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000 FXUS66 KLOX 142350 AAA AFDLOX SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATE NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 450 PM PDT SUN SEP 14 2008 UPDATE FOR NEW AVIATION DISCUSSION .SHORT TERM (TODAY-WED)...INVERSION IS LOWERING AS HIGH PRESSURE BUILDS OVER THE STATE. MARINE LYR DEPTH THIS MORNING WAS AROUND 1800 FT AND THIS IS EXPECTED TO DROP ABOUT IN HALF TONIGHT. IN ADDITION, ONSHORE FLOW IS WEAKER TODAY AS SURFACE HIGH PRESSURE INCREASES INLAND. THE RESULT WILL BE MUCH LESS OF AN INLAND PUSH OF THE LOW CLOUDS TONIGHT AND AN EARLIER BURN OFF ON MONDAY. DAYTIME TEMPS WILL ALSO INCREASE BY SEVERAL DEGREES IN MOST AREAS, ESPECIALLY THE VALLEYS WHERE TEMPS HAVE BEEN KEPT IN CHECK BECAUSE OF THE MARINE INFLUENCE. BOTH THE NAM AND GFS SHOW THE OFFSHORE FLOW INCREASING TUESDAY WHILE THE AIRMASS REMAINS VERY WARM. IF THIS COMES TO FRUITION, HIGHS ON TUESDAY AT LOWER ELEVATIONS SHOULD BE 5-8 DEGREES WARMER THAN MONDAY, PUSHING WARMER VALLEY HIGHS WELL ABOVE 100 AND DOWNTOWN LA IN THE MID 90S. HOWEVER, THE MODELS HAVE BEEN CONSISTENT SHOWING AN UPPER LOW OFF THE COAST OF NRN CA WITH A TROF EXTENDING SOUTH TOWARDS SRN CA. IT`S UNUSUAL TO HAVE OFFSHORE GRADIENTS OF -2 MB LAX-DAG AND 950 TEMPS NEAR 32C ACROSS THE LA BASIN WITH A TROF ALONG THE COAST. MOS GUIDANCE HIGHS HAVE BEEN RUNNING ON THE COOL SIDE FOR TUE POSSIBLY DUE TO THE TROF. BUT GENERALLY SPEAKING THE COMBINATION OF THE OFFSHORE FLOW AND VERY WARM LOW LVL TEMPS WOULD RESULT IN HIGHS TOPPING 100 IN THE VALLEYS AND IN THE 90S ACROSS THE INLAND COASTAL PLAIN. WILL KEEP HIGHS WELL ABOVE MOS FOR NOW. MODELS ALSO SHOW A VERY THIN LAYER OF MID LEVEL MOISTURE BEING PULLED UP FROM THE SOUTH ON TUESDAY. THERE ISN`T ENOUGH MOISTURE TO WARRANT ADDING CONVECTION TO THE FORECAST, BUT WITH LI`S DROPPING BELOW ZERO IN THE LA COUNTY MOUNTAINS AND SURFACE TEMPS RISING WELL INTO THE 90S WE COULD SEE SOME AFTERNOON CLOUDS ACROSS THE INTERIOR. WILL GO WITH PARTLY CLOUDY INLAND TUESDAY AFTERNOON WITH POPS AT OR BELOW 10 AND CLEAR ELSEWHERE. OFFSHORE FLOW TURNS ONSHORE WEDNESDAY, BUT WEAK ENOUGH SO THAT CLOUDS SHOULD REMAIN OUT OF THE VALLEYS. HOWEVER, COOLER MARINE AIR WILL BRING DAYTIME HIGHS DOWN SEVERAL DEGREES AT LOWER ELEVATIONS WITH TEMPS IN THE MOUNTAINS AND DESERTS ALSO COOLING DUE TO LOWER THICKNESSES. .LONG TERM (THU-SUN)...COOLING TREND TO CONTINUE THROUGH THURSDAY BRINGING DAYTIME HIGHS DOWN TO NEAR NORMAL LEVELS. THEN LITTLE CHANGE EXPECTED FRIDAY. OVER THE WEEKEND THE TROF FINALLY MOVES INLAND THROUGH THE PAC NW AND HEIGHTS/THICKNESSES RISE SLIGHTLY ACROSS SRN CA. ONSHORE FLOW ALSO WEAKENS, ESPECIALLY BY SUNDAY SO WE COULD SEE A FEW DEGREES OF WARMING NEXT WEEKEND. FOR NOW THOUGH CONFIDENCE ISN`T HIGH ENOUGH TO GO AGAINST PERSISTENCE SO WILL STICK WITH SIMILAR CONDITIONS THROUGH THE WEEKEND. && .AVIATION...14/2340Z...MARINE LAYER HAS FALLEN TO NEAR 1200 FT DEEP AT KLAX. WITH THE MARINE LAYER EXPECTED TO CONTINUE LOWERING SOME OVERNIGHT IT LOOKS LIKE LOW CLOUDS SHOULD NOT MOVE INTO THE VALLEY TAF SITES TONIGHT AND MON. IT LOOKS LIKE MODERATE CONFIDENCE THAT LOW CLOUDS AND IFR TO LIFR CONDITIONS WILL EVENTUALLY MOVE BACK INTO MOST COASTAL TAF SITES TONIGHT. THE TIMING IS PROBLEMATIC CONSIDERING THE CLEARING PATTERN OF THE LOW CLOUDS THIS AFTERNOON OFF THE CENTRAL COAST AND THE CLEARING TREND ALONG THE COAST S OF POINT CONCEPTION. OVERALL...MOST COASTAL TAF SITES SHOULD HAVE THE LOW CLOUDS AND FOG MOVE IN FROM ABOUT 05Z TO 07Z. THE LOW CLOUDS AND FOG WITH IFR AND SOME LIFR CONDITIONS WILL PREVAIL UNTIL ABOUT 16Z TO 17Z MON...THEN VFR CONDITIONS SHOULD DEVELOP FROM LATER MON MORNING THRU THE AFTERNOON. MODERATE TO HI CONFIDENCE THE TAF SITES AWAY FROM THE COAST WILL HAVE VFR CONDITIONS THRU MON. FOR KLAX...MODERATE CONFIDENCE IFR CIGS WILL MOVE INTO THE AIRFIELD AROUND 06Z...BUT COULD BE DELAYED UNTIL 07Z OR 08Z. THE LOW CLOUDS WILL CLEAR OFF THE COAST TO VFR CONDITIONS BY ABOUT 16Z MON...THEN CLEAR CONDITIONS WILL PREVAIL THRU MON AFTERNOON. NO WIND ISSUES EXPECTED THRU MON. FOR KBUR...MODERATE CONFIDENCE VFR CONDITIONS WILL PREVAIL THROUGH MON. NO WIND ISSUES ARE EXPECTED THRU THE PERIOD. && .LOX WATCHES/WARNINGS/ADVISORIES... RED FLAG WARNING (SEE LAXRFWLOX). FIRE WEATHER WATCH (SEE LAXRFWLOX). SMALL CRAFT ADVISORY (SEE LAXMWWLOX). && $$ PUBLIC...WOFFORD AVIATION...SIRARD WWW.WEATHER.GOV/LOSANGELES