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Area Forecast Discussion (AFD)

Issued by San Diego, CA (SGX)

FXUS66 KSGX 202107

Area Forecast Discussion
National Weather Service San Diego CA
200 PM 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 
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.



Skies were sunny except for areas of lingering stratus along the 
immediate coast at early afternoon. Due to substantial warming 
aloft, the inland valleys, mountains and high deserts were 5-10 deg 
F warmer than 24 hours ago, with Campo somewhat oddly is 18 deg F 
warmer with a 1 PM temperature of 98 along with some offshore flow, 
(they've since cooled to 93 at 2 PM). Some northeast flow was 
evident in the NKX and aviation soundings this morning, reaching the 
surface in some mountain areas (33 MPH peak gust at Volcan 
Mountain), though this will weaken later today, with much less 
northeast flow Thursday. 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 

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.


202030Z...Coast/Valleys...BKN015 tops 2100 ft MSL near the coast 
becoming OVC010-015 and spreading 20 miles inland through 15Z 
Thursday. Skies will clear back to the coast through 21Z Thursday 
with SCT-BKN015 at KSAN and KCRQ from 21Z-02Z.  

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.