929
FXUS65 KPSR 141704
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1004 AM MST Sun Sep 14 2025

.UPDATE...Updated Aviation Discussion

&&

.KEY MESSAGES...

- Near to slightly below-average temperatures today before
  gradually warming through the early part of the work week.

- No showers or storms expected today through the first half of
  the week, with mostly sunny skies and light winds.

- Potential for a widespread rain event late week into next
  weekend with a push of moisture, but there is still a high
  degree of variability with this forecast.

&&

.SHORT TERM /TODAY THROUGH MONDAY/...
The trough that brought us drier conditions and cooler
temperatures, as well as helped spawn a widely seen tornado in
southeast UT yesterday is moving into the Plains today. Another
shortwave trough is seen moving into OR on water vapor satellite
early this morning. There is also a much weaker low circulation
evident due west of the northern Baja Peninsula. This weak low
may actually play a role in our weather for the end of the week,
but for now weak anti-cyclonic flow is now in place over southern
AZ and SoCal with a strengthening high pressure over north-central
MX expected to slowly expand into the Desert Southwest through
Monday.

Mesoanalysis shows much drier conditions are now in place
across all of AZ and SoCal, with most of the region at or below
0.5" PWAT magnitudes. This dry air will keep rain chances at
nearly 0% for the whole region through at least Monday. The drier
low level conditions, plus the clear skies, are helping maximize
radiational cooling and will continue to result in cooler, more
crisp, mornings. Low temperatures across the lower deserts this
morning will once again be in the low to mid 70s in most urban
centers, with several rural and outlying communities dipping into
the 60s. The same can be said for Monday`s forecast lows, but just
a touch warmer (+1-3 degrees). High temperatures today are
forecast to be right near to just below daily averages, with many
lower desert locations once again coming shy of the century mark.
The little bit of warming into Monday will yield highs 2-4 degrees
warmer, with most urban areas expected to reach 100-103 degrees.
Take advantage of the cooler mornings, but still play it safe in
the afternoons. Long exposure to 90+ degree heat in the afternoons
can still have negative health impacts without proper heat safety
actions.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Forecast confidence through the first half of this coming work
week remains high. High pressure will continue to nudge into the
region, leading to a gradual rise in 500mb heights. Global
ensembles have H5 heights peak around 590dam on Tuesday, which is
around 80th percentile of climatology for this time of year. As a
result surface temperatures will climb slightly above normal for
at least Tuesday and Wednesday. Latest NBM forecast has afternoon
highs reaching 101-105 degrees both days. There will be a slow
return of moisture through Wednesday, enough for some clouds to
develop, but likely not enough still for showers or storms in
South-Central AZ to Southeast CA. Latest NBM PoPs are at <5%
Tuesday and <10% Wednesday.

For late-week into next weekend, confidence is slowly increasing
in favor of a - potentially widespread - rainfall event. However,
there still remains a large spread in outcomes across the 3
primary global ensembles and there are some uncertainties in the
synoptic scale forcing. The interquartile ranges for PWAT,
accumulated precip, and temperatures are still quite large with
the most recent 00Z ensemble runs. So it is still too early to put
any stock in forecast rainfall amounts and impacts. The
confidence is increasing though, largely due to the lower quartile
PWAT forecasts and potential for jet streak support. The 10th
percentile PWAT forecast is near to above normal at 1.1-1.2"
across the lower deserts by Friday. Typical PWAT levels this time
of year are around 0.9-1.0". Greatest PWAT anomalies (>150%)
continue to favor western areas, in SoCal and just offshore. These
areas, and along the Colorado River, look like the more favorable
areas for jet support as well. So, these mentioned areas
currently have the higher odds for rainfall and this lines up with
the latest CPC 6-10 outlook`s highlighted areas with the highest
odds of above normal precip.

As for potential rainfall, it is at least worth mentioning there
are several ensemble members with high rainfall amounts. Around
5-10% of the global ensemble members have 1.00-2.00" rainfall
amounts. However, a lot of these extreme members involve a
tropical circulation moving up the Baja. Right now this definitely
seems like quite a stretch given the majority of members will
have high pressure still firmly in place over northwest MX and
turn any tropical circulations more out to sea. On the other end
of the forecast spectrum, there are still around 25% of model
members with 0.05" or less. This far out in the forecast the
extreme rainfall forecasts are driving up the ensemble means and
with time the forecast may trend more toward the lower median
forecasts. Also, don`t be surprised if come late next week the
rainfall forecast has backed off or become more focused to a
particular area and/or most areas receive just cloud-cover. Still
a lot to parse out with this forecast.

&&

.AVIATION...Updated at 1705Z.

South Central Arizona and Southeast CA including KPHX, KIWA,
KSDL, KDVT, KBLH and KIPL:

No aviation concerns are expected through Monday morning under
mostly clear skies. Winds will overall favor diurnal trends, with
extended periods of variability, especially for the western
terminals. Expect a period of southerly winds midday today before
gradually veering toward the W-SW by mid-late afternoon for the
Phoenix terminals. Speeds will remain generally less than 10 kts
through the period.

&&

.FIRE WEATHER...
Near to slightly below average temperatures will be common across
the region today, with a warm-up to slightly above average by
Tuesday - Wednesday. Winds will be light nearly every day,
following typical diurnal tendencies, with occasional afternoon
gusts up to 10-20 mph. Dry conditions will prevail through the
first half this week with no chances for wetting rains. MinRHs
through Wednesday will mostly range from 15-25% (10-15% today)
across all districts with fair overnight recoveries at 30-50%. The
forecast for late in the week and into the weekend is still
highly uncertain. However, a good push of moisture is expected to
move into the region beginning Thursday, which will increase the
RH levels and will increase odds for showers and storms.

&&

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

$$

SHORT TERM...Benedict
LONG TERM...Benedict
AVIATION...RW/Frieders
FIRE WEATHER...Benedict