Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 181012
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
312 AM PDT Sun Jun 18 2017

.SYNOPSIS...
High pressure aloft over the southwest states will bring well
above average high temperatures through mid week...peaking
Tuesday and Wednesday. A shallow marine layer and weak onshore
flow will moderate the heat towards the coast with areas of night
and morning coastal low clouds and locally dense fog becoming
patchier Tuesday and Wednesday. High pressure may weaken slightly
the latter part the next week with cooling spreading into the
valleys Thursday...with slight cooling spreading farther inland on
Friday and Saturday.

&&

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

High pressure aloft over the southwest states will continue to
strengthen the next few days...reaching peak intensity on Tuesday
while centered over Arizona. High pressure will slowly weaken for
Wednesday and Thursday as a weak trough of low pressure develops
over central California. High pressure is expected to then
strengthen a little into next weekend with the center a little
farther to the southeast than earlier this week...somewhere near
southeastern Arizona into adjacent parts of northern Mexico.

High temperatures are expected to warm slightly today for inland
areas...with steady slow warming for Monday through Wednesday.
This will push high temperatures to 12 to 18 degrees above average
for inland areas on Wednesday...and to around 5 degrees above
average near the coast with Wednesday high temperatures around 120
in the lower deserts...around 112 in the upper deserts...and 102
to 112 in the Inland Empire. Cooling is expected to begin
spreading inland on Thursday with less cooling for Friday and
Saturday.

Towards the coast...the marine layer is slightly shallower than 24
hours...around 1000 feet deep...with satellite imagery showing
widespread stratus over the coastal waters extending locally
inland. Fog could be locally dense early this morning near the
mesas and other higher coastal terrain. The marine layer may
become a little shallower for tonight into Monday morning...with
patchier stratus coverage for Tuesday and Wednesday. As high
pressure aloft weakens later in the week...overnight stratus
coverage is expected to increase in coverage with night and
morning coastal low clouds and fog extending locally inland at
times...but not much farther than the far western valleys.

Small amounts of mid level moisture may flow into far Southern
California from the southeast at times from Wednesday into next
weekend with a few mid clouds at times and a few afternoon clouds
over the mountains at time.

&&

.AVIATION...
180930Z...Coast...Areas of low clouds are now spreading slowly
inland and could extend locally 5-10 miles inland by 12Z. Bases are
between 900 and 1100 ft MSL, with visibility around 6 miles. Local
visibility reductions of 1 SM or less may occur over the coastal
mesas. KSAN, KCRQ, and KSNA should all be affected, with a low
probability of visibility below 5 miles at KCRQ til 14Z. Rapid
clearing is expected after 15Z. Low clouds and fog may return to the
coastal areas after 03Z Monday. Elsewhere, clear skies with
unrestricted visibility will prevail through today.

&&

.MARINE...
Patches of fog with visibility 1 mile or less will occur over the
coastal waters through Thursday, mainly during the early morning
hours. Otherwise, no hazardous marine weather is expected through
Thursday.

&&

.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 Riverside County
     Mountains-San Bernardino County Mountains-San Bernardino
     and Riverside County Valleys-The Inland Empire-San Diego
     County Mountains.

     Heat Advisory from 11 AM Monday to 9 PM PDT Wednesday for Orange
     County Inland Areas-San Diego County Valleys-Santa Ana
     Mountains and Foothills.

PZ...NONE.

&&

$$

PUBLIC...17
AVIATION/MARINE...PG



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