925
FXUS65 KPSR 150539
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1030 PM MST Mon Sep 14 2026

.UPDATE...
Updated Aviation

&&

.KEY MESSAGES...

- Abundant moisture will remain situated across the eastern half of
Arizona providing enhanced chances for showers and thunderstorms
through the middle of the week, especially over the mountain
locations.

- There will be the potential for some storms to produce strong
winds, but the greater threat will be heavy rainfall and localized
flash flooding.

- Shower and thunderstorm chances will diminish by the end of the
week with the introduction of drier air.

- Near to slightly above normal temperatures are expected throughout
  the week.

&&

.SHORT TERM /Today through Wednesday/...
Latest objective analysis indicates the subtropical ridge of high
pressure centered over the southeastern states while broad upper
level troughing remains situated over the northwestern states. This
overall pattern configuration continues to support more of a south
to southwest flow across much AZ while more westerly flow, bringing
drier air, is occurring from the Lower Colorado River Valley
westward. The south to southwest flow entrenched across much of AZ
is expected to remain in place through the middle of the week,
aiding with periodic moisture influxes as PWAT values peak above
1.5" along with low-level mixing ratios of 12-14 g/kg. Therefore, an
elevated potential for shower and thunderstorm activity will remain
in place, especially from Phoenix eastward through the middle of the
week before chances diminish towards the end of the week once the
drier air filters in.

The combination of plentiful moisture and strong daytime heating
should result in good instability once again as MUCAPE values are
expected to peak at 1000-1500 J/KG. The latest HREF membership shows
southeast AZ becoming convectively active during the afternoon hours
with some of this activity drifting into the higher terrain areas to
the east and southeast of Phoenix with more isolated activity across
the south-central AZ lower deserts. Similar to the last couple of
days, despite the very favorable thermodynamic parameters in place,
the lack of good upper-level forcing for ascent continues to be a
limiting factor for more widespread activity. With these storms,
heavy rainfall leading to localized flash flooding will be the
primary threat with strong downburst wind gusts a secondary threat
given that DCAPE values will still be sufficiently high, ranging
between 1000-1200 J/KG. Quieter conditions can be expected this
evening into at least the first part of the overnight period, before
potentially another round of elevated showers and storms develops,
most likely after 3 AM MST. The latest hi-res guidance is indicating
the best potential over the foothills and higher terrain to north
and east of Phoenix. However, the convective threat late in the
overnight hours into early Tuesday morning will be highly
conditional of whether or not a gravity wave/outflow will be a
sufficient triggering mechanism for development as the overall
larger scale forcing for ascent will still be lacking.

Better upper-level support is more likely to materialize, especially
heading into late Tuesday through Wednesday, as a weak mid-level low
currently located over the southern tip of the Baja Peninsula in
conjunction with another weak upper-level low off the west coast of
the Baja Peninsula move into the region. Therefore, these features
are likely to pair up and be sufficient to trigger more widespread
shower and thunderstorm activity across much of central and eastern
AZ. Latest NBM is honing in on this increasing coverage as it shows
PoPs increasing to 50-80% from Phoenix eastward from Tuesday evening
through Wednesday. The main concern will be an increasing threat for
flash flooding given the abundant moisture in place with both the
ECMWF and GFS indicating PWATs exceeding 1.8" along with low-level
mixing ratios as high as 14 g/kg. In addition, MLCAPE values are
likely to range between 1000-1500 J/KG providing plenty of
instability. Therefore, the environment is likely to become
favorable for these thunderstorms to produce high rainfall rates in
excess of 1-2"/hr, leading to that enhanced flash flood potential. A
Flood Watch will likely be needed for portions of the area from late
Tuesday through Wednesday.

Temperatures through the middle of the week will continue to run
slightly above normal across the western deserts as high top out
around 105 degrees, while more clouds and potential rainfall will
keep highs closer to 100 degrees across the south-central AZ lower
deserts. In fact, with the greater likelihood of more abundant cloud
cover as well as higher rainfall potential, afternoon highs on
Wednesday across much of the south-central AZ lower deserts are now
forecast to top out in the 90s.

&&

.LONG TERM /Thursday through Sunday/...
Guidance is starting to agree on a quicker drying trend later this
week as the Pacific trough is favored to move farther into the Great
Basin and at least into northern and western portions of the Desert
Southwest. This is likely to push drier air eastward through most if
not all of Arizona as early as Thursday but more so Friday into
Saturday. Thursday is still a bit of an uncertain day as rain
chances may still linger across the south-central lower deserts and
definitely over eastern Arizona. However, by Friday, enough dry air
moving in should end chances over the lower deserts and really limit
chances over the high terrain. It is doubtful we will completely
scour out all of the moisture across the higher terrain, so 10-20%
PoPs remain each day across eastern Gila County through the weekend.

As conditions dry out into the weekend, temperatures are likely to
face a bit of a warming trend but as of now the region is favored to
stay under broad upper level troughing into the weekend. Lower
desert highs are expected to warm to above normal by Friday or
Saturday, but so far the NBM indicates a most likely range of 103-
107 degrees.

&&

.AVIATION...Updated at 0530Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
The potential for SHRA/TSRA and associated impacts will be the
primary weather concern through Tuesday night under frequent cloud
decks 7K ft and above. Confidence is good that E/SE winds will
prevail through the morning with the majority of SHRA/TSRA lifting
into higher terrain north and east of terminals. However, a few
SHRA/TSRA could redevelop near terminals prior to sunrise, and have
maintained a Prob30 mention.

Forecast confidence deteriorates Tuesday afternoon and evening
contingent on activity in the morning. Moderate confidence exists
that winds remain E/SE or become southerly during the afternoon with
any additional TS holding off until the evening. Development and
coverage of storms Tuesday evening remains highly uncertain, however
somewhat better confidence exists regarding more widespread
SHRA/TSRA and significant operational impacts late Tuesday night
into Wednesday morning.


Southeast California/Southwest Arizona including KIPL and KBLH:
No weather concerns will exist through Tuesday night under mostly
clear skies. Winds will continue to behave similarly to the past 24
hours varying between southeast and west at KIPL, and southerly
at KBLH with local afternoon gusts 20-25 kt.

&&

.FIRE WEATHER...
Periods of scattered showers and thunderstorms are likely through
Wednesday across the eastern districts supporting a localized heavy
rainfall threat. Moisture levels will remain elevated except for
southeast California. Expect minimum humidity levels to still fall
into a 15-25% range for the western districts while the eastern
districts will only dip to 30-45% through Wednesday. Winds will
generally follow diurnal patterns across the eastern districts,
while much of the western districts will have elevated southerly
winds with occasional gusts above 20 mph. By Thursday into Friday,
much drier air is forecast to spread eastward across the region,
eventually ending rain chances for all but the far eastern Arizona
high terrain and lowering humidities into the teens across the lower
deserts.

&&

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

&&

$$

SHORT TERM...Lojero
LONG TERM...Kuhlman
AVIATION...18
FIRE WEATHER...Kuhlman