285
FXUS65 KPSR 091728
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1028 AM MST Tue Dec 9 2025

.UPDATE...Updated Aviation Discussion.

&&

.KEY MESSAGES...

- Well above normal temperatures each day, with afternoon highs
  reaching 8-13 degrees above normal and potential for a few daily
  record highs in Phoenix.

- Dry and tranquil conditions will prevail for at least the next
  7 days.

&&

.SHORT TERM /TODAY THROUGH WEDNESDAY/...
Objective analysis and wv satellite imagery show a subtle dry
shortwave dropping south of AZ early this morning and strong high
pressure off to the west over the Pacific with a lot of moisture
cascading over the top of the high and through the PacNW and
Intermountain West. All this moisture will stay well to the north
of the Desert Southwest and the region will remain dry with clear
skies as the high to the west will not budge through the next
couple days. The large scale CONUS pattern resembles the textbook
La Nina atmospheric pattern.

With the dry pattern persisting over the next few days and higher
pressure in the wake of the shortwave trough, temperatures will
continue to gradually warm. Global ensembles show 850mb temps
going from 15C this morning to 18C Wednesday. This will result in
a few degrees of surface warming over the next few days. Highs
this afternoon across the lower deserts will reach the middle 70s
and then upper 70s to around 80 on Wednesday. Morning lows will
remain a bit chilly in the 40s to low 50s. These forecast highs
will be 8-13 degrees above normal and will even lead to Minor
HeatRisk in the Imperial Valley beginning Wednesday. Aside from
the warming temps and dry conditions, there will also be minimal
wind. This is the type of weather most here endure the summers
for!

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Afternoon high temperatures 8-13 degrees above normal will
continue through the long term forecast, peaking Thursday and
Friday when global ensembles show highest 850mb temperature
anomalies at around the 95th to 97th percentile. Latest forecast
highs from the NBM are also within a couple degrees of daily
records, including in Phoenix Thursday through Sunday. It is not
tremendously uncommon to reach 80 degrees this time of year, as
most daily records are around 80-85 degrees in December and
January. It is actually somewhat common for lower desert
communities to reach 80 degrees a few times each Dec-Jan, and it
has become more common during the last 10-20 years.

Heading through this weekend global ensembles show the large scale
pattern across the Southwest becoming flatter, with more westerly
flow, for at least a few days. This reduction in 500mb height
anomalies will result temperatures a smidgen cooler heading into
the beginning of next week, but still well above normal. Overall,
the long term outlook does not support a lick of rain. The desert
is gonna desert while this La Nina atmospheric pattern persists.

EXTENDED LOOK: Looking out at longer range models there is still no
sign of any significant weather pattern change. Ensembles maintain
positive height anomalies through week 2, which means a continuation
of above normal temperatures.  The NBM shows very little spread
in the temperature forecast (4 degrees max) through December 19th,
indicating a high confidence forecast. There is also no sign of
rain still. Global ensemble 90th percentiles do not show any
measurable precipitation until December 20th, which is not saying
much when the 90th percentile is mostly outliers. So, it may be
even longer before the next rain in the lower deserts.

&&

.AVIATION...Updated at 1728Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT; and
Southeast California/Southwest Arizona including KIPL and KBLH:

No aviation weather concerns will exist through Wednesday
afternoon under clear skies. Winds will continue to follow light,
diurnal tendencies with extended periods of variable or calm
conditions. Speeds will mostly remain aob 7 kts.

&&

.FIRE WEATHER...
Warm and dry weather will prevail across the region through this
week. Temperatures will be above normal and gradually warm to 8-13
degrees above normal by the end of the week. A dry weather system
toward the middle of next week may enhance winds. Otherwise,
winds will remain light every day and follow diurnal tendencies.
Humidities over the next week will stay above critical levels with
afternoon MinRHs mostly ranging between 20-25%, followed by good
overnight recoveries to around 50-70%.

&&

.CLIMATE...Daily Record Highs

   Phoenix
   -------
12/11  81 (1977)
12/12  79 (2010)
12/13  82 (2010)
12/14  78 (2010)
12/15  79 (1969)

&&

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

$$

SHORT TERM...Benedict
LONG TERM...Benedict
AVIATION...Smith
FIRE WEATHER...Benedict
CLIMATE...Benedict