097
FXUS65 KPSR 121000
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
300 AM MST Sat Sep 12 2026

.KEY MESSAGES...

- Abundant moisture will remain situated across the eastern half
  of Arizona well into next week providing at least daily chances
  for isolated showers and thunderstorms.

- Shower and thunderstorm chances will be focused more over the
  high terrain of Northern and Eastern Arizona, but chances will
  also extend into the south-central Arizona lower deserts.

- Near to slightly above normal temperatures are expected this
  weekend and likely through all of next week.

&&

.SHORT TERM /TODAY THROUGH SUNDAY/...
Moisture advection yesterday was stronger than predicted and thus
has left the area under PWATs of 1.7-1.8" and low level mixing
ratios of 12-13 g/kg. This higher than anticipated moisture
allowed for greater instability and lower CIN, which in turn
resulted in more widespread storm coverage during the afternoon
and evening hours over the Arizona high terrain. Eventually that
translated into scattered showers and storms developing southward
toward the Phoenix area late in the evening before gradually
winding down over northern and western Phoenix since midnight.

The weather pattern that is shaping up now and likely to last
through much of next week is a bit complicated and could result
in multiple days of fairly active weather. The subtropical ridge
that brought the hot temperatures during the workweek has weakened
and become more stretched out, while a large scale Pacific trough
is taking shape across the Northwestern U.S. As the subtropical
ridge develops a new center over New Mexico today and gradually
drifts into the Southeastern U.S. by Monday, the Pacific trough
will become more predominant over the Western U.S., while keeping
a consistent flow of moisture northward into the eastern half of
Arizona.

Hi-res CAMs yesterday under estimated the storm coverage for last
evening, although it did have the general areas depicted well.
Today and even Sunday will carry additional chances for showers
and storms, but coverage is expected to be much less as there will
not likely be a trigger like the weak shortwave that moved
through last evening. The latest CAM runs show isolated to at
most scattered high terrain showers and storms today and Sunday
with no clear signs of any activity developing over the lower
deserts. Temperatures today will drop off from the 5-7 degree
above normal readings yesterday and settle in right around
seasonal normals through the rest of the weekend.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
The first half of next week will continue to bring rain chances
across the eastern half of Arizona as the Pacific trough lingers
just to our north and northwest and the ridge stays centered over
the Southeastern U.S. This will continue place Arizona in a south
southwesterly flow area providing periods of moisture advection
out of moisture rich northern/western Mexico. The biggest
question that remains is what day or days will represent the best
chances for more than just scattered showers and isolated storms.
Models do agree plentiful moisture will remain over eastern and
central Arizona through at least the middle of next week with
PWATs running 150-180% of normal and low level mixing ratios
anywhere from 11-14 g/kg. However, there are uncertainties with
the amount of instability due to a good deal of forecast cloud
cover and lack of any obvious trigger mechanisms. Last night`s
model runs were more optimistic with upper level support and this
will likely be a piece of the puzzle needed for an active weather
day given the questionable instability and inhibition.

The NBM is still honing in on late Monday through Tuesday as the
best potential for showers and thunderstorms across eastern and
central Arizona, but confidence in this is still fairly low. It
would not be surprising to have any day from Monday through
Thursday to be a good storm day, but it is still too early to
pinpoint which day or days. With the upper level support leaning
toward being less of an influence, we may just have to rely on
differential heating and/or wherever the western edge of the
moisture axis sets up. Forecast instability does look to be enough
to support some strong storms and with the moisture levels
expected, heavy rainfall leading to localized flooding could also
become an issue. Overall, rain chances for next week look quite
conditional and PoPs are likely to change. Forecast temperatures
for next week have also been trending upward over the past few
days with decreasing chances of having lower desert highs dipping
below 100 degrees on any day. The latest NBM shows highs hovering
right around normal to a few degrees above.

&&

.AVIATION...Updated at 1000Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:

The only weather issue will be low confidence on wind directions
this morning and timing of a later than usual SW/W wind shift this
afternoon, under FEW-SCT mid and high cloud decks. In the wake of
an outflow that moved through last night, winds have settled out
of primarily easterly directions, however, as speeds relax AOB 6
kts early this morning, anticipate some periods of variability. A
later than usual shift to west winds is anticipated this
afternoon, with some guidance even suggesting a prolonged period
of southerly variability midday into the afternoon. Overall, the
wind pattern today and tonight should return to familiar diurnal
tendencies.

Southeast California/Southwest Arizona including KIPL and KBLH:

Winds will continue to favor SE at KIPL and SSE to SW at KBLH.
Speeds will remain generally between 6-14 kts with gusts at KBLH
this afternoon and this evening in a 20-25 kt range. Mostly clear
skies will prevail other than periods of FEW high cirrus.

&&

.FIRE WEATHER...
Slight chances for showers and thunderstorms can be expected
through the weekend, with the best chances over the Arizona high
terrain. Chances are expected to increase across the eastern
districts early next week. MinRHs through early next week will
generally be hover close to 15-25% for the far western districts,
while higher values closer to 25-35% will be seen elsewhere. Winds
will somewhat follow typical diurnal patterns, but with more of a
south southwesterly predominant wind across the western districts.
Daily afternoon gusts of 20-25 mph will be common across the
Lower CO River Valley this weekend before becoming more widespread
early next week.

&&

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

$$

SHORT TERM...Kuhlman
LONG TERM...Kuhlman
AVIATION...Whittock
FIRE WEATHER...Kuhlman