...HIGH SURF ADVISORY IN EFFECT FROM 9 AM TO 11 PM PDT THURSDAY... The National Weather Service in Seattle has issued a High Surf Advisory, which is in effect from 9 AM to 11 PM PDT Thursday. * WAVES AND/OR SURF...West swell 18 to 20 feet at 15 or 16 seconds. * SOME AFFECTED LOCATIONS...La Push, Pacific Beach, Ocean Shores.