398
FXUS66 KSGX 051905
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
1205 PM PDT Wed Aug 5 2026

.SYNOPSIS...
Increased HeatRisk expected through Saturday with moderate HeatRisk
for the mountains and Inland Empire with major to extreme HeatRisk
in the deserts. There is a chance of showers and isolated
thunderstorms in the mountains each afternoon through Tuesday.
Coastal areas will continue to see low clouds each night and morning
through the forecast period.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

Visible satellite at 11 AM was showing marine layer low clouds
slowly clearing from the coast. The inversion on the 12Z KNKX
sounding was about 10 degrees so clearing at the beaches this
afternoon may be patchy. Low clouds will remain constant at the
coast each night and morning through the forecast period, reaching
into portions of the western valleys at times.

Thursday through Saturday highs will be above average near the coast
to 5 to locally 10 degrees above average for some inland areas. Low
temperatures will also run above average, most noticeable in the
mountains and deserts where lows will be 10 to 15 degrees above
average. For the Inland Empire and mountains, widespread moderate
HeatRisk is expected which means that folks who are sensitive heat,
especially those without consistent cooling/hydration will be most
impacted. In the deserts, major to locally extreme HeatRisk
indicates anyone may see negative impacts from the heat if
precautions aren`t taken. Make sure to stay hydrated and if possible
avoid strenuous activity during the hottest parts of the day (10 AM
to 4 PM).

The flow aloft will turn southeasterly Thursday and remain
southeasterly into early next week. This would allow for some
monsoonal moisture into the area and bring a 15 to 20 percent chance
of showers and isolated thunderstorms to the mountains each
afternoon. Through Friday, there is only a 15 percent chance of
rainfall rates exceeding 0.50" per hour in any showers that develop
in the mountains. Current forecast follows the NBM which has chances
each afternoon, with most widespread coverage Sunday and Monday.

&&

.AVIATION...
051800Z....Coasts/Valleys...Satellite shows low clouds are quickly
eroding back towards the coast, with clearing expected for coastal
TAF sites by 19z. Patchy stratus may linger at the beaches through
the afternoon. Low clouds redevelop and move inland again this
evening, likely after 03z Thur, with slightly lower bases around
1000-1500ft MSL. VIS down to 3-5SM for inland valleys and coastal
terrain. Clearing on Thursday will occur a little earlier, likely by
16-18z.

.Mountains/Deserts...SCT-BKN clouds AOA 20,000ft MSL with
unrestricted VIS through Thursday.

&&

.MARINE...
No hazardous marine conditions are expected through Saturday.

&&

.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 8 PM PDT Saturday for Riverside County
     Mountains-San Bernardino County Mountains-San Bernardino
     and Riverside County Valleys-The Inland Empire-San Diego
     County Mountains.

     Extreme Heat Warning until 8 PM PDT Saturday for Apple and
     Lucerne Valleys-Coachella Valley-San Diego County Deserts-
     San Gorgonio Pass near Banning.

PZ...None.

&&

$$

PUBLIC...CO
AVIATION/MARINE...Zuber

NWS San Diego (SGX) Office