000 FXUS66 KSGX 040958 AFDSGX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN DIEGO CA 300 AM PDT SAT JUL 4 2009 .SYNOPSIS... THE MARINE LAYER AND ONSHORE FLOW WILL CONTINUE COASTAL LOW CLOUDS AND FOG DURING THE NIGHTS AND MORNINGS...EXTENDING LOCALLY INLAND. RESIDUAL MID LEVEL MOISTURE MAY BRING A FEW AFTERNOON CLOUDS TO THE MOUNTAINS TODAY...OTHERWISE FAIR WITH SEASONAL TEMPERATURES THROUGH MONDAY. SLIGHTLY STRONGER ONSHORE FLOW FOR MID WEEK WITH SLIGHT COOLING AND GUSTY ONSHORE AFTERNOON AND EARLY EVENING WINDS IN THE MOUNTAINS AND DESERTS. FOR LATE IN THE WEEK...HIGH PRESSURE OVER THE INTERIOR SOUTHWEST STATES MAY BRING SOME WARMING AND SOME RETURN OF MID LEVEL MOISTURE AND AFTERNOON CLOUDS OVER THE MOUNTAINS. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .SHORT TERM (TODAY THROUGH TUESDAY)... INTERIOR HIGH PRESSURE EXTENDING INTO SOUTHERN CALIFORNIA WILL CHANGE LITTLE THROUGH MONDAY...BUT SOUTHWEST FLOW ALOFT WILL CONTINUE THE DRYING OF RESIDUAL MID LEVEL MOISTURE WITH FEWER AFTERNOON CLOUDS ON THE DESERT SLOPES OF THE MOUNTAINS. THE MARINE LAYER IS NEAR 1300 FEET DEEP. SATELLITE IMAGERY SHOWS STRATUS MOST EXTENSIVE CURRENTLY ALONG THE SAN DIEGO COUNTY COAST...BUT SOME INCREASE IN COVERAGE IS EXPECTED OVER THE OUTER COASTAL WATERS AND ORANGE COUNTY COASTAL AREAS THROUGH SUNRISE. LITTLE CHANGE IN THE OVERALL STRATUS PATTERN THROUGH MONDAY WITH STRATUS GRADUALLY SPREADING INLAND OVERNIGHT INTO THE LOWER COASTAL VALLEYS AND CLEARING TO NEAR THE BEACHES EACH MORNING. HOWEVER WITH WEAK ONSHORE FLOW AND A STRONG INVERSION ALOFT...PATCHY STRATUS COULD LINGER NEAR SOME BEACHES INTO EACH AFTERNOON. FOR TUESDAY...SLIGHT WEAKENING OF HIGH PRESSURE ALOFT AND SLIGHT STRENGTHENING OF ONSHORE FLOW SHOULD BRING MINOR COOLING AND MINOR DEEPENING OF THE MARINE LAYER. && .LONG TERM (WEDNESDAY THROUGH SATURDAY)... A LITTLE STRONGER ONSHORE SLOW SHOULD BRING MINOR COOLING...SLIGHT DEEPENING OF THE MARINE LAYER...AND LOCALLY GUSTY ONSHORE AFTERNOON AND EARLY EVENING WINDS IN THE MOUNTAINS AND DESERTS FOR WEDNESDAY AND THURSDAY. FOR FRIDAY INTO THE WEEKEND...THE TROUGH OF LOW PRESSURE ALONG THE WEST COAST MAY BEGIN TO WEAKEN AS HIGH PRESSURE OVER ARIZONA AND NEW MEXICO BEGINS TO STRENGTHEN AND EXPAND WESTWARD. THIS WOULD BRING WARMING AND SOME RETURN OF MID LEVEL MOISTURE WITH AFTERNOON CLOUDS FOR THE MOUNTAINS. && .AVIATION... 040930Z...THE MARINE LAYER DEPTH EARLY THIS MORNING WAS AROUND 1300 FEET. LITTLE CHANGE IN THE MARINE LAYER DEPTH IS EXPECTED THROUGH SUNDAY. STRATUS WAS CONFINED TO THE IMMEDIATE COAST BUT WAS BEGINNING TO SPREAD INTO THE LOWER COASTAL VALLEYS IN SAN DIEGO COUNTY. STRATUS COULD REACH KSNA BY SUNRISE. STRATUS SHOULD BREAK UP BY 16Z NEAR KSNA AND BETWEEN 16Z AND 18Z FROM KCRQ TO KSAN. EXPECT STRATUS TO RETURN TO THE COASTAL AREAS AFTER SUNSET AND SPREAD LOCALLY INLAND BY MIDNIGHT. ABOVE THE MARINE LAYER...SOME AFTERNOON CU EXPECTED OVER THE MOUNTAINS WITH BASES NEAR FL090...OTHERWISE A MOSTLY CLEAR SKY WITH UNRESTRICTED VISIBILITIES WILL CONTINUE THROUGH SUNDAY. HORTON && .SGX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && $$ PUBLIC...MARTIN AVIATION/MARINE...HORTON NWS ON THE WEB AT WEATHER.GOV/SANDIEGO