255
FXUS65 KPSR 121123
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
423 AM MST Mon Oct 12 2026

.UPDATE...Updated 12z Aviation Discussion..

&&

.KEY MESSAGES...

- Periods of isolated showers will continue today into tonight
  before coming to an end Tuesday morning.

- Temperatures will continue to cool through Tuesday with highs
  dipping into the seventies, while overnight lows easily reach
  into the fifties for Tuesday and Wednesday.

- Dry weather will settle in by Wednesday before breezy to windy
  conditions return later in the week while temperatures slowly
  return to near normal.

&&

.SHORT TERM /TODAY THROUGH TUESDAY/...
Deep troughing remains situated across much of the Western U.S.
with H5 heights below the 10th percentile of climatology from
Oregon through southern California. The low center is currently
situated across eastern Oregon with the trough axis extending
southward through central California. Strong southwesterly flow
remains in place across the Desert Southwest, gradually pulling in
drier air aloft. Despite the drying, there is still very adequate
moisture in the low levels with mixing ratios at around 10 g/kg.
This moist layer is expected to stick around through a good
portion of today allowing for upslope flow to generate periods of
showers across the area. Although instability is quite low at
100-200 J/kg, some of the current shower activity is showing
modest reflectivities and efficient rainfall rates of over 1" per
hour. A few spots have recorded a quick 0.25" of rain since
midnight over far western portions of the Phoenix metro and into
northern Yuma and southern La Paz Counties. However, these higher
rainfall rates are not expected to last much past sunrise as drier
air working in from the southwest will gradually push mixing
ratios closer to 8 g/kg over south-central Arizona later this
morning to as low as 5-6 g/kg across the western lower deserts.

Hi-res CAMs have been consistent in showing isolated shower
activity lasting through most of today with a gradual eastward
shift in the activity. Some lower desert locations could receive
another few tenths of an inch today, but most will see very little
due to the isolated nature of the showers. The highest rainfall
amounts of 0.25-0.50" are likely to fall across the foothills of
northern Maricopa County into the high terrain northeast of
Phoenix. The trough axis and a weak cold front are slated to move
through the area this evening into tonight potentially leading to
a broken line of showers, but by that point the drier air
advecting in from the southwest will be an even bigger hindrance
for rainfall. Any lingering shower activity tonight into Tuesday
morning should mostly be focused over the eastern Arizona high
terrain.

As even drier air surges through the area from west to east on
Tuesday, skies are expected to become clear to mostly clear west
of Phoenix to partly cloudy from Phoenix eastward. We can`t rule
out some additional light showers well east of Phoenix through
Tuesday afternoon, but little additional rainfall is expected.
Temperatures today will struggle to top 80 degrees across the
lower deserts with even cooler air on Tuesday limiting highs to
mostly the mid 70s.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As we transition into a drier weather pattern mid week, we will
still have to deal with periods of breezy to windy conditions.
The upper low is forecast to move east northeastward from northern
Arizona into Colorado on Wednesday leaving a tight pressure
gradient across much of our area. This should bring increasing
northwesterly winds across southeast California and far western
Arizona early Wednesday likely peaking late Wednesday morning
before the gradient relaxes. Wind gusts of 25-30 mph can be
expected across much of the Lower CO River Valley Wednesday
morning into early afternoon.

Temperatures Wednesday will remain well below normal across the
area with a somewhat chilly start to the morning with lows in the
50s across the lower deserts to easily into the 40s for higher
terrain locations. Highs Wednesday should be very similar to
Tuesday, although some warming across the western lower deserts
may push highs back into the lower 80s.

Models are finally coming into better agreement for late this
week into the weekend showing shortwave energy and an upper level
jet max diving southwestward through the region on Thursday. At
the same time a strong upper level ridge just off the West Coast
will move inland. For now, it seems this set up will result in a
weak cut-off low forming somewhere to our southwest by Friday with
ridging settling in just to our north. To complicate things even
more, a polar air mass will quickly dive through the Plains States
Thursday potentially bringing a back-door cool front into eastern
Arizona Friday morning. Even though this is a complex pattern, it
really won`t amount to much for our area as dry air will remain
entrenched enough to keep rain chances below 10%.

However, it is looking increasingly likely a strong pressure
gradient will develop across Arizona by Friday leading to breezy
to locally windy easterly winds developing Thursday night into
Friday morning. NBM guidance does show the potential for Advisory
level winds, but from past experience these winds tend to be
overdone. We should at least expect occasional wind gusts of 25-35
mph to maybe some 35-40 mph possible across far southern Gila
County, Pinal County, into southern Maricopa County. These gusty
easterly winds will be more pronounced during the latter half of
the morning before diminishing some during the afternoon. Guidance
suggests a repeat of these gusty winds on Saturday before the
gradient begins to relax into Sunday. Moderating temperatures are
forecast for late week with highs warming into the 80s by
Thursday and likely staying at or just below normal through next
weekend.

&&

.AVIATION...Updated at 1120Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:

Gusty winds and periods of lower CIGs will be the primary issues
throughout the TAF period. Southeast winds early this morning will
veer out of the south by the mid-morning hours before veering
more out of the southwest by the afternoon hours. Peak wind gusts
upwards of 25 kts will be common starting mid-morning and continue
through the afternoon before subsiding after sunset below 10 kts.
Most of the day should remain dry with good confidence of VCSH
arriving by late this evening. CIGs as low as 6-7 kft with FEW-
SCT decks as low as 4 kft will be common throughout the period.
BKN CIGs as low as 4-5 kft will possible late this evening through
the overnight with the SHRA activity.

Southeast California/Southwest Arizona including KIPL and KBLH:

Gusty winds will be the main aviation weather issue throughout
the TAF period. Winds will predominately be out of the west at
KIPL and out of the southwest at KBLH throughout the period.
Winds will pick up by the mid-morning hours at KIPL and by the
early afternoon hours at KBLH with peak gusts upwards of 25 kts.
Gusts will subside after sunset. SCT-BKN cloud decks as low as 7
kft will be common throughout the period.

&&

.FIRE WEATHER...
Periods of isolated to scattered showers are expected through
tonight before a weak cold front moves through and drier air
begins to filter in on Tuesday. Elevated moisture levels will
keep MinRHs mostly above 40% through Tuesday before gradually
lowering into the latter part of the week. Today will bring some
afternoon breeziness with gusts up to 25 mph at times before
diminishing further on Tuesday. Below normal temperatures are
expected through at least the middle of the week. As the drier
conditions develop later this week, MinRH values will fall to
between 25-40% by Thursday. Thursday will also bring northerly
breezy to windy conditions across the western districts before
easterly breezy to locally windy conditions set up across at
least the eastern districts by Friday.

&&

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

&&

$$

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

NWS Phoenix (PSR) Office