520
FXUS65 KPSR 202010
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
110 PM MST Sun Sep 20 2026

.KEY MESSAGES...

- Dry, tranquil weather conditions with near to slightly above
normal temperatures will continue through the first half of next
week.

- A low pressure system with returning moisture will yield renewed
rainfall chances to at least the high terrain of northern and
eastern Arizona during the latter half of next week.

&&

.SHORT TERM /Today through Tuesday/...
Regional objective analysis shows a shortwave weakening and lifting
into the northern plains while another, deeper negative height
anomaly slowly advances towards the southern California coast. In
between, shortwave ridging has temporarily become established over
the SW Conus with widespread subsidence and H5 heights settled near
588dm. Although very modest height falls will enter the region
Monday as the aforementioned coastal California wave moves inland,
confidence is very good that temperatures will hover very close to
the seasonal normals the next few days. Otherwise, prolonged deep
westerly flow has helped scour away moisture with low level mixing
ratios falling under 7 g/kg and the more favorable 10 g/kg pool now
sequestered south of the international border such that only shallow
insolation/terrain based convection will bubble over the region.

As height/pressure falls advance towards the forecast area the next
48 hours, low level southerly return flow will develop allowing a
rebound in moisture, albeit initially somewhat discontinuous through
the atmospheric column. Nevertheless, as early as tomorrow
afternoon, boundary layer mixing ratios may rebound closer to 9 g/kg
while total column PWATS recover from under 0.75" closer to 1.25".
Still residing under anti-cyclonic flow aloft, rain/thunderstorm
prospects will be nearly neglible tomorrow afternoon. However,
chances for deep convection increase Tuesday afternoon across high
terrain locations east of Phoenix as ascent mechanisms approach the
region, including the potential for a notable jet streak streaming
north from Sonora. Thermodynamics across lower elevations will
remain somewhat detrimental towards sustained storms with poor
midlevel lapse rates limiting MLCape and lingering inhibition given
the modest moisture availability.

&&

.LONG TERM /Wednesday through Saturday/...
After a low pressure system advects into the northern Plains by the
middle of the week, weak large scale troughing will remain across
the eastern Pacific/West Coast through the end of the week. By the
end of the week, the high pressure system over TX will try to
retrograde over NM/AZ, but it will be battling the large scale
troughing over the West. Ensembles show PWATs staying around 1.0-
1.3" across southern AZ through the end of the week. As a result,
NBM/WPC PoPs for the end of the week continue to show 30-50% across
the higher terrain of southern Gila County and 10-20% across the
south-central AZ lower deserts.

Temperatures this week will remain largely unchanged, but are
expected to dip a couple degrees midweek as the low pressure system
moves north of our area causing H5 heights to dip to around 582-585
dm. Regardless, afternoon highs will generally be in the upper 90s
to low 100s across the lower deserts, and in the upper 80s to mid
90s across the higher terrain. Morning lows will generally be in the
70s to to low 80s across the lower deserts, and in the 60s across
the higher terrain areas. Morning lows should start to creep up by
the end of the week (more morning lows in the low 80s across the
lower deserts). As a result, widespread minor HeatRisk will continue
through the first half of the week with moderate HeatRisk returning
to the lower deserts for the latter half of the week.

&&

.AVIATION...Updated at 1730Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No major aviation concerns are expected during the TAF period under
increasing mid and high cloud decks. Winds will generally follow
diurnal trends through Monday morning, with speeds AOB 10 kts and
periods of variability likely. By Monday late morning, a more
prolonged period with a southerly cross-runway wind component (for
KPHX, KDVT) is anticipated to develop and may prevent the typical
SW/W switch Monday afternoon. Cloud bases will remain above 8K ft
AGL through the period.


Southeast California/Southwest Arizona including KIPL and KBLH:
The only weather issue during the next 24 hours will be low
confidence on wind directions, especially at KIPL, under BKN high
cloud decks. Winds will generally favor SE/S at both terminals with
speeds below 10 kts, however, directions may veer out of the SW for
a period this evening. Confidence is moderate to good on a period of
VRB winds developing overnight into Monday morning at both
terminals.

&&

.FIRE WEATHER...
Temperatures will remain fairly steady through the upcoming week and
be around 2-5 degrees above normal. Dry conditions with no chances
for showers or storms continue through tomorrow. Daily, low-end,
chances for showers and storms return to the higher terrain areas of
southern Gila County beginning on Tuesday. MinRHs will be around 10-
25% today before increasing to around 15-30% across the central and
western districts and 30-50% across the eastern districts for next
week. Overnight recoveries will range from fair to good across the
central and western districts and good to excellent across the
eastern districts through next week. Besides a slight increase in
breeziness early this upcoming workweek as a weather system moves
through the region, winds will mostly follow typical diurnal
patterns with modest afternoon upslope/upvalley gustiness (15-25
mph).

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.

&&

$$

SHORT TERM...18
LONG TERM...Berislavich
AVIATION...Whittock
FIRE WEATHER...Berislavich

NWS Phoenix (PSR) Office