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630
FXUS66 KSGX 060428
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
928 PM PDT Wed Jun 5 2024

.SYNOPSIS...
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Hot conditions will continue for inland locations through Friday.
Thursday will be the peak of the heat, with a few degrees of cooling
expected for Friday. A gradual cooling will continue through Sunday.
Regardless of the cooling trend, highs in the deserts will remain
about 5 degrees above average through the weekend. The marine
layer will remain shallow through Friday mainly impacting the
coast and portions of the western valleys, slowly deepening into
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...

As of 9 PM tonight, low clouds have filled in along the San Diego
and Orange County coasts and have reached into the western valleys.
The inversion on the 00Z sounding at KNKX was 400 ft lower than
yesterday`s 00Z sounding. Forecast is still on track, with hot
conditions continuing for inland locations for Thursday and Friday.
Thursday will be the peak of the heat for the low deserts, with a
few degrees of cooling expected for areas west of the mountains. For
Friday two low pressure systems, off the coast of Baja and moving
southwest off the Gulf of Alaska, will push the ridge further east
leading to a few degrees of cooling. Even with a few degrees of
cooling, temperatures will still remain above average for inland
locations with moderate to areas of major heat risk in the deserts.

From Previous Discussion...

Highs Thursday and Friday will generally be anywhere from 8 to 15
degrees warmer than seasonal averages. In other words, these highs
are more representative of what wed expect in late July/early
August. With that in mind, most of this heat looks to be non-record-
setting in terms of daily high temperatures. On the flip side, a few
daily records for warmest overnight low temperatures do look to be
challenged, mainly in some mountain communities. More notable
cooling sets in for all areas Saturday.

With the warming trend, the marine layer looks to remain fairly
shallow through at least Friday. The low-level inversion is expected
to strengthen which will likely keep clouds at the immediate coast
through the afternoon hours each day. The return of troughing over
the Eastern Pacific and the subsequent cooling trend this weekend
into early next week will lead to a re-deepening of the marine
layer, with low clouds getting back into more of the inland valleys
later this weekend.

The aforementioned trough and cooling trend will knock daily highs
back down to around seasonal averages across areas west of the
mountains. The mountains and deserts, however, will still see highs
remain slightly above normal. The pattern then becomes a bit more
murky heading into next week as a closed 500mb low looks to form
off the SoCal coast underneath a broad ridge. These two competing
features make discerning trends in temperatures/sensible weather a
bit more difficult, as temperatures may only fluctuate up or down
a degree or two each day depending on marine layer depth and
associated cloud cover. Its worth nothing that we will be
starting next week with a relatively deep marine layer, generally
on the order of 2000-2500 FT MSL deep. So if the overall upper
level pattern doesnt support a very dynamic forecast, cool and
cloudy may be the prevailing theme of next week, typical for June
Gloom.
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&&

.AVIATION...
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060400Z...Coast/Valleys...OVC005-010 tops 015 spreading 15-20 miles
inland through 18Z Thu with areas vis 3-5SM in BR/HZ. Clouds
clearing back to the coast through 22Z but with only brief coastal
clearing at KSAN, KCRQ and KSNA 22Z-24Z. Low clouds surging back
inland 00-06Z Fri.

Mountains/Deserts...Mostly clear with unrestricted VIS through
Thursday.
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&&

.MARINE...
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No hazardous marine conditions are expected through Saturday.
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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/Adams
AVIATION/MARINE...Moede