Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 241120
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
420 AM PDT Sat Jun 24 2017

.SYNOPSIS...
High pressure aloft centered over southern Arizona and northwest
Mexico will continue the very hot weather through the weekend for
inland areas with the marine layer keeping coastal areas cooler
with areas of night and morning low clouds and fog lingering near
some beaches each afternoon. Mid level moisture and clouds moving
northwestward across the area this morning will decrease during
the afternoon. High pressure aloft will weaken and move to the
south next week as a pair of low pressure systems moves inland to
the north through Wednesday. This will bring cooling for inland
areas with high temperatures near average for Wednesday into next
weekend. The marine layer will deepen with cooling and areas of
night and morning coastal low clouds and fog extending into
portions of the inland valleys for the latter half of next week.

&&

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

.SHORT TERM (Today through Monday)...
High pressure aloft centered over southern Arizona and northwest
Mexico will bring slow warming for inland areas into Sunday. High
temperatures for inland areas are expected to peak on Sunday...
around 3 to 5 degrees cooler than the peak of the heat this past
Tuesday and Wednesday. This will still push hottest high
temperatures in the lower deserts to around 118...near 112 in the
upper deserts...and near 106 in the corridor from Lake Elsinore to
Hemet in the Inland Empire. High pressure aloft is expected to
begin weakening on Monday with a few degrees of cooling for inland
areas.

Water vapor imagery shows a cyclonic circulation early this
morning over the eastern Pacific...somewhat to the west of Point
Conception. This is drawing mid level moisture toward the
northwest...mostly across the coastal waters of Southern
California into adjacent portions of Southern California. This
moisture is quite elevated...mostly centered around 500 mb. There
is also some weak elevated instability off the coast...mostly
centered near and to the west of the offshore islands. There have
been a few lightning strikes overnight with this band of
moisture...mostly around 60 miles off the coast of northern Baja.
The mid level moisture and clouds should gradually decrease from
south to north during the afternoon.

The marine layer remains near 1500 feet deep early this morning
with widespread stratus over the coastal waters extending into
inland orange County and the far western valleys in San Diego
County. The marine layer may become a little shallower the next
two nights with the stratus not extending quite as far inland.
Afternoon clearing may continue to be slow or limited at
times at the beaches...mainly for portions of the San Diego
County coast.

&&

.LONG TERM (Tuesday through Friday)...
Slow cooling will continue for Tuesday and Wednesday followed by
minor day to day fluctuations into next weekend with high
temperatures for inland areas returning to near average for
Wednesday into next weekend. The local workstation WRF nest of the
GFS shows a weak eddy at times for Wednesday through Friday. This
is expected to bring slow deepening of the marine layer with night
and morning coastal low clouds and fog extending into portions of
the inland valleys.

&&

.AVIATION...
240940Z...Coast/Valleys...Areas of stratus with bases 800-1200 ft
MSL continuing over the coastal basin this morning. CIGS unlikely to
reach KONT. Stratus clearing to the coast 16-19Z, though some
beaches may remain BKN-OVC through the afternoon. Stratus returning
to the coastal airports after 02Z and spreading into the far western
valleys overnight. Bases remaining around 800-1200 ft MSL. Otherwise
SCT-BKN clouds AOA 15000 ft MSL and unrestricted vis through Sunday
morning.

Mountains/Deserts...SCT-BKN clouds AOA 15000 ft MSL and unrestricted
vis through Sunday morning.

&&

.MARINE...
A weak wave with with instability aloft will lift north off the
coast of So Cal this morning, bringing a slight chance of
thunderstorms to the outer coastal waters through late morning.
Cloud-to-water lightning will be the main hazard. Little
precipitation is expected with these storms. The thunderstorm threat
will diminish this afternoon.

Northwest wind gusts over the outer waters may reach 20-25 kt during
the afternoons and evenings Sunday through Tuesday, potentially
resulting in conditions hazardous to small craft.

&&

.BEACHES...
High tides will reach 7+ ft again this evening. Tides this high may
result in minor tidal overflow at low lying beaches. The Beach
Hazards Statement continues through 11 PM this evening. High tide
will fall below 7 feet Sunday, lowering the tidal overflow threat.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...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-Santa Ana Mountains and Foothills.

     Excessive Heat Warning until 9 PM PDT Sunday for Apple and
     Lucerne Valleys.

     Beach Hazards Statement through this evening for Orange County
     Coastal Areas-San Diego County Coastal Areas.

PZ...NONE.

&&

$$

PUBLIC...17
AVIATION/MARINE/BEACHES...SS



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