704
FXUS66 KSGX 070117
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
617 PM PDT Thu Aug 6 2026

.SYNOPSIS...
Through Sunday moderate HeatRisk expected in the mountains and
Inland Empire with major to extreme HeatRisk in the deserts. There
are chances 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...


...UPDATED AVIATION DISCUSSION...

Visible satellite at 11 AM was showing areas of high clouds across
the area with low clouds off the coast. There remain chances of
isolated showers and thunderstorms in the mountains this afternoon.
Latest REFS guidance indicates a decrease in the 90th percentile
maximum hourly rainfall rate this afternoon, down to 0.45 inches per
hour. There is only a 10 percent chance of hourly rainfall rates
exceeding that. Guidance continues to indicate 15-20 percent
chance of isolated showers and thunderstorms over area mountains
through Saturday, with guidance indicating hourly rainfall rates
will be less than 0.50 inch per hour.

Through Sunday high temperatures are expected to run 5 to 10 degrees
above average for 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,
mountains, and portions of inland Orange County and San Diego
valleys 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
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). High temperatures are expected to gradually decrease next
week, bringing temperatures back down to near or slightly below
average by the middle of next week.

For Sunday and Monday, precipitable water values are expected to
peak which will result in more widespread shower and thunderstorm
chances across the mountains. Shower chances will become more
isolated again Tuesday and Wednesday.

&&

.AVIATION...

070100Z....Coasts...Patchy low clouds to gradually increase
overnight, but confidence is low that cigs will be prevalent and
uniform. Cigs of 900-1200 feet MSL are most likely between 10-16Z
Friday. Low clouds with similar bases to redevelop after 05Z
Friday night. Otherwise, SCT clouds above 10000 feet MSL through
20Z Friday.

.Valleys/Mountains/Deserts...SCT to locally BKN clouds AOA 10000
feet MSL through Friday afternoon.

&&

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

&&

.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 Sunday 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 Sunday for Apple and Lucerne
     Valleys-Coachella Valley-San Diego County Deserts-San
     Gorgonio Pass near Banning.

PZ...None.

&&

$$

PUBLIC...CO
AVIATION/MARINE...MM