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Area forecast discussion
National Weather Service San Diego California
908 PM PDT Thu Jun 22 2017

Synopsis...
strong high pressure will continue to bring hot weather to the
Southern California interior while the marine layer will dominate
near the coast. There is a slight warming trend and less
extensive coastal cloudiness for the weekend. A gradual cooling
trend will develop next week.

&&

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

It was another hot day inland, but not as hot as the last couple
days. The deserts experienced another shallow Gulf surge like
yesterday, which brought in slightly more humid air to disallow
the temps to skyrocket. Palm Springs and 29 Palms topped the heat
list with 113 degrees. Meanwhile, back at the coast the marine
layer flexed its muscles. Some beaches cleared this afternoon
while others didn't. It was also a deeper marine layer which
allowed some coastal clouds into western valleys early this
morning, and even into the south and West Corners of the inland
Empire. That more extensive version of the marine layer really
tamped down the inland valley heat with Max temps coming up 8-12
degrees short of those yesterday. The high pressure ridge aloft
loosened its grip just enough for these influences to make things
a little cooler. A weak shortwave from the south will draw up some
moisture now seen in central Baja California into Alta California
Friday into Saturday. We saw hints of this moisture this
afternoon with a few high clouds over the Lower Desert and a few
cumulus clouds near the big bear area. We'll see more of both
these cumulus over mountains and random altocumulus clouds Friday
and Saturday. There is some weak instability floating overhead
too, but that weak unstable layer is so high up that we feel there
is no chance of showers or thunderstorms. The high pressure ridge
over Arizona will expand slightly over the weekend and that will
bring back the drier heat with temps that could rival those from
earlier this week. Sunday looks like the hottest day. Accordingly,
a heat warning over the deserts through Sunday and a heat
advisory for the valleys (sunday only) are in effect. The marine
layer will get squashed once again and coastal clouds will get
shoved back to the coast. Next week the ridge breaks down slightly
into a westerly zonal pattern that promises a rather seasonal
finish for June.

&&

Aviation...
230400z...coast/valleys...bkn/ovc stratus will continue to spread
inland this evening and cover most south and west parts of the
inland Empire by 08z, including kont. Bases will be slightly higher
than Wed night, mostly 700-1200 ft mean sea level with tops to 1800 ft mean sea level.
Areas of vis below 3 miles in fog will occur in the valleys, with
areas of terrain obscured in clouds. Clearing will be slow Friday,
16z-18z in the valleys and mostly 18z-21z along the coast with some
beach locations with broken/overcast conditions Fri afternoon. Stratus will
spread inland again Friday evening.

Mountains/deserts...mostly clear skies with unrestricted vis will
prevail through Friday evening.

&&

Marine...
patchy dense fog is unlikely tonight but could occur over the
coastal waters at times over the weekend.

Northwest wind gusts over the outer waters may reach 25 kt during
the afternoons and evenings from Sunday through Tuesday, potentially
resulting in conditions hazardous to small craft.

&&

Beaches...
a south swell of 3-4 ft at 13-15 seconds from 165-170 degrees
combined with a short-period west swell and large tidal swings will
result in strong and dangerous rip and longshore currents through
Friday. This swell will also produce surf to 3-6 ft (with local sets
to 7 ft) at Orange County beaches and San Diego County beaches north
of Oceanside. Also, the high tides will likely reach around 7+ ft
during the evenings through Saturday. Tides this high may result in
minor tidal overflow at low lying beaches. The beach hazards
statement continues through late Saturday evening. The high tides
will fall below 7 feet Sunday, lowering the tidal overflow threat.

&&

Fire weather...
brisk winds will continue each afternoon and evening from the
mountain peaks, down the desert slopes and into portions of the
deserts. The hot weather and low humidity will make for critical
fire weather conditions for a few hours during these times through
the weekend. Some upper level moisture and weak instability will
move into the area Friday and Saturday, but appears too limited to
produce any thunderstorms with dry lightning.

&&

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

&&

Sgx watches/warnings/advisories...
California...excessive heat warning until 9 PM PDT Monday for Coachella
Valley-San Diego County deserts-San Gorgonio Pass near
Banning.

Heat advisory from 10 am to 9 PM PDT Sunday for Riverside County
mountains-San Bernardino County mountains-San Bernardino
and Riverside County valleys-the inland Empire-San Diego
County mountains-San Diego County valleys-Santa Ana
Mountains and foothills.

Excessive heat warning until 9 PM PDT Sunday for apple and
Lucerne valleys.

Pz...none.

&&

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