
over the western districts. Localized heavy rainfall is expected
today into early Friday across the eastern districts with some
potential for gusty outflow winds late this afternoon and early
evening. MinRHs will be 35-55% for the eastern districts through
Saturday to 20-35% across the western districts. Outside of
potential thunderstorm outflows, winds for the eastern districts
will tend to be light and somewhat favor diurnal trends. Winds will
predominately favor the south and be breezy at times across the
western districts.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Flood Watch through late tonight for AZZ534-537>563.

CA...None.
&&

$$

SHORT TERM...18
LONG TERM...Kuhlman
AVIATION...Lojero
FIRE WEATHER...Kuhlman

NWS Phoenix (PSR) Office