Mount Signal, California Weather Forecast Discussion

207
FXUS65 KPSR 052104
AFDPSR
Area Forecast Discussion
National Weather Service Phoenix AZ
204 PM MST Sun Oct 5 2025
.KEY MESSAGES...
- A gradual warming trend will begin today, with afternoon lower
  desert high temperatures returning to the middle 90s midweek
  and upper 90s to 100 degrees late week.
- Increasing rain chances late week into next weekend with a non-
  zero chance for impactful flooding rainfall possible, but
  forecast confidence remains low at this time.
&&
.SHORT TERM /TODAY THROUGH TUESDAY/...
The entire state of AZ and southeast CA is cloud-free this
afternoon with dry west-southwest flow around the base of a long-
wave trough across the western CONUS. The dry conditions and clear
skies resulted in a chilly start to the day for most of the
region, with lower desert lows mostly in the upper 50s to middle
60s. The Flagstaff area started out near to below freezing. High
temperatures this afternoon will be a few degrees warmer than
yesterday, with lower deserts topping out in the upper 80s to
around 90 degrees.
The dry conditions will continue through early this week, with
persistent southwest flow. Temperatures however, will start to
warm up as the long-wave trough weakens a bit and 500mb heights
slowly rise. A few degrees of warming is expected each day, with
latest NBM forecast showing high temperatures at to slightly above
daily averages by Tuesday, with mid-90s for the lower deserts.
Morning lows will slowly warm too, but will remain seasonably cool
through Tuesday with a lot of upper 50s and 60s.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Forecast uncertainty rises considerably during the latter half
of the week with guidance still showing at least some minimal
potential for heavy rainfall and impactful weather by next
weekend. Starting Wednesday, guidance is in very good agreement
showing decent mid-level moisture advecting into the area from the
east, eventually spreading through most of Arizona by Thursday.
This first batch of moisture is not likely to amount to a whole
lot as we are likely to still be under overall subsident flow
aloft and moisture in the low levels should remain fairly limited.
We should see increased clouds Wednesday into Thursday, but rain
chances are likely to be mostly limited to the Arizona high
terrain with PoPs still at most in a 10-20% range. Temperatures
during this time will also continue to warm up as the subtropical
ridge is likely to strengthen and nudge farther to the west into
our region. NBM forecast highs show readings across the lower
deserts in the mid 90s across southeast California to the upper
90s to 100 degrees across south-central Arizona.
Also occurring during the middle of the week, TC Priscilla is
forecast to continue to slowly track to the northwest staying to
the south and west of southern Baja. The latest NHC track has
Priscilla staying well west of Baja later this week with models
showing uncertainty with its track during its eventual
dissipation stage (likely on Thursday and Friday). The most likely
scenario has Priscilla staying west of Baja as it eventually
dissipates later this week, but we are still expected to see at
least some additional moisture advection into our region. This
moisture should eventually come into play as ensembles show a
deep Pacific low setting up off the Pacific Northwest at the same
time.
Model uncertainty is still too high to really have a good idea
on what will happen later this week into next weekend, but one
ingredient (moisture) is nearly certain to be in place. At some
point, the Pacific trough and an associated upper level jet is
likely to place our region within a fairly favorable area for
forcing for rainfall. How far south the trough and jet tracks is
still uncertain and it is definitely possible it will stay too far
to the north to really give our region much in the way of rain
chances. However, a stronger and more southerly track to the
trough may provide portions of our region with chances for heavier
precipitation by next weekend. NBM PoPs have come up slightly
(15-30%) from later Thursday through next weekend, and favor a
progression from southeast CA and northwest AZ initially late
Thursday into Friday to more central portions of AZ next weekend.
It may take several more days to have a good idea on how this
weather event will unfold.
&&
.AVIATION...Updated at 1730Z.
South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation weather concerns under clear skies are expected
through the forecast period. Winds will continue to exhibit the
typical diurnal tendencies with speeds remaining aob 7 kts at all
terminals. Periods of calm and vrb winds can also be expected
before the onset of diurnal wind shifts.
Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation weather concerns under clear skies are expected at the
SE California terminals throughout the TAF period. Winds at KIPL
will become SE this afternoon and shift back around to the W this
evening. Winds at KBLH will remain N-NE through this afternoon and
become more light and vrb after sunset.
&&
.FIRE WEATHER...
Dry conditions with no chances for rain are expected through the
first half of the week. Temperatures will gradually warm during
the period reaching above normal by Tuesday. Expect light winds
through at least Tuesday, generally following diurnal patterns.
Daily MinRHs of 10-20% will continue through Wednesday, with
overnight recoveries of 30-50%. There should be increasing
chances for wetting rainfall by the end of the week, however,
better chances exist for next weekend and forecast confidence
remains low. However, there is at least high confidence that there
will be an increase in moisture by the end of next week pushing
minRHs into the 20-30% range with overnight recoveries of 45-65%.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
SHORT TERM...Benedict
LONG TERM...Kuhlman/Benedict
AVIATION...Salerno
FIRE WEATHER...Benedict/Kuhlman

NWS PSR Office Area Forecast Discussion