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Area forecast discussion
National Weather Service San Diego California
900 am PDT Thu Jun 21 2018

Synopsis...
high pressure aloft will bring hot weather to the deserts today
through Friday, but onshore flow and a strong marine layer will
continue the mild weather along the coast with extensive night and
morning low clouds, and only partial afternoon clearing. The high
pressure system will weaken over the weekend and bring cooler
weather to inland areas. Fair weather will continue early next week
with temperatures increasing slightly, but night and morning low
clouds will continue near the coast.

&&

Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
counties...

Stratus was widespread in most areas west of the mountains early
this morning, including quite a few parts of the inland Empire.
There was even a little bit of drizzle around San Diego int'l
Airport and North Island. Nkx sounding this morning had the marine
inversion base at 1300 ft mean sea level but with an inversion strength of 14
deg c. This will combine with the weak eddy to result in very slow
clearing along the coast, with many beaches likely staying cloudy
this afternoon. Inland areas were already starting to clear, and
sunny skies will prevail by 10-11 am everywhere east of about 5
miles from the coast. Of course, the deserts will be hot today,
though slightly hotter Friday.

High pressure aloft is centered over northwest Sonora, and a roughly east-
West Ridge of high pressure will continue today and then shift a
little bit south farther into Mexico Friday and Saturday as
troughing developing to the north. While heights fall slightly
Friday, 850 mb temps peak then, so most of the deserts, especially
the lower deserts, will have their hottest day Friday. The lower
deserts should be mostly around 110 or slightly higher today and 112-
115 Friday. The high deserts will be 102-108. An upper low moving
through Idaho/northern Nevada/northern Utah Saturday will bring weak
cyclonic flow aloft here, versus the previous anti-cyclonic flow and
also force the high to be farther south and also farther west over
the ocean. It will end up being 5-8 deg f cooler over inland areas
Saturday, with little change Sunday. While clouds will likely linger
along the coast today/Friday, the cooling aloft should result in
better afternoon clearing over the weekend. Some warming could
return early next week as the high aloft gradually expands,
extending all the way from the central Pacific to Texas. Monsoonal
moisture should stay well to the southeast, so no precipitation is
expected through late next week except for very minor drizzle from
the marine layer at times.

&&

Aviation...
211545z...coast/valleys...marine layer a little deeper and cloud
layer a little thicker this morning with ovc008-012 tops 2200 ft mean sea level
extending all the way to kont and kral early this morning where vis
was 3-5 miles in fg/hz. The low clouds will clear from inland areas
by late morning, but will likely linger along the immediate coast
throughout the day. Clearing at the coastal airports (ksan, kcrq,
ksna) will be limited to between 21-24z.

Tonight: low stratus with broken-ovc008-012 tops 2000 ft spreading back
inland into the valleys again through 14z Friday.

Mountains/deserts...mostly clear with unrestricted visible through
Friday morning.

&&

Marine...
no hazardous marine weather is expected through Monday.

&&

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

&&

Sgx watches/warnings/advisories...
California...excessive heat warning from 11 am this morning to 8 PM PDT
Friday for apple and Lucerne valleys-Coachella Valley-San
Diego County deserts-San Gorgonio Pass near Banning.

Pz...none.

&&

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