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Area Forecast Discussion (AFD)

Issued by San Diego, CA (SGX)

FXUS66 KSGX 240406

Area Forecast Discussion
National Weather Service San Diego CA
910 PM PDT Sat Mar 23 2019

A weak trough will deepen the marine layer tonight for more 
extensive low clouds west of the mountains. High pressure building 
aloft on Sunday will bring warmer days through Monday. Cooler again 
midweek as a Pacific trough moves inland across central California. 
The system may generate a few showers over southern California, but 
amounts will be light. Increasing onshore flow will bring a return 
of cooler weather and gusty winds in the mountains and deserts. The 
weather continues to look uncertain for the end of next week, but 
largely dry.



Highs today were remarkably similar to yesterday at nearly all 
reporting coastal, valley and mountain stations. Fullerton (67), 
Newport Beach (62), Ontario (69), Corona (66), Rancho Bernardo (64) 
and Idyllwild (54) were all the same as yesterday. Fifteen other 
stations were within 1 degree of yesterday.  

Low clouds were expanding over the inland basin and the foothills 
this evening. Cloud bases were 1,500 feet with tops around 3,000 
feet. A weak trough passing by over San Bernardino County may 
generate a shower or two tonight over the mtn slopes, but chances 
are small. 

Sunday will be 4 to 8 degrees warmer than today as high pressure 
aloft increases 500 mb heights by 30 decameters. The exception to 
this degree of warming will be in the coastal areas where the 
proximity to 60 degree ocean water temperatures and the afternoon 
sea breeze will limit warming to only a couple degrees. Monday will 
be even warmer as heights rise another 20-30 decameters. 

*From Previous Discussion*

It will remain mild on Tuesday as high clouds thicken ahead of a 
stronger EastPac storm for midweek. This one will bring significant 
rain/snow to central and northern CA, and may brush SoCal with some 
light showers as well but POPS are low this far south and any 
amounts are expected to be light.

The outlook remains rather murky for the latter half of next week 
and into the weekend. The 12Z operational runs of the ECMWF and GFS 
remain out of phase across the West. GFS operational runs have been 
more consistent with it's ensemble mean, while the ECMWF operational 
runs have deviated more from it's ensemble mean. So, if there is a 
model to favor around the end of next week, the GFS would be a 
slight favorite. It appears as though the GFS model runs are holding 
onto the GOA ridge better than the ECMWF a swell, which may be the 
way to go, keeping the energy in the westerlies directed over more 
southern latitudes. Favoring the GFS would keep it much cooler but, 
like the ECMWF, largely dry.  


230300Z...BKN-OVC stratus with bases 1200-1800 ft MSL and tops to 
3000 ft MSL will affect the terminals through 24/15Z, after which 
bases will rise with most terminals clearing to FEW-SCT near 2500 ft 
MSL by 17-18Z. Areas of vis 3-5 SM on obscured coastal slopes and 
mesas overnight with isolated spots to 1 SM or less, though 
terminals should remain unaffected. SCT-BKN high clouds AOA 20000 ft 
MSL tonight, gradually clearing tomorrow leading to mostly CLR skies 
by the afternoon.

Mountains/Deserts...BKN-OVC low clouds will obscure mountain slopes 
overnight with local vis 3-5 SM through 16Z. Winds will gradually 
subside overnight, however isolated SFC gusts to 30 kts will be 
possible, along with LGT-MOD UDDFTS over and east of the mtns. 
Deserts will remain CLR minus FEW-SCT high clouds AOA 20000 ft MSL 
overnight. Expect weaker SFC winds in valleys tomorrow, with gusts 
below 15 kts. 


Long-period 16 second swell will continue to bring combined seas to 
8-9 ft in the outer waters overnight and into tomorrow. The swell 
will begin to subside in the afternoon. Otherwise, no hazardous 
marine weather is expected through Thursday.


A west-northwest swell of 6-8 ft from 290 degrees, combined with a 
15-17 second period could generate high surf through tomorrow with 
sets to 8 ft possible, mainly in southern San Diego County. A High 
Surf Advisory is in effect for Orange and San Diego Counties through 
9 PM Sunday. &&

Skywarn activation will not be needed this weekend. 


CA...High Surf Advisory until 9 PM PDT Sunday for Orange County 
     Coastal Areas-San Diego County Coastal Areas.