Desert Hot Springs, California Weather Forecast Discussion

373
FXUS66 KSGX 150414
AFDSGX
Area Forecast Discussion
National Weather Service San Diego CA
914 PM PDT Sun Sep 14 2025
.SYNOPSIS...
Gradual warming through mid-week, with gradual cooling for the
second half of the week. An influx of tropical moisture will bring
chances of showers and thunderstorms for the middle to end of the
week. Highest chances of showers and thunderstorms will be in the
mountains and deserts, with lesser chances west of the mountains.
The marine layer will become shallower early in the week, with the
potential for minimal or no low cloud coverage for the middle to end
of the week.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
Evening update...
Marine layer low clouds are spreading into the western valleys
this evening with clear skies elsewhere. The 00Z KNKX sounding
shows the marine inversion has lowered quite a bit under the upper
level ridging today, down to around 1700 ft MSL. Expect far less
inland extent of low clouds tonight with earlier clearing in the
western valleys tomorrow morning. Warming trend will continue
tomorrow as upper level ridging begins to nudge in from the
southeast, with the greatest warming inland. Highs will be near to
a few degrees above normal on Monday, with mid 90s returning for
the Inland Empire and high deserts, low 100s across the low
deserts, 70s to mid 80s in the mountains, mid 80s to mid 90s for
the western valleys, and mid 70s along the coast.
Previous discussion...
The warming trend
will continue for the first half of the week. By Tuesday, the coast
and valleys will be running 5 to 10 degrees above average for this
time of year. The second half of the week is expected to see a
gradual cooling trend. The cooling trend will bring high
temperatures back to below average for most locations by next
Sunday, September 21.
Mid to upper level moisture from Tropical Storm Mario is expected to
become entrained in an upper level area of low pressure off the
coast of Southern California as early as Tuesday. Based on current
guidance, there will be a lack of a strong forcing mechanism on
Tuesday which should result in dry conditions prevailing across the
area although an increase in mid to high clouds can be expected. By
Wednesday, there is expected to be a further increase in moisture
and the environment is expected to become more unstable. Those moist
and unstable conditions are expected to continue into next weekend,
bringing chances for showers and thunderstorms across much of the
area. The highest chances of showers and thunderstorms each day are
in the mountains and deserts (30-60%) but shower/thunderstorms
cannot be ruled out west of the mountains. For areas west of the
mountains guidance is currently showing Thursday and Friday having
the highest chances (20-35%) with lesser chances Wednesday and
Saturday (15-20%). There is still uncertainty surrounding the
details but the majority of ensemble members across model platforms
favor a dry solution for SoCal through Tuesday then a majority favor
a wet solution for Wed through Saturday. Conditions could begin to
dry out next Sunday as we lose access to the moisture from the
south, but for now a chance of showers and thunderstorms remains
in the mountains Sunday afternoon.
&&
.AVIATION...
150300Z...Coast/Valleys...Low clouds based 1000-1500 ft MSL are
quickly developing over coastal areas this evening. Clouds pushing
up to 15 miles inland through 12Z with a 40-50% chance of reaching
into the western and southern Inland Empire (including KONT) late.
VIS 2-5SM is possible overnight for inland valleys and where clouds
intersect with terrain. Clearing to the coastline slightly earlier
Monday around 16-18Z. Patchy clouds again through the afternoon at
the beaches and over waters. Bases continue to lower as clouds
slowly return to coastal land areas after 03Z Tuesday. Vis
restrictions likely over higher coastal terrain Tuesday night.
Mountains/Deserts...Mostly clear and VFR conditions through Monday
evening.
&&
.MARINE...
Tropical moisture will allow for 20-30% chance scattered
thunderstorms over coastal waters Wed-Fri. Any storms that develop
may produce gusty winds and lightning.
&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&
$$
PUBLIC...SS/CO
AVIATION/MARINE...KW

NWS SGX Office Area Forecast Discussion