314
FXUS65 KPSR 172028
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
128 PM MST Wed Dec 17 2025

.KEY MESSAGES...

- Well above normal temperatures and dry conditions will persist
  across the region into at least early next week.

- A change in the weather pattern is expected during the latter
  half of next week potentially bringing precipitation chances and
  cooling temperatures.

&&

.SHORT TERM /TODAY THROUGH THURSDAY/...
Conditions across the southwestern CONUS remain quiet as
unseasonably strong high pressure continues to sit over the
region. Over the Great Basin, a low-amplitude shortwave is helping
to keep our ridge relatively flat and heights a bit suppressed
compared to yesterday. Nonetheless, 500mb heights remain around
the 90th percentile for this time of year, owing to the amount of
warm air currently over the forecast area. This will translate to
a continuation of surface temperatures running around 10 degrees
above normal for the middle of December. Lower desert highs this
afternoon will range in the middle to upper 70s, with areas in and
around the Imperial Valley getting close to 80 degrees once again.
With little fluctuation in the day-to-day forecast, similar
afternoon highs can be expected for Thursday.

&&

.LONG TERM /FRIDAY THROUGH MID NEXT WEEK/...
After the northern U.S. trough exits into the Plains States on
Thursday, the center of the eastern Pacific ridge will move
closer to our region late Thursday into Friday with H5 heights
peaking over the Desert Southwest between 585-587dm early on
Friday. This peak in heights will help to boost temperatures
starting Friday with the NBM showing highs mostly between 78-81
degrees. The progressive pattern across the northern tier states
will then send another trough across the Pacific
Northwest/Northern Rockies later on Friday into Saturday which
should flatten the ridge slightly and lower heights more into a
582-584dm range on Saturday. This back and forth of slightly
rising and lowering of heights looks to continue through early
next week with Monday showing another temporary bump in heights.
Overall, this will continue to allow for the unseasonably warm
temperatures to last into at least early next week with readings
staying near 15 degrees above normal.

The latter half of next week should bring a pattern change with
models showing decent agreement of a deep Pacific trough setting
up off the West Coast and the ridge gradually moving to the east.
There is still uncertainty with the evolution of the trough and
its strength, but ensembles are quite consistent in showing decent
moisture beginning to spread into our region from the southwest
ahead of the trough by around next Wednesday. Precipitation
chances may become possible at some point later next week, but
confidence remains quite low for the timing. The weather system is
expected to be quite warm, so any precipitation across the area
should fall as rain.

&&

.AVIATION...Updated at 1726Z.

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 the TAF period.
Winds will remain light, aob 8 kts, and diurnal through the TAF
period, with extended variable or calm conditions. Confidence in a
typical westerly switch this afternoon at KPHX remains low,
however, may see a TEMPO westerly component develop for a few
hours late this afternoon into the early evening. Otherwise,
mostly clear skies will prevail for much of the TAF period with
FEW-SCT high clouds continuing into early this afternoon.

&&

.FIRE WEATHER...
Persistent high pressure across the region will result in warm
and dry conditions into early next week. Highs in the upper 70s
to the lower 80s will be common across the lower deserts, or 10 to
15 degrees above daily normals. Winds will overall be light and
follow familiar diurnal patterns. MinRHs will range from 15-25%
while overnight recoveries will generally remain fair up to
40-70%.

&&

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

$$

SHORT TERM...RW
LONG TERM...Kuhlman
AVIATION...Smith
FIRE WEATHER...Kuhlman

NWS Phoenix (PSR) Office