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318
FXUS66 KSGX 070409
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
909 PM PDT Thu Jun 6 2024

.SYNOPSIS...
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Night and morning low clouds and fog are expected each day. A
shallow marine layer tonight into Friday, will slowly deepen into
next week, allowing low clouds and fog to spread further into the
valleys. A few degrees of cooling is expected for inland areas on
Friday, but highs will mostly remain above average. Further cooling
is expected this weekend. Conditions will gradually warm early next
week.
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&&

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

At 9 PM, low clouds were filling in along the coast with clear skies
elsewhere. Low cloud coverage is expected to make it into portions
of the western valleys tonight into Friday morning. Highs on Friday
will be a few degrees cooler than Thursday inland as the ridge axis
that was over the Western US weakens and moves eastward. Additional
cooling is expected Saturday and Sunday. The weakening high pressure
aloft will also allow the marine layer to deepen this weekend,
reaching further into the Inland Empire.

From Previous Discussion...

For Saturday, highs will top out near 70 at the coast, the mid-70s
to mid-80s in the valleys, the upper-70s in the mountains, the mid-
90s in the High Desert and the mid-100s in the lower deserts.
Highs fall a few more degrees on Sunday.

Ensemble guidance begins to diverge early next week. A closed low
looks to break off from the mean flow Sunday or Monday and slowly
meanders to the southwest before parking off the coast of Southern
California or Baja California. The most noticeable impact from this
will be increasing high clouds region-wide Sunday through the middle
of next week. The low-levels look moisture starved so no
precipitation is expected.

To the north, a building ridge will lead to slow warming again on
Monday and Tuesday. The major questions with the forecast are where
the low ends up and how strong it is, and when and where the upper
low is going to become absorbed into the mean flow.
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&&

.AVIATION...
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070400Z...Coast/Valleys...Low clouds with bases 600-1200 ft MSL and
tops to 1800 ft MSL will continue to spread 10-20 miles inland by
05Z and up to 40 miles inland by 12Z Fri. Latest indications are
that KONT will have a CIG and reduced VIS 1-3 miles by 10Z Fri.
Higher terrain will be obscured, with areas of VIS 1-3 miles below
the cloud bases 06Z-17Z Fri. Clearing will occur 14Z-17Z Fri over
the valleys and partially clear 17Z-22Z Fri near the coast with
areas of BKN/OVC clouds lingering within 3 miles of the coast
through Fri afternoon. Low clouds will spread inland again Fri
evening with slightly higher bases/tops.

Mountains/Deserts...Clear skies and unrestricted VIS will continue
through Fri evening.
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&&

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

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 9 PM PDT Friday for San Bernardino and
     Riverside County Valleys-The Inland Empire.

     Excessive Heat Warning until 9 PM PDT Friday for Apple and
     Lucerne Valleys-Coachella Valley-San Diego County Deserts-
     San Gorgonio Pass Near Banning.

PZ...None.

&&

$$

PUBLIC...CO
AVIATION/MARINE...Maxwell