Area Forecast Discussion
Issued by NWS San Diego, CA

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393
FXUS66 KSGX 221052
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
352 AM PDT Thu Jun 22 2017

...Excessive heat to continue through Monday in the lower deserts
including the Coachella Valley...

.SYNOPSIS...
Continued hot in the deserts through Monday under high pressure
aloft. It will not be quite as hot in the valleys the next couple
of days as onshore flow increases, extending the marine influence
farther inland. The marine layer will continue to moderate
temperatures in the coastal region with clouds lingering into the
afternoons at some of the beaches. The mountains will remain
hot through the weekend.

&&

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

Excessively hot conditions will continue across the deserts
through Monday as a high pres ridge remains entrenched across the
SW region. The build up over many days means a continued threat to
public safety even as the temperatures have fallen a few degrees
below the hottest temperatures of a couple days ago.

Although temperatures will not be quite as hot as what we saw a
few days ago, a minor flare up in the temperatures will occur
Sunday as the high becomes a tad stronger and temperatures may
flirt with the 120 mark once again in the lower deserts. The
excessive heat warnings have been extended for the lower deserts
through Monday as temperatures will reach excessive levels once
again.

A strong and shallow marine layer will continue cloudy and foggy
conditions near the coast and into the western valleys each night
and morning. As the high strengthens this weekend the marine
intrusion will probably focus back right along the coastal strip.
Then after Monday should deepen again and bring more extensive
cooling into the valleys.

The ridge breaks down after Monday as the high slowly flattens
out and by mid next week a Pacific trough slowly builds into the
west coast...bringing an increase in cooling temps aloft to all of
the region and finally inland temperatures should settle back a
little closer to near normal levels.

&&

.AVIATION...
220930...Coast/Valleys...Areas of low clouds and fog have spread as
much as 15 miles inland at this hour and could spread even farther
inland by 14Z. Bases are around 400 feet msl with tops to 1100 feet.
Vis 3-5sm near sea level, but locally 1SM or less especially on
coastal mesas. Expect clearing to the beaches 16-17Z, but patches of
low clouds will linger at the beaches into the afternoon. Low clouds
and fog likely to begin moving inland again after 03Z Fri.

Mountains/Deserts...Clear skies with unrestricted vis through today.
Estimated density altitude of about 4000 ft at KPSP and KTRM with
max temperatures 115-118 this afternoon.

&&

.MARINE...
A shallow marine layer will continue to bring patchy dense fog (with
visibilities of 1 NM or less) to the coastal waters this morning.
Dense fog will be possible during the nights and mornings through
the weekend. Otherwise, no hazardous marine weather is expected
through Sunday.


&&

.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.

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

PZ...NONE.
&&

$$

PUBLIC...Brotherton
AVIATION/MARINE...PG



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