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Area Forecast Discussion (AFD)

Issued by San Diego, CA (SGX)

                            
000
FXUS66 KSGX 210406
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
906 PM PDT Wed Jun 20 2018

.SYNOPSIS...
High pressure aloft will bring very hot weather to the deserts 
through Friday, followed by slight cooling over the weekend. Coastal 
areas will continue to have low clouds, nights and mornings, with 
only partial afternoon clearing Thursday. It will be mild near the 
coast due to the marine layer. No precipitation is expected through 
at least the middle of next week. Summer will begin Thursday at 3:07 
AM PDT.

&&

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

The marine stratus was extensive and without breaks over the CA 
Bight and surged rapidly inland early this evening in typical June 
fashion with broad coverage of coastal areas. The 00Z Miramar 
sounding had an 11 degree C inversion based near 1800 FT MSL. This 
was about 400 FT lower than yesterday evening. The sfc pressure 
gradient had increased slightly onshore to the NE, but was holding 
to the lower deserts. At 8:30PM PDT...The only wind gust reports 
over 25 MPH were near the desert passes. No forecast changes this 
evening.

From previous discussion...

Stratus along the coast will have widespread coverage to about 20 
miles inland overnight. A strong inversion, possibly 12 deg C or 
more, plus a likely weak eddy will mean that immediate coastal areas 
will have difficult clearing Thursday.

High pressure aloft was building over So-Cal, and will continue 
through Thursday, then slowly slide a bit south Fri/Sat as an upper 
low moves into the interior West. It should be very hot in the 
deserts through Friday. Temperatures could reach around 115 deg F in 
the lower deserts, with Friday looking like the hottest day due to 
the model profiles showing 850 MB temps 29-30 deg C there, with 
local 110 deg F temps in the high deserts either Thu or Fri. The 
excessive heat warning looks good for the deserts for Thu/Fri. 
Models are consistent with showing about 5 deg F cooling Saturday as 
with the weakening of the high and most widespread westerly flow 
aloft. Models are a bit inconsistent early next week, but some 
solutions show a resurgence of the upper high Mon-Wed to bring some 
warming again to the deserts.

&&

.AVIATION... 
210330Z...Coast/Valleys...Low clouds now impacting coastal TAF sites 
with OVC cigs around 1100 ft MSL and tops to 1500 ft MSL. Low clouds 
likely to spread up to 20 miles inland by 15Z Thu. Low clouds and 
reduced vis could reach KONT later tonight but timing is uncertain. 
Reduced VIS 1-3SM will be possible near elevated terrain. Expect 
clearing to the coast between 18Z and 21Z Thu, although SCT-BKN 
clouds around 1500 ft MSL could linger at KSAN and KCRQ into the 
afternoon.  

Mountains/Deserts...Mostly clear with unrestricted VIS through 
Thursday. 

&&

.MARINE...
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 from 11 AM Thursday to 8 PM PDT Friday 
     for Apple and Lucerne Valleys-Coachella Valley-San Diego 
     County Deserts-San Gorgonio Pass Near Banning.

PZ...NONE.

&&

$$

PUBLIC...10/Maxwell
AVIATION/MARINE...PG