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Area Forecast Discussion (AFD)

Issued by San Diego, CA (SGX)

FXUS66 KSGX 161540

Area Forecast Discussion
National Weather Service San Diego CA
839 AM PDT Sun Jun 16 2019

Weak low pressure aloft will maintain typical June weather with near 
to slightly below normal daytime temperatures and marine clouds and 
fog spreading well inland each night. Midday clearing back to 
coastal areas is expected, but clearing may be delayed or limited 
some days due to fluctuations in the marine layer and cloud depth. 
The deserts will be seasonably hot under fair skies. Slight warming 
is possible mid next week as a ridge attempts to build aloft, but a 
return to cooler weather is likely before next weekend. 



Once again, the offshore waters spanning the entire CA Coast is a 
sea of stratus extending hundreds of miles west. The stratus also 
extended deep into the valleys early this morning. The 12Z Miramar 
sounding had the marine inversion based near 2550 FT MSL and topped 
by a strong 11C inversion. The sfc pressure gradient remained 
onshore but was weak, along with reported winds.

The inversion is roughly 750 FT lower than yesterday at Miramar. 
Pilot reports to the north suggest about 600 FT lower. The cloud 
deck overall is thinner as well (1000-1200FT), which suggests 
earlier clearing well inland. Also, max temps may jump higher by 
late morning at the base of the coastal slopes (around 3500 FT) 
where temps have spiked by around 6C over yesterday. Complete  
clearing still is questionable over coastal areas, which are 
more likley to see limited/variable amounts of sun this afternoon. 
Overall though, the forecast looks to be on track so no changes.

From previous discussion...

Max temps today will be similar to yesterday except in the high 
desert where a couple degrees of cooling will take place as an upper 
level trough approaches the region this afternoon.

A series of weak shortwaves will maintain the troughy pattern over
the region through Tuesday. This will keep temperatures fairly
uniform each day with extensive marine layer induced cloudiness
developing each evening and spreading through the valleys. 

By Wednesday, a high pressure ridge over the East Pac will nose
into Central California, bringing some warming to our region,
especially for the mountains and deserts. The ridge will gradually
weaken and the ensemble and deterministic model forecasts seem to
be in better agreement that the ridge will be short lived, as a
longwave trough from the Pac NW drops into the Great Basin by
Friday and into next weekend, bringing a return to slightly cooler
than normal conditions and a return of the deeper, more seasonal,
marine layer and stronger inversion for SoCal. 

Deeper troughing over the SW will likely bring stronger diurnal 
wind patterns once again, as we had seen a few days ago, with 
onshore gusts up around 50 mph in the more wind favored passes and
canyons. The SW troughy pattern could hang around into the
following week as well. 


161515Z...Coast/Valleys...Widespread low clouds with bases 1000-1600 
ft MSL expected to clear valleys 16-19Z, with intermittent clearing 
along the coast after 19Z. Low clouds with bases 1000-1600 ft MSL, 
expected to spread inland overnight. Local vis restrictions of 3-5 
SM in BR/HZ in the valleys and higher terrain obscured in clouds. 

Mountains/Deserts...Mostly clear with unrestricted vis today. West 
winds with sfc gusts 25-35 kt will occur along the mountain crests 
and desert mountain slopes and below the passes from 22-04Z, 
weakening overnight. Areas of up/down drafts are possible over and 
east of the mountains.


No hazardous marine conditions are expected through Thursday. 


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