091
FXUS65 KPSR 292341
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
441 PM MST Fri Aug 29 2025

.KEY MESSAGES...

- Temperatures for the Labor Day weekend will rise slightly above
  normal, leading to increasing widespread Moderate HeatRisk.

- Overall dry conditions will prevail through the weekend before rain
  chances gradually increase during the first half of next week.

&&

.SHORT TERM /Today through Sunday/...
We started off this morning with rumbles of thunder in some parts
of the Valley thanks to an outflow/gravity waves stemming from
convection down near the international border that acted upon
lingering mid-level moisture and instability. This allowed for
isolated to scattered showers and thunderstorms to develop across
central and eastern portions of the Valley, providing Phoenix Sky
Harbor with 0.01" while other areas saw upwards of around 0.25".
Drier conditions have since prevailed as dry westerly flow aloft
takes hold over the region, leading to mostly clear skies across
much of our area this afternoon as shown by the latest visible
satellite imagery.

Westerly flow aloft will persist into this weekend, allowing for
drier air to continue to be pulled into the region and dropping
PWATs near to below an inch. This will eliminate PoPs for most of
our area for the weekend outside of low end chances across the
southern Gila County high terrain by Sunday.

With drier conditions and plenty of sunshine prevailing across the
area this weekend, temperatures will rise slightly above normal for
the Labor Day weekend. NBM temperatures for Saturday show highs
topping out around 103-107 degrees across the lower deserts before
climbing to around 104-109 degrees Sunday. This will lead to
increasing widespread areas of Moderate HeatRisk for the holiday
weekend. If you have outdoor plans this weekend, be sure to stay
cool and hydrated.

&&

.LONG TERM /Monday through Thursday/...
As we turn our attention to next week, the overall synoptic pattern
will return to a more favorable pattern for monsoonal activity with
the high pressure being situated over the general Four Corners
Region, with easterly flow overhead. Guidance also shows a potential
inverted trough nearing or pushing into southern AZ as early as
Monday and potentially stalling out for a couple of days proving
some forcing for monsoonal activity. Monday may end up being more of
just a day for higher terrain activity with outflow boundaries
surviving into the lower deserts as the atmosphere works to bring in
better moisture (ensembles show PWATs decreasing to 1" or less this
weekend with westerly flow aloft) across the lower deserts to
support more showers and storms. However, a few showers and storms
would be possible if there were multiple colliding outflow
boundaries. PWATs will be on the rise through the middle of next
week with PWATs approaching 1.2-1.4" range Tuesday and 1.3-1.6"
range on Thursday. The EPS is running about 0.2" higher PWATs than
the GEFS. As for temperatures next week, we look to cool off back
below normal, especially if we have showers/storms that move through
and their associated cloud cover. There are still a lot of
unknowns for next week, but it could shape up to be quite active
if there is enough moisture available.

&&

.AVIATION...Updated at 2335Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation concerns are anticipated through the forecast period.
Light westerly winds will prevail this evening and through much of
the overnight period, with the exception of KIWA which should see
an easterly shift around 06Z-07Z. There will likely be a brief
period of easterly winds at KPHX Saturday morning before returning
out of the WSW around 17Z-18Z. Skies should remain mostly clear
aside from a few passing high clouds.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation concerns are expected through the forecast period
under mostly clear skies. Winds will remain W-NW at both terminals
overnight, becoming more northerly at KBLH early Saturday. Speeds
should remain aob 5 kts.

&&

.FIRE WEATHER...
Mostly dry conditions continue through the weekend with near 0%
chance of wetting rains. MinRHs today will mostly range between
15-20% this weekend. Winds will remain fairly light, with typical
afternoon breeziness, through the period while mostly following
typical diurnal trends. Temperatures this weekend will rise
slightly above normal with highs approaching 110 degrees for some
lower desert areas by Sunday. Chances for monsoonal activity will
increase again going into next week, with activity starting as
early as Sunday across the higher terrain in eastern Arizona.

&&

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

$$

SHORT TERM...Smith
LONG TERM...Berislavich
AVIATION...Salerno
FIRE WEATHER...Smith/Berislavich