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Area Forecast Discussion (AFD)

Issued by San Diego, CA (SGX)

FXUS66 KSGX 170436 AAA

Area Forecast Discussion
National Weather Service San Diego CA
930 PM PDT Thu May 16 2019

The persistent west coast trough continues to be the strong driver 
for the weather in the southwest. Persistent, mainly onshore flow 
will continue to weaken and strengthen at times due to Pacific 
frontal systems moving through the main trough position and into 
Southern California. Periods of showers should accompany the mainly 
weak Pacific storms. Decreasing showers this evening and Friday 
morning is expected, with additional drying expected Friday into 
Saturday, but then then another similar low will bring another 
period of cooling, gusty winds, and precipitation for Sunday into 
early Monday. By late Monday drying and warming is expected. Yet 
another low pressure system is expected for the middle part of next 
week that will bring more cooling, gusty winds, and additional 
chances of precipitation Southern California.



Evening Update: No changes were made to the forecast this evening. 
Isolated showers will continue overnight in post front environment 
with continued brisk NW flow. Winds will remain gusty over the 
mountains and deserts through Friday morning with patchy blowing 
dust. Onshore flow will remain healthy but a weak marine inversion 
should mean mainly scattered low clouds will continue overnight.

Previous Short Term Discussion: The west coast trough has pretty 
much decided that winter weather will continue deep into spring in 
SOCAL as the the jet remains rather robust in the area. The mainly 
decaying cold fronts are remaining strong enough to bring some light 
to moderate precipitation to the area at times. Occasional showers 
will linger near the mountains into the evening and for areas of San 
Diego County from the coast tonight into Friday morning. Additional 
amounts should generally be around a trace. 


.LONG TERM (Sunday through Wednesday)...
Ensembles and the local WRF model continue to indicate that the next 
low pressure system is expected to arrive on Sunday bringing another 
round of cooling, precipitation, and gusty winds for Sunday and 
early Monday. For late Monday into Tuesday, it will be drier and a 
little warmer under weak high pressure. For Wednesday and Thursday, 
the mean trough of low pressure will be centered in the vicinity of 
the southwest states with below average temperatures, gusty winds in 
the mountains and deserts, and additional chances of precipitation. 


170330Z...Coast/Valleys...SCT clouds with bases around 2500-4500 ft 
MSL. Cigs expected to form inland mainly in San Diego County after 
10Z with bases 2500-3500 ft MSL. Low clouds expected to form near 
the coast after 12Z with bases 2000-2500 ft MSL. Higher terrain will 
be obscured in areas of low clouds. Scatter out expected after 17Z 

Mountains/Deserts...Winds expected to decrease overnight before 
picking up again tomorrow after 18Z. West winds with gusts of 20-25 
kt expected and MOD UDDFS possible.  


A Small Craft Advisory is in effect through 11 PM Friday evening for 
strong westerly winds with gusts 25-30 kts. Brisk winds Saturday 
afternoon will gust over 20 kts. Winds will increase again Sunday 
through Monday with hazardous boating conditions possible.


CA...Wind Advisory until 11 AM PDT Friday for Apple and Lucerne 
     Valleys-Coachella Valley-Riverside County Mountains-San 
     Bernardino County Mountains-San Diego County Deserts-San 
     Diego County Mountains-San Gorgonio Pass Near Banning.

PZ...Small Craft Advisory until 11 PM PDT Friday 
     for Coastal Waters from San Mateo Point to the Mexican 
     Border and out to 30 nm-Waters from San Mateo point to the 
     Mexican Border Extending 30 to 60 nm out including San 
     Clemente Island.