648
FXUS65 KPSR 061741
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1041 AM MST Sun Sep 6 2026

.UPDATE...18Z Aviation Discussion

&&

.KEY MESSAGES...

- Aside from some light shower chances across Joshua Tree National
  Park today mostly dry and quiet weather conditions are expected
  through the first half of this week.

- Thunderstorm chances will start to increase, mainly across
  south-central and eastern Arizona, by the latter half of the
  upcoming workweek.

- Temperatures will be near to around 5 degrees above normal
  through the upcoming week.

&&

.SHORT TERM /TODAY THROUGH TUESDAY/...
Early this morning reveals that the overall synoptic pattern remains
largely unchanged with the omega block in tact. The ridge of high
pressure remains in place across the central US with troughing along
both coasts, with the low pressure centers over the Pacific NW and
New England. Hurricane Marie also continues to spin well off the
coast of the Baja Peninsula. This pattern continues to support
mid and upper level moisture advection into the region, with the
highest moisture content across SE CA and SW AZ. This can be seen
on the SPC Mesoscale Analysis, where PWATs are around 1.5-1.7"
across SE CA and SW AZ. This forcing, in combination with the
increased moisture, is resulting in some light shower activity,
for our CWA, mainly across eastern Riverside County. The SPC
Mesoscale Analysis also shows little to no CAPE, so no
thunderstorm activity is expected. Throughout the day today, the
high will begin to retrograde westward with the trough across
western CONUS beginning to lift northeastward. Additionally,
Hurricane Marie will continue to move northwestward. The
combination of these three things will result in the better
moisture plume moving northwestward. So, the best shower chances,
for our CWA, today will be confined to Joshua Tree National Park.
There will be little to no instability so no thunderstorms are
expected. Little to no rainfall accumulations are also expected.
The best rainfall today will be north of our CWA into San
Bernardino County in CA, into the Las Vegas area, and NW AZ. With
the shower activity across this region, outflow winds from the
northwest are expected to impact much of the lower deserts during
the afternoon and early evening, with peak gusts of 20-30 mph
likely.

Heading into the beginning of the workweek, the subtropical high
will continue to retrograde westward. H5 heights over our area will
go from 588-591 dm today to 591-594 dm for the beginning of the
workweek. This will result in a return of southwesterly flow which
will bring in drier air. PWATs will decrease to 1.3-1.6" area
wide. In addition to the decrease in moisture, with high pressure
moving back in dry and quiet conditions are on tap to start the
workweek. Temperature wise, with high pressure building back in
temperatures will increase slightly through Tuesday. For areas
across SE CA they should see temperatures a couple degrees below
normal today due to the increased cloud cover from the increased
mid and high level moisture. Otherwise, lower desert afternoon
high temperatures are forecasted to be in the 100-108 degree range
and for the higher terrain, in the 92-102 degree range.
Temperatures of this magnitude are around 2-4 degrees above
normal, which results in Minor to Moderate HeatRisk area wide.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Heading into the later half of the workweek, ensemble model guidance
has come into slightly better agreement on the overall synoptic
pattern. The models have come into better agreement on the placement
of the features, but still differ on the overall strength of the
features. Both the GEFS and the EPS show a shortwave trough across
norther CONUS and southern Canada, a broad subtropical ridge
stretching across much of the lower 2/3 of CONUS, along with a
closed low off the coast of northern California. The EPS continues
to be the stronger solution, with a stronger closed low in the
Pacific and a stronger subtropical high. These changes can be seen
in the now slightly smaller temperature spread in the NBM
interquartile range, however, the spread remains large enough (5-7
degrees) that you can tell the models are still in some
disagreement. The GEFS show the high at peak strength (H5 heights of
594-597 dm) during the middle of the week before weakening (H5
heights of 591-594 dm) and moving overhead on Thursday. The high
looks to continue to weaken (h5 heights of 588-592 dm) heading into
the weekend. So temperatures are forecasted to remain slightly above
normal during the middle of the week before beginning a slight
cooling trend to slightly below normal for the end of the workweek
and into the weekend.

As for shower and storm chances, the ensemble members continue to
show those chances starting to increase, for at least portions of
the CWA, beginning on Wednesday. PWATs look to increase to around
1.5-1.9" for the latter half of the week, so moisture should not be
a limiting factor. With the high forecasted to move overhead on
Thursday, rain chances will likely be limited to the higher terrain
areas across eastern Arizona on Wednesday and Thursday. Rain chances
may extend into the lower deserts of south-central Arizona heading
into the weekend. However, the current WPC PoPs of 30-50%, for
Friday into Saturday, seem rather aggressive, especially this far
out. WPC`s Saturday PoPs of 10-30% seem more reasonable.

&&

.AVIATION...Updated at 1741Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
The main weather concern will be gusty winds later this evening.
Winds will maintain a westerly component throughout the period
with winds shifting out of the NW by 23Z-00Z where gusts will
also begin to ramp up. KPHX and KDVT can expect gusts between
20-25kts between 23Z-04Z, while elsewhere may also experience
brief periods of gusty conditions but not enough to warrant
inclusion in the TAF. Tomorrow morning is expected to have some
VRB conditions but should still maintain a mostly westerly
component.

Southeast California/Southwest Arizona including KIPL and KBLH:
Thick mid/high cigs with at most virga/sprinkles will persist
through this evening, albeit with little to no operational impact.
Confidence remains high that NW winds with gusts between 20-25kts
will develop mid/late this afternoon.

&&

.FIRE WEATHER...
Temperatures will be slightly below normal across SE CA today.
Otherwise, temperatures will be near to slightly above normal
through the workweek. Rain chances today will be confined to
Joshua Tree National Park, with chances for wetting rainfall very
low. MinRH`s will be around 20-30% area wide through much of this
upcoming week with good overnight recovery. Some elevated
afternoon/early evening breeziness out of the northwest is
expected today with peak gusts of 20-30 mph. A more typical
diurnal wind pattern with some occasional afternoon upslope
breeziness can be expected through much of this coming week.

&&

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

$$

SHORT TERM...Berislavich
LONG TERM...Berislavich
AVIATION...Ryan
FIRE WEATHER...Lojero/Berislavich