085
FXUS65 KPSR 190521
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1021 PM MST Fri Sep 18 2026

.UPDATE...06Z Aviation Discussion.

&&

.KEY MESSAGES...

- Dry and tranquil weather conditions with near zero rain chances
  can be expected through this weekend.

- Near to slightly above normal temperatures will persist through
  the next several days.

- A low pressure system and moisture return early next week will
  bring a return of rain chances to at least the high terrain of
  northern and eastern Arizona.

&&

.SHORT TERM /TODAY THROUGH SUNDAY/...
Latest water vapor satellite imagery depicts an upper-level low
traversing the northern Great Basin, with southwest flow along the
southern periphery injecting a much drier air mass into the region.
Latest SPC mesoanalysis shows precipitable water values noticeably
lower compared to the last 24-48 hours with values ranging between
0.8-1.1" across south-central AZ to between 0.5-0.8" across the
western deserts, with even lower values expected heading into this
weekend. Even though much drier air has been advected aloft, surface
moisture remains abundant with dewpoints in the mid to upper 60s
still hanging on across the lower deserts of south-central AZ.
However, this drier air aloft is expected to eventually scour out
the surface moisture as dewpoints are projected to drop into the 50s
and even into 40s across some areas by this evening with
dewpoints mostly in the 30s and 40s heading into the weekend.
Therefore, given the abundance of dry air, generally clear skies
with zero rain/storm chances are expected throughout the weekend.
Temperatures will remain near steady state through the weekend
with afternoon highs generally in the upper 90s to low 100s and
early morning lows generally in the 70s across much of the lower
deserts along with Minor HeatRisk.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Heading into early next week, there is good confidence that a
Pacific low will move to the central/southern coast of California
by the end of the day Monday. Exactly how this low evolves once
reaching the coast is still a little uncertain, but latest model
consensus suggests the low will track ENE inland staying mostly
north of the local area and driving a chance for showers and storms
across northern AZ. Conceptually this is not a bad setup for a
transitional severe weather event with potential frontogenetical
forcing and a moderately strong upper level jet with higher shear,
but rebounding quickly from the very dry air this weekend and
getting sufficient moisture in here to support any lower desert rain
chance will be tough. Model guidance does at least support a slow
return of moisture Monday through next week, more so coming from the
southeast like typical early stages of the monsoon.

Model guidance is also pointing toward a strong ridge developing
through the middle of the U.S. with the subtropical high
restrengthening near/over Texas by mid to late week. This would keep
the Desert Southwest under predominant southwest flow which is not
the most ideal setup for lower desert storm chances, especially not
for southeast CA and southwest AZ. Latest NBM forecast has PoPs
focused primarily across northern and eastern AZ each day next week
with only minor (10-20%) PoPs for south-central AZ lower deserts in
the evenings. The one thing this pattern does open the door for, the
longer it persists, is potential Eastern Pacific tropical moisture
advecting north.

Temperatures through next week will mostly stay the same day-to-day,
with highs in the upper 90s to lower 100s, which will be around 2-5
degrees above normal, and lows remaining mostly in the 70s. The
temperatures will lead to widespread Minor HeatRisk through at least
the first half of the week with a trend toward areas of Moderate
HeatRisk by the second half of the week as morning low temperatures
creep back up.

&&

.AVIATION...Updated at 0520Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation weather concerns with mostly clear skies are
anticipated through the forecast period. Winds will continue to
follow typical diurnal tendencies with speeds around 8 kts or
less. Extended periods of calm and vrb conditions can also be
anticipated, especially prior to the onset of wind shifts.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation weather concerns will exist at the SE California
terminals under clear skies. Winds will follow diurnal patterns at
both terminals with mainly a W component at KIPL and S-SW at KBLH.
Speeds should remain around 10 kts or less with limited gusts, and
extended periods nearly calm conditions.

&&

.FIRE WEATHER...
Overall there are no fire weather concerns through the next week. A
drying trend will continue today through this weekend with no
rain expected through at least the start of next week. Minimum RH
values this afternoon will be around 20-35% across south-central
AZ to 10- 20% across southeast CA and southwest AZ. The minimum
RHs will then dip to 10-20% for nearly all areas this weekend.
Overnight recoveries across south-central AZ will still be good
tonight at 45- 75%, but then falls lower this weekend. There will
be a gradual return of moisture next week, best across eastern AZ
and there will be an increase in rain chances again, but as of now
rain chances look to primarily favor northern and eastern AZ high
terrain. Besides a potential increase in breeziness early next
week with a weather system, 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...Lojero
LONG TERM...Benedict
AVIATION...Salerno
FIRE WEATHER...Benedict

NWS Phoenix (PSR) Office