422
FXUS65 KPSR 131711
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1010 AM MST Sun Sep 13 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 part of the week, especially over mountain
locations.

- Although uncertainty remains, there will be potential for some
storms to produce strong winds and heavy rainfall over the next
several days.

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

&&

.SHORT TERM /Today through Monday/...
The main forecast concern early this week (and even through the
middle of the week) will continue to be the conditional
probabilities of thunderstorms across the area, some of which could
produce localized strong winds, blowing dust, and heavy rainfall.
The subtropical ridge continues to give way to broad upper level
troughing building in across the Northwestern U.S. By Monday, the
ridge center is forecast to be positioned over the Southeastern U.S.
with the broad troughing filtering more into our region and likely
staying there for much of the week. At least the eastern half of
Arizona will remain well positioned much of this week for periodic
influxes of moisture out of northern Mexico and off the Gulf of
California. Moisture levels are expected to remain very adequate for
shower and thunderstorm potential over the next several days with
the main limiting factors being the overall weak upper level support
and weak to moderate convective inhibition.

Saturday`s showers and storms overachieved compared to forecast
guidance, just like Friday. Models have had a difficult time with
depicting storm potential in this somewhat conditional environment
and under a southwesterly steering flow. Unfortunately, this is
likely to be the case for today and probably most days for the
coming week. Our expectations is for today and Monday to at least
have a 2 or 3 periods of showers and isolated thunderstorms with the
CAMs favoring late this afternoon/early evening, Monday morning and
again later Monday. We should have plenty of insolation today
resulting in modestly high CAPE of 1000-1500 J/kg with little CIN
later in the afternoon into the evening. Although CAMs really can`t
agree on convection for today, it is logical for storms (some
potentially strong) to develop with a focus over higher terrain
areas. Chances into the south-central Arizona lower deserts are
expected to be more limited, but PoPs have been adjusted upward to
at least include 10-15% chances for eastern and northern portions of
the Phoenix metro.

After a brief reprieve in rain chances later this evening/early
tonight, a couple HREF members are pointing at a round of elevated
showers and embedded thunderstorms at some point between 3 AM-10 AM
Monday. The more likely time frame for this type of convection
should be a couple hours before sunrise before gradually diminishing
shortly after sunrise. Given the expected elevated nature of these
potential showers and storms, we should only expect localized heavy
rainfall as the only threat. For the latter half of Monday, the best
potential for showers and storms should be over southeast Arizona
and potentially into the higher terrain east of Phoenix. Given the
forecast CAPE values of up to around 1500 J/kg and very respectable
low level mixing ratios of 13-14 g/kg, this should present a heavy
rainfall and localized flood threat into southern Gila County later
Monday.

&&

.LONG TERM /Tuesday through Saturday/...
The weather pattern through at least the middle of the week will
continue to support good moisture levels over at least the eastern
half of Arizona and likely improved upper level ascent for Tuesday-
Thursday. Tuesday may involve a brief period of drier air moving
into south-central Arizona from the southwest and this shows up in
the fairly limited PoPs Tuesday afternoon/evening. However, NBM
guidance shows a resurgence of moisture and rain chances during the
overnight hours Tuesday night/Wednesday morning. Chances Wednesday
into Thursday are also looking better with a potential disturbance
tracking northward into central/eastern Arizona at some point.
Needless to say, the model differences call into question the best
timing for rain chances and the exact areas, but as long as the
upper level support and good moisture remain present chances will
remain elevated.

WPC has added a slight risk on the Days 2-4 (Monday- Wednesday)
Excessive Rainfall Outlooks over the eastern Arizona high terrain.
It would not be surprising for subsequent issuance`s of the EROs to
extend the risk through Thursday or even Friday depending on the
forecast available moisture. Although the risk for heavy rainfall
and flooding will be present through at least the middle of the
week, the risk for strong downdraft/outflow winds is likely to
decrease with guidance showing decreasing forecast DCAPEs. Models
are still trending toward drier air finally moving eastward through
most of Arizona by Friday or Saturday. This should mostly shut down
rain chances over the lower deserts and decrease chances over higher
terrain areas.

Temperatures throughout the entire week are expected to remain
fairly close to seasonal normals with the lowest forecast highs
occurring on Tuesday and Wednesday. As long as models are correct
with the drying trend late in the week into next weekend,
temperatures are favored to drift back to above normal with highs
more in a 103-108 degree range by Friday or Saturday.

&&

.AVIATION...Updated at 1710Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Very low confidence forecast through Monday given vast uncertainty
in thunderstorm development/coverage and resulting effects on winds
and flight categories. Confidence is good that an extended period of
southerly cross runway winds will exist early this afternoon before
becoming W/SW by late afternoon. Similar to yesterday, TSRA may
develop over terrain features with modest outflow winds and isold
BLDU around the airspace, but not directly impacting terminals
(chances less than 25%). However, its not out of the question for
westerly winds to be disrupted at some point this evening by effect
from storms.

Models still want to blossom SHRA/TSRA over/near the Phoenix metro
Monday morning around sunrise, though confidence in location and
coverage is low, and only justifying a Prob30 mention at this time.
If SHRA/TSRA indeed materialize, erratic wind directions and
potentially briefly lower flight categories will be possible through
mid/late morning. Trends in winds and additional convective
development the remainder of Monday will be highly contingent on
morning activity (or lack there of).


Southeast California/Southwest Arizona including KIPL and KBLH:
No weather concerns will exist through Monday afternoon under mostly
clear skies. Confidence is very good that winds will behave similar
to the past 24 hours varying between a SE and SW heading. Afternoon
gusts around 20kt will be common at KBLH.

&&

.FIRE WEATHER...
Chances for scattered showers and isolated storms will continue
today before increasing and becoming more widespread into the south-
central Arizona lower deserts beginning Monday. Moisture levels will
remain high enough to support localized heavy rainfall with any
storms. Minimum humidity levels over the next several days will only
fall into a 15-25% range in western districts and 25-40% in eastern
districts. This will follow fair to good overnight recovery of 40-
70%. Outside of thunderstorms, winds will generally remain light
with a southwest heading through nearly calm conditions will be
common in the morning hours.

&&

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

&&

$$

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