034
FXUS65 KPSR 291145
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
445 AM MST Fri Aug 29 2025

.UPDATE...Updated 12z Aviation Discussion.

&&

.KEY MESSAGES...

- Near to slightly below normal temperatures today will warm to
around 5 degrees above normal this weekend, which will cause
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/...
Early this morning RAP analysis shows a ridge of high pressure over
New Mexico and southern Colorado, with a shortwave trough moving
through northwestern AZ. WV satellite imagery shows dry air quickly
filtering in behind the shortwave trough that is also helping to
push the cloud deck from yesterday east of our area. A few areas of
showers/virga have formed early this morning as the associated cloud
deck exits the area, most will stay dry. Mostly clear skies return
region wide by this afternoon. Afternoon high temperatures region
wide today are forecasted to be near to slightly below normal.
Temperatures will be near normal across south-central AZ and
slightly below in SE CA and SW AZ, however, they will be several
degrees warmer than yesterday across western portions of the CWA.

This weekend the subtropical ridge will build over the desert SW,
with heights aloft increasing to around 591 dm (up from 588 dm this
morning). With the increasing heights aloft we will also see
increasing temperatures. Afternoon high temperatures are forecasted
to climb above normal this weekend (in the 105-110 degree range
across the lower deserts). We will also see an increase in morning
low temperatures with lower deserts locations seeing morning lows
ranging from the upper 70s to mid 80s. This increase in temperature
will also cause our HeatRisk to increase into the moderate category
across the lower deserts.

Precipitation chances across the region look rather bleak this
weekend, with dry conditions continuing for most locations. By
Sunday, mid-level flow returns to easterly, which is more favorable
for monsoonal activity. However, this will only result in slight
chances (15-30%) for isolated showers and thunderstorms across the
higher terrain on Sunday afternoon and early evening.

&&

.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 1150Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Some early morning showers and thunderstorms over the central to
eastern portions of the metro pose as the main aviation impacts
through the period. The main impacts will be at KPHX and KIWA,
where conditions ranging from VCSH to -TSRA will be possible over
the next hour or so. After conditions improve going through the
morning hours, skies will gradually clear through the rest of the
period. Primarily westerly flow will be common at all terminals by
early to mid-afternoon, with a return to calm and variable or
light southeasterly overnight tonight.


Southeast California/Southwest Arizona including KIPL and KBLH:
No significant weather issues will exist through Friday night
under clear to mostly clear skies. Confidence is good that N/NW
winds will trend towards a light and variable character by
sunrise. Directions should favor a S/SW component later this
afternoon with limited gustiness.

&&

.FIRE WEATHER...
Dry conditions today and into the weekend will lead to warmer
temperatures and near 0% chance of wetting rains. MinRHs today will
mostly range between 15-25%, falling into the teens for the weekend.
Winds will remain fairly light through the period mostly following
typical diurnal trends. Temperatures will remain near to slightly
below normal today before rising to slightly above normal this
weekend. 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...Berislavich
LONG TERM...Berislavich
AVIATION...Young/18
FIRE WEATHER...Berislavich/Kuhlman