270
FXUS65 KPSR 161150
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
450 AM MST Wed Jul 16 2025

.UPDATE...Updated 12z Aviation Discussion.

&&

.KEY MESSAGES...

- Chances for scattered showers and isolated thunderstorms will
  continue through Thursday with the best chances likely focused
  over higher terrain areas.

- Drier conditions by the weekend should limit any rain chances to
  the eastern Arizona high terrain.

- Temperatures will dip to below normal today and last through
  Thursday before gradually warming back into the normal range
  starting Friday.

&&

.SHORT TERM /Today through Thursday/...
Shower and thunderstorm activity yesterday pretty much fell in
line with what the hi-res guidance was showing with the bulk of
the activity across southeast Arizona and over the Arizona high
country. Moisture was still quite limited over the lower deserts
and any activity that tried to reach near Phoenix died out. A
modest outflow from southeast Arizona did however bring a surge of
low level moisture through Pinal and Maricopa Counties with
surface dew points now in the 60s. Southeasterly flow in the mid-
levels through this afternoon will continue to advect moisture
northwestward, likely eventually reaching the CO River Valley. At
the same time, southerly flow in the lower levels across far
southwest Arizona will be importing drier air into our area.

Model guidance seems to have finally caught on that the abundant
cloud cover and cooler temperatures will hamper instability today
into Thursday. We may be able to manage a pocket or two of MUCAPEs
around 500-750 J/kg, but overall instability is expected to be
limited and thus the thunderstorm threat now looks to be fairly
limited. For today, the latest thinking is a remnant MCV near
Tucson and the cloud cover will likely suppress convection for
much of today across south-central Arizona, while the higher
terrain likely experiences another round of scattered
thunderstorms this afternoon into early this evening. Guidance
then suggests a weak PV anomaly will move northwestward through
southern Arizona this evening while we continue to see some
difluence aloft from the upper low to our southwest. Hi-res CAMs
show an area of showers developing across south-central into west-
central Arizona later this evening and during the overnight
hours, but due to the lack of instability only some embedded
thunderstorms are likely to be possible. Any thunderstorms today
should be fairly weak with little to no threat of any strong
winds and only a very marginal threat of localized heavy rainfall.
This area of rain may last into Thursday morning before it lifts
northwestward out of our area.

Both the GEFS and the EPS now fully support fairly strong drying
occurring later in the day Thursday, but it remains to be seen
whether we will see anything other than higher terrain isolated to
scattered showers and storms. We can`t rule out some convection
across the lower deserts Thursday afternoon, but the chances are
likely lower than what the NBM is depicting. Either way, even if
we do see activity on Thursday, there really doesn`t seem to be
much of a threat for gusty winds or heavy rainfall. We have dialed
back the NBM PoPs, but maybe not quite enough.

On a positive note, the increased moisture and clouds will
definitely help to hold down temperatures through Thursday. The
latest NBM forecast highs show readings topping out only in the
upper 90s to around 100 degrees in the Phoenix area to as warm as
100-105 degrees across the lower deserts of southeast California
and far southwest Arizona.

&&

.LONG TERM /Friday through Tuesday/...
The upper level low is forecast to move northward Thursday into
Friday likely reaching southern California during the daytime
hours Friday. Dry air is currently wrapping around this low and as
it moves into our area, this dry air will add to the already
drying conditions. As PWATs drop to around 1.1-1.3" on Friday, the
chances for rain will continue to diminish. We may be able to
squeak out some isolated showers or a weak storm or two across
southwest Arizona and south-central Arizona, but PoPs are mostly
below 20%. Lingering moisture over the Arizona higher terrain
should allow for some afternoon scattered showers and isolated
thunderstorms, but we are not expecting much from this activity.

Temperatures will also begin to warm up starting Friday as we will
lose most of our cloud cover. Forecast highs Friday fall just
short of normals by a degree or two. Models are a bit uncertain
with how fast to kick out the upper level low, or even it does at
all, but they do agree it will weaken quickly Friday into
Saturday. By Saturday, the subtropical ridge centered over the
Southern Plains will begin to influence our region a bit more
helping to push temperatures back into the normal range.
Fortunately, the high is likely to stay displaced well to our
east through at least the first part of next week, so temperatures
are not likely to warm past normal levels. Moisture levels over
eastern Arizona may also stay high enough for some isolated
afternoon convection each day starting this weekend, but chances
over the lower deserts should mostly remain below 10%.

&&

.AVIATION...Updated at 1150Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
The primary aviation weather concerns through the period will be
lower than usual confidence on overnight/early morning wind
directions and the potential for VCSH/VCTS conditions. Showers
producing a few strikes of lightning are currently north of KDVT
and will pass east of the Greater Phoenix Area over the next hour
or so. Meanwhile, a slight chance (10-20%) for further scattered
shower development exists through early this afternoon as a
mesoscale low pressure system draws near from where it sits
currently near Tucson. Winds will tend to shift from SE or light
and VRB to SW/W by 17-19Z, with some afternoon gusts into the mid
teens possible. Tonight, have introduced VCSH to indicate the
potential for overnight scattered showers developing, with chances
for SHRA across the Greater Phoenix Area around 30-40%. Though
winds will likely maintain a W/NW configuration during the
overnight hours, nearby SHRA activity could produce brief erratic
behavior. SCT to BKN cloud decks AOA 8 kft will be common through
Thursday morning.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation weather concerns are expected throughout the TAF
period under mostly clear skies and gradually increasing coverage
of mid level clouds overnight into early Thursday morning. Winds
will generally be out of the east to southeast at KIPL and out of
the south at KBLH. Wind gusts upwards of 20-25 kts can be expected
at times once again Wednesday afternoon/evening, with the
strongest gusts mainly at KBLH.

&&

.FIRE WEATHER...
Increased moisture and cooler temperatures are expected through
Thursday with scattered showers and isolated thunderstorms
focused more over higher terrain areas. Drying conditions by
Friday will mostly end any chances across the lower deserts.
Afternoon MinRHs will only dip to between 25-30% for much of the
area today and Thursday before dropping closer to 20% by Friday.
Expect south southeasterly gusts of 20-30 mph today over the CO
River Valley before dropping off on Thursday with more diurnal
lighter winds over the eastern districts. Eventually, high
pressure is expected to return to the region by the weekend with
RHs dropping back into the teens, temperatures returning to near
normal, and rain chances ending for all but the higher terrain.

&&

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

$$

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