Expires:No;;421208 FXUS66 KSGX 200934 AFDSGX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN DIEGO CA 300 AM PDT MON MAY 20 2013 .SYNOPSIS... HIGH PRESSURE WILL PREVAIL OVER SOUTHERN CALIFORNIA TODAY AND TUESDAY BRINGING WARMER DAYS AND LESS EXTENSIVE COASTAL CLOUDS. LOCALLY GUSTY OFFSHORE WINDS ARE EXPECTED THIS MORNING NEAR THE FOOTHILLS. HIGH PRESSURE WILL BE REPLACED BY A LOW PRESSURE TROUGH ALONG THE WEST COAST BY MIDWEEK. EXPECT COOLER WEATHER...MORE EXTENSIVE COASTAL CLOUDS AND GUSTY WINDS IN THE MOUNTAIN PASSES AND ADJACENT DESERTS. THE TROUGH WILL WEAKEN HEADING INTO THE WEEKEND ALLOWING SLIGHTLY WARMER WEATHER AND LESS EXTENSIVE LOW CLOUDS. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... LOW CLOUDS HAVE BEEN SLOW TO DEVELOP ALONG THE COAST THIS MORNING...BUT SEEM TO BE ORGANIZING THEMSELVES PRETTY WELL EARLY THIS MORNING. A WEAK COASTAL EDDY CIRCULATION SEEMS TO BE HELPING THE PROCESS. A SHORTWAVE MOVING THROUGH NEVADA AND UTAH WILL PRODUCE SOME OFFSHORE FLOW THIS MORNING...ENOUGH FOR A FEW DECENT BREEZES IN THE USUAL FAVORED FOOTHILL AND ADJACENT VALLEY LOCATIONS. THIS WILL ALSO BRING IN DRYER AIR TO THE VALLEYS AND ALLOW THE TEMPS TO JUMP UP DURING THE DAY. 90S WILL BE COMMON IN THE INLAND EMPIRE. BUT JUST AS QUICKLY...THE FLOW WILL TURN ONSHORE THIS AFTERNOON AND THE SEA BREEZE WILL TAKE OVER. THE COASTAL EDDY CIRCULATION WILL ONLY STRENGTHEN OVER THE NEXT FEW DAYS AS A BIG TROUGH OF LOW PRESSURE DROPS DOWN THE WEST COAST. THIS WILL DEEPEN THE MARINE LAYER AND SEND THE CLOUDS INTO THE VALLEYS EACH NIGHT AND MORNING FOR SEVERAL DAYS. AREAS OF FOG WILL DEVELOP ALONG THE INLAND EXTENT OF THE CLOUD DECK. SOME THOUGHT HAS BEEN GIVEN TO WHETHER THE LOW CLOUDS WILL STICK TO THE BEACHES DURING THE DAYS THIS WEEK. THE MARINE INVERSION AND ONSHORE FLOW WILL BE STRONG...GOOD INDICATORS FOR PERSISTENT COASTAL CLOUDS. BUT WE HAVE YET TO CREATE AN EXTENSIVE LOW CLOUD DECK OFF THE COAST...ANOTHER GOOD INDICATOR. FOR NOW WE WILL GO WITH DECENT PARTIAL IF NOT FULL CLEARING AT THE COAST UNTIL MORE CLUES ARE FORTHCOMING. THIS BIG WEST COAST TROUGH WILL ALSO PRODUCE STRONG GUSTY WINDS THROUGH MOUNTAIN PASSES AND ADJACENT DESERTS EACH AFTERNOON THROUGH EVENING TUESDAY THROUGH AT LEAST FRIDAY. WEDNESDAY AND THURSDAY SHOW THE MOST PROMISE FOR THE STRONGEST WINDS THAT WILL AT LEAST APPROACH OR EVEN MEET WIND ADVISORY CRITERIA. TEMPS WILL BE ON THE COOL SIDE OF NORMAL FOR A WHILE. THE TROUGH WEAKENS FRIDAY...BUT SHORTWAVES ROTATING THROUGH THE BIG LONGWAVE TROUGH CONTINUE THROUGH THE WEEKEND. THAT WILL KEEP US COOL WITH SEMI EXTENSIVE LOW CLOUDS EACH NIGHT AND MORNING. TYPICAL SPRING WEATHER. && .AVIATION... 200915Z...COAST/VALLEYS...STRATUS WITH BASES 1000-1500 FT MSL AND TOPS TO 2000 FT WILL CONTINUE TO FILL IN ALONG THE COAST AND SPREAD 10-15 SM INLAND THIS MORNING. LOCAL VSBY 3-5SM POSSIBLE OVER HIGHER COASTAL TERRAIN. STRATUS/VIS RESTRICTIONS WILL CLEAR TO THE COAST BETWEEN 15Z AND 17Z. STRATUS WILL RETURN TO THE COASTAL AIRPORTS 03-06Z WITH SIMILAR BASES AND TOPS. MTNS/DESERTS...MOSTLY CLEAR WITH UNRESTRICTED VSBY THROUGH TUE MORNING. && .MARINE... A 3 FOOT 16-17 SEC PERIOD SW SWELL WILL CONTINUE THROUGH MIDWEEK...GENERATING ELEVATED SURF AND STRONG RIP CURRENTS ALONG SOUTHWEST FACING BEACHES. HIGHEST SURF OF AROUND 4 TO 6 FT WITH LOCAL SETS TO AROUND 7 FEET ARE POSSIBLE ON EXPOSED SOUTHWEST FACING BEACHES. A 6 TO 8 FOOT SHORT-PERIOD NORTHWEST SWELL WILL MOVE INTO THE OUTER COASTAL WATERS WEDNESDAY AND THURSDAY...CREATING CHOPPY SEAS IN AREAS SOUTH AND WEST OF SAN CLEMENTE ISLAND. && .FIRE WEATHER... A BRIEF SHOT OF OFFSHORE FLOW WILL TAKE PLACE THIS MORNING. LOCALIZED NORTHEAST WINDS THROUGH PASSES AND CANYONS WILL BRING LOWER DEW POINTS INTO INLAND VALLEYS AND FOOTHILLS. RELATIVE HUMIDITY VALUES WILL FALL BELOW 15 PERCENT DURING THE DAY AS TEMPS RISE WITH DRY AIR EFFICIENCY. ONSHORE FLOW AND THE SEA BREEZE WILL QUICKLY ANSWER THIS AFTERNOON SPREADING HIGHER DEW POINTS AND HUMIDITY INLAND. && .SGX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ PUBLIC/FIRE...MM AVIATION/MARINE...SS