903
FXUS65 KPSR 151727
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1027 AM MST Wed Oct 15 2025

.UPDATE...Updated Aviation Discussion.

&&

.KEY MESSAGES...

- Dry and tranquil weather conditions will prevail through the
weekend with temperatures remaining below normal.

&&

.SHORT TERM /Today through Thursday/...
Deep troughing was pivoting inland over the western Conus early this
morning as the primary negative PV anomaly responds to seasonally
strong jet energy shifting east into the Rockies. This increasingly
deep SW flow has continues to erode moisture profiles across Arizona
with objective analysis suggesting low level mixing ratios falling
near 7 g/kg and total column PWATS under 0.75". An ill-defined cold
front crossing the California coastal range will continue its
eastward progression into central Arizona today in association with
the trough axis shifting well inland. This evolution will ensure an
additional influence of downsloping dry air further eliminating
moisture content such that even cloud formation will be hampered by
Thursday. Otherwise, the southern extent of the troughing will keep
H5 heights trapped in a 572-576dm range; and forecast confidence is
excellent that temperatures will hover a solid 8F-12F below the
daily normals. This will likely include the first seasonal taste of
overnight lows in the 40s for the more sheltered, rural valley
locations.

&&

.LONG TERM /Friday through Tuesday/...
Lingering positively tilted troughing associated with the exiting
system will continue to affect the forecast area late in the week
with a reinforcing shot of lower midlevel heights and dry NW flow
tempering any warming trend. However, all modeling suites are in
good agreement that shortwave ridging and H5 heights in excess of
588dm will temporarily build into the SW Conus over the weekend
allowing temperatures to finally rebound closer to the seasonal
normal. Early next week, ensemble membership continues to display
uncertainty regarding renewed Pacific troughing entering the
western Conus. One subset of models (including many GEFS members)
phase northern stream energy with lingering weaknesses in the height
field off the California coast into deepening progressive downstream
flow (a very La Nina-like pattern). However, another subset of
models (now flip-flopping from the operational GFS to ECMWF and many
CMC members) disconnect these features without any phasing resulting
in lower heights, cooler temperatures, and potentially some low
impact unsettled weather over the SW Conus. Recent NBM output seems
to favor the former solution reverting a cooling trend into a near
persistence forecast while advertising light winds and very low
POPs. Given the wide range among ensemble members, forecast
confidence during this time frame is somewhat lower than usual,
albeit with limited impacts regardless of the outcome.

&&

.AVIATION...Updated at 1730Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No major weather issues should exist through Thursday afternoon. A
FEW-SCT deck of clouds with bases around 6-8 kft AGL persists late
this morning, with BKN decks focused to the east of the Phoenix
airspace. Clouds will scatter out through the afternoon with clear
skies returning by sunset. Confidence is good that light and
variable winds become westerly over the next few hours with speeds
mostly under 10 kts. This west component should persist much
longer into the overnight than usual. Confidence is moderate on a
full east shift occurring early Thursday morning at KPHX, but
winds will be very light (AOB 5 kts) across the terminals Thursday
morning regardless of direction.

Southeast California/Southwest Arizona including KIPL and KBLH:
No weather concerns will exist through Thursday morning with
lingering 6-7K ft AGL cloud decks late this morning dissipating
early this afternoon. NW winds will be preferred through the
period with only limited gusts. Periods of nearly calm conditions
will be common later tonight.

&&

.FIRE WEATHER...
Dry, tranquil weather conditions will prevail through early next
week under a steady drying trend. Minimum humidity levels will only
fall into a 25-50% range today, then gradually deteriorate closer to
a 15-30% over the weekend. With the exception of some far western
district locations, overnight recovery will largely be good to
excellent above 50%. Winds will be far weaker the remainder of the
week with limited gustiness. Winds should be rather weak with
limited gustiness through early next week under a typical diurnal
upslope/nocturnal drainage pattern.

&&

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

$$

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