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Area Forecast Discussion (AFD)

Issued by San Diego, CA (SGX)

FXUS66 KSGX 201557

Area Forecast Discussion
National Weather Service San Diego CA
900 AM PDT Wed Jun 20 2018

High pressure aloft will bring very hot weather to the deserts 
through Friday with slight cooling over the weekend. Coastal areas 
will continue to have low clouds, especially during the nights and 
mornings, though only partial afternoon clearing will occur on some 
days. 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.



Stratus was widespread this morning to about 20-25 miles inland from 
the coast. Clearing had only begun as of 830 AM at the most inland 
extent of the clouds. Clearing should occur mostly by 10 AM 10-20 
miles inland, but the 11 deg C inversion will make it difficult for 
the clouds to clear near the coast this afternoon. Above the 
inversion, temps have increased substantially in the past 24 hours, 
with the 12Z NKX sounding showing 900 mb temps 10 deg C higher than 
Tuesday, and an 850 mb temp of 23-24 deg C. Thus, it will be hot in 
the deserts today, with some areas topping 110 in the lower deserts.

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 still 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.


201530Z...Coast/Valleys...OVC014 tops 2100 ft MSL extending 20 miles 
inland this morning will retreat back to the coast through 22Z. 
Skies may not completely clear from KSAN, KCRQ and KSNA, with the 
best chance for clearing between from 22-01Z. 

Stratus spreading back inland after 01Z this evening with cloud 
bases lowering to OVC010-013 tops 2000 ft MSL by 12Z Thursday. 

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


No hazardous marine weather through Sunday.


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


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.