Chiriaco Summit, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

329
FXUS65 KPSR 240600
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1100 PM MST Tue Dec 23 2025

.UPDATE...Updated Aviation Discussion.

&&

.KEY MESSAGES...

- A Flood Watch and Wind Advisory will be in effect for the
  western, higher elevation portion of Joshua Tree National Park
  on Wednesday.

- A record high temperature for the date was set in Phoenix this
  afternoon.

- An unsettled weather pattern will carry us through the Christmas
  holiday and beyond, with gradually cooling temperatures and a
  couple periods of increased rain chances, one through tonight
  and another Wednesday afternoon into Thursday.

&&

.SHORT TERM /TODAY THROUGH THURSDAY/...
For the third day in a row, a record high temperature has been
broken at Phoenix Sky Harbor Airport. A temperature of 80F was
recorded at the site, which breaks the previous record of 79F
that was set in 1950.

The overall upper level pattern through Thursday will remain
rather stagnant, with a broad area of ridging centered over
TX/Gulf Coast states, and a longwave trough just off the West
Coast. Satellite- derived total precipitable water reveals a
couple features that will bring rain chances today/tonight and
again tomorrow night into Thursday: 1) the influence of an initial
shortwave currently moving inland and tapping tropical moisture,
promoting a band of showers over Southeast CA that will continue
eastward into South-Central AZ by the evening, and 2) a second
shortwave offshore rounding the base of the longwave trough that
is driving IVT values consistent with an atmospheric river and
will make landfall Wednesday, influencing the forecast area mostly
in the PM hours into Thursday morning.

Total rainfall accumulations with this initial round of showers are
expected to be on the light side with the latest QPF from WPC
showing most of the lower deserts receiving anywhere from a trace to
a couple tenths of an inch, whereas the foothills and higher terrain
areas north and east of Phoenix should observe locally higher
amounts upwards of 0.30-0.40" thanks to the orographic enhancement.
Some automated rain gauges in southeast CA have already reported on
the order of 0.05" with the passage of the initial band of showers.

The initial shortwave will exit the region Wednesday morning. In
its wake, GFS bufr soundings indicate notable midlevel drying and
subsidence, ending rain chances temporarily for all areas but the
mtns/southward facing slopes north and east of Phoenix, where
scattered light showers may continue through the day. Attention
then turns to the aforementioned second shortwave, which models
have consistently advertised driving IVT values in excess of 500
kg/ms onshore along the LA/San Diego areas Wednesday morning and
continuing inland into the Desert Southwest Wednesday PM into
Thursday. An attendant upper level jet with this second shortwave
will also promote breezier conditions and better forcing for
precipitation. Though previous events prove the powerful impact of
"rain shadowing", even over interior mountain ranges of Southeast
CA, sufficient evidence existed to hoist a Flood Watch for the
mtns/higher elevations of Western Joshua Tree National Park.
Antecedent moisture brought into the region with this initial
shortwave, coupled with jet dynamics and significant inland
penetration of 250-500 kg/ms IVT values with the second shortwave
should provide a window Wednesday afternoon for sustained moderate
rainfall rates. HREF probabilities for >1" of rain over the
mountains of far western JTNP are between 40-80%, and WPC QPF
shows 0.8-1.65" totals. Meanwhile, similar HREF probabilities for
wind gusts in excess of 40 mph in the same area justified a Wind
Advisory Wednesday mid morning through the early evening.

Afternoon high temperatures both Wednesday and Thursday will remain
above normal in the low to mid 70s. However, the bigger story will
be the overnight low temperatures as given the highly anomalous
moisture and abundant cloud cover that will be in place, readings
will be quite warm for late December, in the upper 50s to around 60
degrees and potentially break record warm lows across all three
climate sites (Phoenix, Yuma, and El Centro).

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
By the end of the week and into the weekend, as the main trough
axis pushes onshore across the western CONUS, the latest guidance
now shows the base of the trough splitting off into a closed low
off the southern CA coast in what is expected to develop into a
rex blocking pattern across the West Coast. However, guidance then
diverges significantly in the overall positioning of the closed
low as this blocking pattern matures. Both the CMCE and EPS show
the closed low becoming positioned well offshore with most of the
Desert Southwest under strong ridging, while the GEFS positions
the closed low much closer to the coast. The CMCE and EPS solution
would keep the region dry through early next week whereas with
the GEFS solution, subtropical moisture will be pulled into the
region, resulting in increased precipitation chances once again as
early as Sunday and continuing into early next week.

Temperatures heading into the weekend are expected to slightly
cool off even more from the readings mid and late week with most
of the lower desert communities likely stuck in the mid to upper
60s for afternoon highs, which would be close to seasonal norms
for late December. A slight warming trend closer to 70 degrees
will be possible heading into early next week, depending on the
overall pattern evolution.

&&

.AVIATION...Updated at 0559Z.

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

SHRA and lowered CIGs through the overnight hours will be the
primary aviation weather issues during the next 24 hours. Light
shower activity continues to push across parts of the Phoenix
metro this evening and will continue into the overnight hours.
CIGs will lower during this time to at least 7-8k ft, and perhaps
as low as 5-6k ft at times. Model probabilities of CIGs <6k ft
are only around 10%. There also may be FEW to SCT lower clouds
down to 3k ft around mountain features. Showers should diminish by
15-17Z with SCT to BKN 7-8k ft clouds persisting throughout the
rest of the day. Winds through the TAF periods will predominantly
favor the east with speeds mostly aob 10 kts and periods of
variability.

Southeast California/Southwest Arizona including KIPL and KBLH:

Shower activity has mostly diminished across southeast California,
however, lower CIGs will continue into the overnight hours. CIGs
down to around 6-7 kft are expected through tomorrow morning.
Winds will predominantly favor the E-SE at KIPL, while winds will
favor the E-NE at KBLH before switching around to the south late
Wednesday morning. Expect periods of light and variable winds to
occur at both terminals throughout the period.

&&

.FIRE WEATHER...
An unsettled weather pattern is expected to develop across the
region beginning today and lasting through the end of the week,
bringing higher moisture, increased rain chances, and cooler
temperatures. A strong moisture push will spark scattered shower
activity beginning this afternoon across the western districts,
pushing into south-central AZ later this evening. Another round
of rain is expected between Wednesday afternoon and Thursday
morning. MinRHs today will range between 20-25% across the eastern
districts to 35-50% across the western districts with excellent
overnight recoveries of 75-100%. MinRHs will then jump in the
45-70% range Wednesday through end of the week before slightly
decreasing over the weekend with excellent overnight recoveries of
75-100% continuing. Winds will remain light today with breezes
picking up on Wednesday, especially across the western districts,
with some periodic gusts in excess of 20 mph. Lighter winds are
anticipated by the latter portion of the week.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...Wind Advisory from 8 AM to 6 PM PST Wednesday for CAZ560.

     Flood Watch from 9 AM PST Wednesday through Wednesday evening
     for CAZ560.

&&

$$

SHORT TERM...Whittock
LONG TERM...Lojero
AVIATION...Smith
FIRE WEATHER...Lojero