404
FXUS65 KPSR 181712
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1012 AM MST Thu Dec 18 2025

.UPDATE...Updated 18z Aviation Discussion...

&&

.KEY MESSAGES...

- Dry and tranquil weather conditions with well-above normal temperatures
  will prevail across the region into early next week.

- A change in the weather pattern is expected mid and late next
  week with cooler temperatures and potentially increased
  precipitation chances.

&&

.SHORT TERM /TODAY THROUGH FRIDAY/...
A strong upper-level high pressure sitting over the eastern
Pacific will continue to promote dry and tranquil weather
conditions across the Desert Southwest. Under the influence of the
ridge, afternoon high temperatures will continue to run a good
10-13 degrees above seasonal norms for mid-December as readings
top out in the mid to upper 70s, with areas around the Imperial
Valley reaching into the low 80s. As the center of the upper-
level high shifts eastward on Friday, 500 mb height fields will
rise slightly, promoting warmer afternoon highs across central
Arizona as highs top out in the upper 70s to near 80 degrees.

&&

.LONG TERM /SATURDAY THROUGH LATE NEXT WEEK/...
Upper-level ridging will continue to persist across the Desert
Southwest throughout the weekend and early next week, continuing
the dry and tranquil weather pattern. Temperatures will continue
to remain unseasonably warm throughout this period with afternoon
highs across the lower deserts ranging between the upper 70s to
low 80s, which will be a good 10-15 degrees above normal for this
time of the year. In fact, there is a high probability (>70%) of
Phoenix breaking record highs, especially by Sunday and Monday,
according to the latest NBM.

Model guidance continues to show a pattern change heading towards
the middle and latter portion of next week as the upper-level
ridge moves eastward into the southern Plains, allowing a deep
Pacific trough to build off the West Coast. Examining the ensemble
cluster analysis, there continues to be large spread in the
overall strength and positioning of the trough. Nevertheless, the
ensembles show abundant moisture spreading into the region out
ahead of the troughing feature late Tuesday into Wednesday with
IVT values forecast to exceed 250 kg/m/s. This increasing moisture
will promote precipitation chances beginning next Wednesday, with
the highest chances across the western deserts. Precipitation
chances may continue through the end of next week, however, this
will all be dependent on the overall strength and positioning of
the trough. Given that this will be a warm weather system, all of
the precipitation, even across the higher terrain, should fall as
rain. With the increasing clouds and precipitation chances, along
with decreasing heights aloft, temperatures mid to late next week
are expected to cool down but will likely still remain above
normal.

&&

.AVIATION...Updated at 1712Z.

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

No aviation weather concerns under some passing high cirrus cloud
decks can be expected throughout the TAF period. The overall wind
pattern will continue to exhibit light and diurnal tendencies
with extended periods of variable to even calm conditions,
especially at KSDL, KIPL, and KBLH.


&&

.FIRE WEATHER...
Persistent high pressure across the region will continue to
promote dry and tranquil weather as well as unseasonably warm
temperatures, 10 to 15 degrees above normal, into early next week.
Winds will generally be light and follow familiar diurnal
patterns. Afternoon MinRHs will range between 20-30% with good
overnight recoveries of 40-70%.

&&

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

$$

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

NWS Phoenix (PSR) Office