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Area Forecast Discussion (AFD)

Issued by San Diego, CA (SGX)

FXUS66 KSGX 182029

Area Forecast Discussion
National Weather Service San Diego CA
129 PM PDT Sat Aug 18 2018

High pressure will strengthen over the area through tonight, 
continuing to dry and stabilize the atmosphere. Onshore flow and a 
shallow marine layer will continue areas of night and morning low 
clouds over coastal and western valley areas into the upcoming week. 
Daytime temperatures will be near, to a bit above average, while 
overnight lows continue between 5 and 10 degrees higher then average 
due to the elevated sea surface temperatures. Monsoonal moisture may 
return by the middle of next week, rekindling the chance for 
mountain and desert thunderstorms. 



Satellite imagery at midday showed marine stratus hanging onto 
coastal San Diego County and still over a good chunk of the inner 
waters. Farther to the east...patchy cumulus clouds were bubbling 
over the mts. Except for the desert passes where westerly winds were 
occasionally gusting 25-30 MPH, winds were mostly light.

Latest available Hires WRFEMS and HRRR runs are showing a couple of 
showers popping over the mts this afternoon, so the small chance 
will remain in the forecast. Otherwise, look for dry weather with 
moderate to high humidity and little temp change through Monday. 

Strengthening high pressure aloft over SoCal through tonight will 
begin to shift back to the SE through Tue as a trough deepens over 
the PacNW. The net result will be a slight warming early next week, 
and then a possible return of some monsoonal moisture by midweek. 
The chance of thunder returns to the mts by Tue afternoon as a 
result of the shift back to SE flow aloft.

Looking at the 12Z ECMWF/GFS runs...both handle the overall pattern 
similarly, and both suggest less mid-level moisture will return to 
the area than this past week. However, enough is there to leave the 
forecast as is. Other features of note...Both models trend 500H 
lower and show increasing SW flow aloft into next weekend. This 
should result in gradual cooling and decreasing thunder chances 
over the mts. 

182030Z...Coasts/Valleys...Low clouds will redevelop and spread 
inland after 01Z with bases 1000-1400 feet MSL and spread not as far 
inland overnight. Local vis restrictions along inland edge of cloud 
deck. Scatter out Sunday by 17Z.

Mountains/Deserts...Mostly clear through Sunday, but with some 
cumulus clouds over the mountains through 01Z and again Sunday 
between 19-00Z. Bases near 10000 feet MSL.


No hazardous marine weather is expected through Thursday.


Beach Hazard Statement will continue through this evening for 
elevated surf and strong rip currents. A 3-4 ft/15-16 second period 
swell from 180 degrees will bring surf of 3-6 ft, with isolated sets 
to 7 ft, mainly along the south facing beaches of Northern Orange 
County, and strong rip currents. Surf will lower tonight through 


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


CA...Beach Hazards Statement through this evening for Orange County 
     Coastal Areas-San Diego County Coastal Areas.