900
FXUS65 KPSR 121015
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
315 AM MST Wed Aug 12 2026

.UPDATE...Updated Aviation Discussion.

&&

.KEY MESSAGES...

- Better moisture and more favorable conditions for showers and
  storms are expected by this evening, lasting into Thursday
  morning.

- A Flood Watch has been issued for the high terrain across
  central and portions of eastern Arizona from late afternoon
  through tonight. Locally heavy rainfall will also be possible
  into the south-central Arizona lower deserts.

- Near to below normal temperatures are forecast through Friday
  before warming back up over the weekend into early next week.

&&

.SHORT TERM /TODAY THROUGH THURSDAY/...
Today and tonight are shaping up to be quite busy as the
subtropical ridge continues to shift eastward out of the region
while an upper level trough moves in from the west. The main
forecast concern will be the threat for heavy rainfall and
localized flooding mainly over the high terrain north and east of
the Phoenix area. A Flood Watch has been issued for all of Gila
County as well as over far northern Pinal and northeast Maricopa
Counties from late this afternoon through tonight.

The mostly over-turned atmosphere that resulted in lower
convective activity on Tuesday is recovering while increasing
south southwesterly flow today will help to pull even better
moisture northward throughout much of the area. The incoming
trough will provide the extra boost to pull moisture farther to
the north northeast, while also providing broad (albeit weak)
upper level forcing. The typical strong subsidence that holds back
convection from forming, especially over the lower deserts, will
disappear later this afternoon with forecast soundings showing
little to no CIN. The cooler daytime highs will however limit how
much instability that will develop with MUCAPEs mainly between
500-1000 J/kg from late afternoon into the evening hours before
dropping after midnight. Moisture levels will improve through the
afternoon hours with low level mixing ratios around 11 g/kg over
the lower deserts to as high as 12-14 g/kg over the high terrain.
A south to southwest steering flow will also increase to around
10-15kts by this evening, but that is not fast enough to prevent
heavy rainfall from occurring.

Latest hi-res CAMs are in good agreement showers and storms will
begin to develop over at least the high terrain mid to late
afternoon and then even over the lower deserts by early evening.
The generally uncapped atmosphere should allow for good areal
coverage of showers and storms during the evening hours with the
best area of focus across northern Maricopa County into Gila
County. Additional pockets of showers and storms are expected
with some guidance hitting La Paz County and over the lower
deserts of Maricopa and Pinal Counties. The activity is likely to
be more short-lived, but some redevelopment will remain possible
throughout the evening hours. This area will need to be watched
for a potential expansion of the Flood Watch. The main concern for
heavy rainfall potential stems from a high likelihood of
localized rainfall rates of 1-2"/hr and training of storms as
depicted by the CAMs over the high terrain just to the north and
east of the Phoenix. The activity is likely to continue past
midnight before winding down and gradually pushing to the east by
around sunrise Thursday morning. Additional isolated showers and
thunderstorms will again be possible Thursday afternoon, but with
the atmosphere drying out and forcing waining there will be very
little chance of any localized heavy rainfall.

Temperatures will fall further today into Thursday, especially
over eastern and central Arizona. NBM forecast highs for the
Phoenix area show upper 90s to around 100 degrees both days with
highs more in a 100-104 degree range across the western lower
deserts where mostly dry conditions will prevail.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Dry air will continue to spread northeastward through Arizona on
Friday with low level mixing ratios dropping to around 8 g/kg over
the lower deserts to 9-10 g/kg over the eastern Arizona high
terrain. These moisture levels during the summer monsoon season
typically prohibit convection across the area with at most a
10-20% chance of isolated showers or weak storms across the far
eastern Arizona high terrain. However, even with the drying
conditions surface dew points well into the 50s will still keep
that slight muggy feeling in the air. The trough will continue to
influence the region through Friday keeping temperatures a few
degrees below normal under partly cloudy skies.

Saturday looks to be quite similar to Friday with periods of
higher clouds persisting, but temperatures will begin to tick
upward again as the subtropical high begins to nudge back into our
region. Guidance shows H5 heights gradually rising into a
592-595dm range by early next week, or back to around the 90th
percentile of climatology. Moisture levels look to stay fairly
steady for the rest of the weekend into early next week keeping at
most low grade monsoon storm chances in place. The increased
heights and somewhat dry conditions will help to push daytime
highs to above normal by Monday with readings right around 110
degrees for next Monday and Tuesday.

&&

.AVIATION...Updated at 1015Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Main forecast challenge over the next 24 hours will be timing out
VCSH/VCTS at terminals. Best potential looks to be late this
afternoon and this evening, but there is also low confidence for
some spotty high-based showers or an isolated TS this morning.
Light winds AOB 7 kts will prevail this morning, with a tendency
towards SE, before a SW/W switch occurs later this morning.
Another period with westerly gusts 15-20 kts will be possible this
afternoon into the evening. Confidence is moderate that VCSH/TS
conditions will develop around the Phoenix airspace the terminals
late this afternoon and/or this evening, resulting in gusty,
erratic winds. FEW to SCT mid and high clouds will be common
through the TAF period with lowest bases down to 8K ft AGL late
this afternoon and this evening.

Southeast California/Southwest Arizona including KIPL and KBLH:
There will be a slight chance (10-20%) for VCSH/VCTS at both
terminals later today, mainly between 22-01Z at KIPL and 23-03Z at
KBLH. Otherwise, a typical SW-SE wind component will prevail
through the TAF period. Wind speeds up to 7-12 kts will be common
at both terminals with gusts up to 20-25 kts at KBLH during the
afternoon. FEW to SCT clouds will be common over the area with
lowest bases down to around 10K ft AGL.

&&

.FIRE WEATHER...
Elevated humidity levels, cooler temperatures, and good chances
for wetting rains are anticipated through Thursday morning over
at least the eastern districts. The best rain chances will be
during the evening and overnight hours tonight with lingering
chances through Thursday afternoon. Afternoon MinRHs will range
between 25-35% across the lower deserts and 40-50% for the
eastern high terrain, while overnight recoveries will remain
excellent. Winds will predominately be out of the south southwest
much of the period with the exception of any modest outflows from
thunderstorm activity. Drying conditions will move into the
region Friday and through the weekend dropping MinRHs to between
15-25% while temperatures gradually rise back to above normal.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Flood Watch from this afternoon through late tonight for AZZ541-
     545-547-549-552-555>558-560>563.

CA...None.
&&

$$

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