Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 200955
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
255 AM PDT Tue Jun 20 2017

.SYNOPSIS...
Daytime high temperatures will continue to increase through
Wednesday. A shallow marine layer will continue to moderate
conditions along the coast with areas of nocturnal clouds and
fog...lingering into the afternoons at some beaches. It will be a
little cooler to end the week as onshore flow increases, extending
the marine influence farther inland. Inland areas will remain
seasonably warm. Summer officially begins at 9:24 PM on Tuesday.

&&

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

This morning...Marine layer low clouds are widespread over the
coastal waters and extend up to 5 miles inland in some places. As
the low clouds spread inland, patches of dense fog are likely over
higher coastal terrain. The clouds and fog will clear to the
beaches by about 9 am but some low clouds could linger at the
beaches into the afternoon. Yesterday`s high temps reached the
upper 90s in the high deserts, into triple digits across portions
of the inland valleys and as high as 119 degrees F at Palm
Springs.

The high pressure ridge responsible for the hot weather is
expected to dominate the pattern for the foreseeable future with
only minor adjustments at times. Temperatures are expected to
increase for today and Wednesday as the upper high now centered
over AZ expands westward and heights rise over SoCal. Onshore flow
and the shallow marine layer will continue to moderate temps near
the coast, with nocturnal low clouds and fog.

Temperatures lower by a few degrees on Thu and Fri (even inland)
as the high weakens slightly and heights fall over SoCal.

Thus far, any monsoonal moisture has remained well to our east and
north, but at least one numerical model is indicating that some of
that moisture could make its way into SoCal on Sat and Sun. At
this time, this scenario is still speculative but it could have
interesting consequences should it materialize.

&&

.AVIATION...
200919Z...Coast...Low stratus/dense fog likely within 5-10 sm inland
(and locally 15 sm inland) through 1500 UTC, with bases 200-600 ft
msl, tops around 800-1000 ft msl, areas of vis 1-5 sm and local vis
1/4 sm or less. KCRQ likely to have dense fog, while KSAN and KSNA
likely to at least have vis down to 1 sm, if not lower. Clearing
taking place during the 1500-1700 UTC time-frame. 1700-21/0300 UTC,
primarily P6SM vis and SKC except for a few patches of low clouds
400-1000 ft msl possibly lingering near and along the beaches.
21/0300-1500 UTC, low stratus/dense fog likely re-developing in the
same locations with similar vis/cigs/tops as this morning.

Valleys/Mountains/Deserts...P6SM vis and SKC through Wednesday
morning. High density altitude at KPSP and KTRM with max
temperatures 118-122 deg F.

&&

.MARINE...
Areas of dense fog producing visibilities of 1 nm or less remain
possible through Thursday during the nights and mornings. Otherwise,
no hazardous marine weather is anticipated through Saturday, with
mixed seas of 4 ft or less and weak-moderate northwest winds.

&&

.BEACHES...
A southerly swell from 165-170 degrees, in addition to short-period
westerly swells and large tidal swings (high tides of 6.5-7 ft with
low tides around -1.0 ft), will result in strong and dangerous rip
and longshore currents through Thursday. This swell will also likely
bring some 5 foot surf to Orange county beaches and San Diego county
beaches north of Oceanside. A Beach Hazards Statement remains in
effect through 10 PM Thursday. This Statement may need to be
extended beyond Thursday for possible minor tidal overflow due to
the aforementioned high tides which peak Friday evening at around
7.3 feet (when the residual between predicted and observed tides is
factored in).

&&

.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 Thursday for Apple and
     Lucerne Valleys-Coachella Valley-San Diego County Deserts-
     San Gorgonio Pass Near Banning.

     Heat Advisory until 9 PM PDT Wednesday for Orange County Inland
     Areas-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.

PZ...NONE.

&&

$$

PUBLIC...PG
AVIATION/MARINE/BEACHES...Harrison



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