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000 FXUS66 KLOX 200324 AFDLOX SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 820 PM PDT FRI SEP 19 2008 .SHORT TERM (TODAY-MON)... TEMPERATURES COOLED DOWN RATHER SIGNIFICANTLY ACROSS PORTIONS OF THE SLO INTERIOR VALLEYS WHERE PASO ROBLES ONLY REACHED 76 DEGREES TODAY. MOST OTHER INTERIOR LOCATIONS WERE DOWN BETWEEN 3-5 DEGREES AS BOUNDARY LAYER TEMPS COOLED A BIT AND THICKNESS LVLS DROPPED IN THE WAKE OF A WEAK FRONTAL BOUNDARY THAT MOVED INLAND OVERNIGHT. MOST LA/VTU SBA COUNTY VALLEYS REMAINED IN THE 80S. WHILE LOW CLOUDS WERE ABSENT OVERNIGHT AND THIS MORNING...DOWNTOWN WAS ABLE WARM UP AS HIGH AS PALMDALE TO 86 DEGREES. CURRENTLY...SKIES ARE MOSTLY CLEAR SOUTH OF POINT CONCEPTION...WHILE A BAND OF CLOUDS ASSOCIATED WITH A WEAK TROF WITH CIGS OF NEAR 5000 FT IS BEGINNING TO SURGE INTO THE CENTRAL COAST THIS EVENING. HARD TO TELL THE EXTENT OF CLOUD COVERAGE OVERNIGHT...BUT MODELS SUGGEST THAT CLOUDS SHOULD MOVE INTO THE SALINAS RIVER VALLEY OVERNIGHT. NOT ANTICIPATING ANY FOG DUE TO HIGH CLOUD BASES. LATEST AMDAR SOUNDING NEAR KLAX INDICATED MARINE LAYER NEAR 800 FT...BUT WITH APPROACHING WEAK TROF...MARINE LAYER SHOULD DEEPEN WHILE INVERSION WEAKENS OVERNIGHT. NAM-WRF IS ADVERTISING EDDY CIRCULATION TO HELP SPIN UP SOME STRATUS ACROSS LA/VTU COUNTY COASTAL AREAS OVERNIGHT. FEEL THAT THERE WILL BE SOME PATCHY LOW CLOUDS ACROSS LA COUNTY AFTER MIDNIGHT...AND POSSIBLY VTU COUNTIES. WITH INVERSION WEAKENING...LOW CLOUDS COULD POP UP RANDOMLY ACROSS PORTIONS OF LA/VTU COUNTY COASTAL AREAS...BUT SHOULD REMAIN PATCHY IN NATURE. KEPT SKIES CLEAR FOR SBA SOUTH COAST OVERNIGHT...BUT WITH A FEW BANDS OF CLOUDS NEAR POINT CONCEPTION...A MINI EDDY COULD DEVELOP BETWEEN SBA AND THE CHANNEL ISLANDS LATER TONIGHT. HOWEVER...THERE IS A DECENT NORTHERLY GRADIENT BETWEEN KSBA-KSMX WHICH SHOULD KEEP THE SANTA BARBARA SOUTH COAST CLEAR. SATURDAY LOOKS TO BE A FEW DEGREES COOLER...ALTHOUGH 950 MB TEMPS DO NOT CHANGE MUCH...BUT ONSHORE FLOW INCREASES ACROSS THE REGION. EXPECT MOST VALLEY LOCATIONS TO BE IN THE MID 80S. WHILE THE COASTAL AREAS REMAIN FROM THE UPPER 60S AND 70S TO AROUND 80 INLAND AREAS. A MORE IMPRESSIVE EDDY DEVELOPS ACROSS THE SO CAL BIGHT SAT NIGHT AND SHOULD REACH" onClick="return popup(this, 'notes')">REACH THE COASTAL VALLEYS KEEPING TEMPS COOLER THAN AVG ON SUNDAY. THERE CONTINUES TO BE A DECENT NORTHERLY GRADIENT AFFECTING THE SANTA BARBARA COUNTY MTNS AND SBA SOUTH COAST WHICH SHOULD BRING ADDITIONAL LOCAL GUSTY NORTHWEST TO NORTH WINDS ACROSS THE USUAL WINDY PASSES AND CANYONS NEAR GAVIOTA TO MONTECITO. MODELS ALSO PICK UP SOME LOCAL NORTHERLY WINDS 15 TO 30 MPH ACROSS THE I-5 CORRIDOR LATE SAT NIGHT INTO EARLY SUNDAY MORNING WITH A FEW CLOUDS POSSIBLE PUSHED UP AGAINST THE NRN SLOPES OF THE VTU/WESTERN LA COUNTY MTNS EARLY SUNDAY MORNING. THERE COULD BE A FEW DEGREES OF WARMING ACROSS THE INTERIOR PORTIONS OF THE FORECAST AREA AS WEEK UPPER RIDGE SLOWLY BUILDS IN FROM THE SOUTHWEST. HOWEVER A CATALINA EDDY SHOULD PERSIST SUNDAY NIGHT INTO MONDAY CONTINUING TO LEAVE THE COASTAL AREAS RELATIVELY COOL FOR MONDAY. ...FROM PREVIOUS DISCUSSION... .LONG TERM (TUE-FRI)...WARMING TREND STILL ON TRACK FOR THE MIDDLE OF NEXT WEEK. GFS HAS BACKED OFF SLIGHTLY ON THE OFFSHORE FLOW FOR WED AND THU BUT GRADIENTS SHOULD AT LEAST BE NEAR NEUTRAL IF NOT SLIGHTLY OFFSHORE. STILL THINK THE GFS IS UNDERDOING THE WARMING AT 950 AS WELL THE MOS GUIDANCE HIGHS. GIVEN THE STRENGTH OF THE UPPER HIGH AND NEAR NEUTRAL OR SLIGHTLY OFFSHORE SURFACE GRADIENTS, HIGHS SHOULD BE CLOSE TO 100 IN THE VALLEYS AND CLOSE TO 90 ACROSS THE INLAND COASTAL PLAIN. FOR THIS REASON CURRENT FORECAST CONTINUES TO BE WARMER THAN MOS GUIDANCE. WARMING TREND SHOULD END FRI AS ANOTHER TROF APPROACHES THE COAST AND HIGH PRESSURE MOVES EAST. && .AVIATION...19/1915Z. A VERY LOW CONFIDENCE FORECAST FOR THE COASTAL TAFS. A TROUGH ALONG THE WEST COAST WILL DRAG A WEAK FRONT WITH SOME LOW CLOUDS INTO THE COASTAL WATERS LATER TODAY AND TONIGHT. COASTAL TAFS WITH THE GREATEST VULNERABILITY TO LOW CLOUDS AND FOG MAY EXPERIENCE PATCHY LOW CLOUDS AND FOG TONIGHT. THE TIMING OF THE LOW CLOUDS WILL BE VERY DIFFICULT TO PINPOINT...BUT WILL PROBABLY OCCUR EARLY THIS EVENING ON THE CENTRAL COAST AND LATER OR NOT AT ALL SOUTH OF POINT CONCEPTION. VALLEY TAFS ARE EXPECTED TO BE CLEAR THROUGH SATURDAY. KLAX...A 40 PERCENT CHANCE OF LOW CLOUDS AND FOG WITH MVFR CONDITIONS AFTER MIDNIGHT...OTHERWISE MOSTLY CLEAR. KBUR...HIGH CONFIDENCE IN CLEAR SKIES THROUGH SATURDAY. && .LOX WATCHES/WARNINGS/ADVISORIES... SMALL CRAFT ADVISORY (SEE LAXMWWLOX). && $$ PUBLIC...KAPLAN/WOFFORD AVIATION...SWEET WWW.WEATHER.GOV/LOSANGELES