871
FXUS65 KPSR 180810
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
110 AM MST Sat Jul 18 2026

.KEY MESSAGES...

- Light shower activity will be possible early this morning before
  transitioning to the higher terrain in the early afternoon.
  Typical monsoon shower and thunderstorm chances will then favor
  the Arizona high terrain through this weekend.

- Thunderstorm chances will increase again during the first half
  of next week, expanding into the lower deserts Tuesday and
  Wednesday.

- Below normal temperatures will linger across south-central AZ
  today through early next week while southeast California
  maintains near normal readings.

&&

.SHORT TERM /Today through Sunday/...
Latest IR WV imagery and 500 mb streamline analysis reveals weak
and chaotic mid-lvl flow with several lobes of vorticity meandering
over the Desert Southwest. There is still ample moisture in place
over south-central AZ with PWATs hovering around 2.00" and ML CAPE
values up to 1000 J/kg. Latest high-res guidance indicates widely
scattered shower activity redeveloping over south-central AZ
early this morning. Each model is showing a different degree of
intensity and areal coverage, however some portion of Maricopa
County could see some measurable rainfall around sunrise with
general totals ranging from a few hundredths to a tenth of an
inch. By this afternoon, isolated showers and thunderstorms will
form over the AZ high terrain and should remain largely outside of
the PSR forecast area aside from a few storms potentially
developing over S Gila County. Due to abundant mid to high lvl
cloud cover and ample boundary layer moisture, high temperatures
will again top out well below normal (8-10 degrees) across
southcentral AZ with most locations remaining in the 80s and 90s.
Further west along the Lower Colorado River valley and SE
California, temperatures are expected to reach closer to daily
normals with highs in the 100-107 degree range.

On Sunday, the subtropical ridge will expand and strengthen over
the Southern Rockies with much of the Desert Southwest remaining
on the southern periphery of the high pressure center. An easterly
wave/inverted trough that continues to bring heavy rainfall to
the TX Hill Country will weaken and slowly progress wwd into far
west TX by Sunday afternoon. Subtle shortwaves ahead of this
feature will continue to provide large scale ascent and a focus
for scattered shower and thunderstorm development over the AZ high
terrain Sunday afternoon and evening. Due to the weak overall
steering flow out of the SE (10-15 kts), showers and storms will
likely not make it to the lower deserts on Sunday evening where
rain chances are 15-20% at best. Temperatures on Sunday will again
be below normal across south- central AZ, however slightly warmer
than today due to the subtle increase in hghts aloft and warming
mid-lvl thermal profiles which will bring afternoon highs closer
to 100 degrees in Phoenix. The western deserts will still see
highs reaching near normal.

&&

.LONG TERM /Monday through Friday/...
By early next week, ensemble members and deterministic guidance
suggest the 500 mb ridge axis over the Southern Rockies will
expand ewd into the Southern Plains as the aforementioned easterly
wave is likely to move into southeastern Arizona by Tuesday. This
will foster increasing southeasterly flow and bring additional
moisture into the lower deserts. High terrain storms are more
likely on Monday, with convection expanding in coverage to include
the lower deserts of south- central AZ on Tuesday. NBM PoPs are
on board with this scenario unfolding with chances increasing from
15-30% late Monday to around 30-50% late Tuesday. If Tuesday ends
up being the bigger day, then Wednesday may be a down day
convective wise. This will all depend on the progression of the
mid-lvl easterly wave and convection from the previous day. Model
guidance shows the disturbance eventually moving to our west by
Thursday as the subtropical high is favored to become more
established over New Mexico and West Texas. If the high does
expand wwd and strengthens to around 594-596 dam, we could be in
for a hotter and slightly drier period of weather through the end
of next week.

NBM temperatures are forecast to gradually creep upward by the
latter half of next week, but locations across south-central and
eastern Arizona are expected to remain near normal through at
least Friday. If the ridge does eventually expand further west, we
may eventually have to deal with highs topping 110 degrees again
by next weekend.

&&

.AVIATION...Updated at 0520Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
SHRA activity with some embedded TS around the vicinity Saturday
morning will be the main aviation weather issue throughout the TAF
period. In the meantime, quiet conditions will persist through at
least the first part of the overnight period with winds generally
light and variable to light easterly. After 10z, most of the hi-
res guidance continues to indicate an area of showers with
embedded TS materializing across northern and northeastern
Maricopa county potentially extending into the Phoenix area.
Uncertainty continues with respect to the overall coverage of the
activity as it develops and thus VCSH remains in the latest TAF
package. Regardless of the overall activity, drier conditions will
move in during the afternoon hours. Uncertainty remains of whether
or not the traditional westerly shift occurs Saturday afternoon
with winds potentially remaining light and variable. SCT-BKN
clouds aoa 10 kft will be common throughout much of the period
with the potential for bases to lower to 8 kft Saturday morning in
SHRA activity.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation weather concerns are expected throughout the TAF
period. At KBLH, winds will generally remain out of the south to
southeast with a period of northeasterly winds expected during the
first part of the overnight period as a weak outflow moves through
from the north. At KIPL, winds will generally remain out of the
southeast through Saturday afternoon with a westerly shift during
the evening hours. Overall speeds will remain generally under 12
kts. FEW to SCT clouds aoa 10 kft will be common throughout the
period.

&&

.FIRE WEATHER...
Recent wetting rainfall has resulted in drastic improvements in fuel
moisture across south-central AZ where ERC values have fallen below
the 25th percentile. Additional rounds of beneficial rainfall will
be possible each day through early next week, especially over the
foothills and high terrain of the eastern districts. Winds will
remain light, mostly below 15 mph this weekend and follow typical
diurnal upslope and downvalley patterns. Elevated moisture levels
will keep minimum afternoon humidity above 20% across the western
districts and between 30-40% over the eastern districts.
Overnight recovery will range from fair to good across the western
districts and very good to excellent for the eastern districts.

&&

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

$$

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