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000 FXUS66 KLOX 202100 AFDLOX SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 200 PM PDT SAT SEP 20 2008 .SHORT TERM (TODAY-TUESDAY)... SOME COLD AIR THAT MOVED OVER THE AREA FROM THE NORTH LAST NIGHT HAS PRODUCED ABOUT 5C OF COOLING...MOSTLY BETWEEN 950MB AND 800MB. THIS HAS SEVERELY WEAKENED THE MARINE INVERSION AND IN TURN WEAKENED THE CONFIDENCE IN THE STRATUS FORECAST. TO THE NORTH...WENT WITH A SIMILAR COVERAGE PATTERN TO WHAT HAPPENED LAST NIGHT...BUT WOULD NOT BE SURPRISED TO SEE FAR LESS COVERAGE...ESPECIALLY WHEN FACTORING IN A BIT OF MORNING NE FLOW. SOUTH OF POINT CONCEPTION...AN EDDY LOOKS FAVORABLE AND SHOULD DEEPEN THE MARINE LAYER ABOVE 2000 FT. EVEN THOUGH THAT DEPTH USUALLY BODES WELL FOR A FULL VALLEY ONSLAUGHT... THE WEAK INVERSION...LACK OF MARINE CLOUD COVERAGE THIS AFTERNOON... AND NEARBY NORTHERLY FLOW PUTS ANY SCENARIO FROM LITTLE STRATUS OVER LAND TO FULL VALLEY COVERAGE POSSIBLE. SOMEWHERE IN BETWEEN SEEMS BEST AT THIS POINT. THE CENTRAL COAST AND ANTELOPE VALLEY ARE SEEING SOME BREEZY CONDITIONS THIS AFTERNOON...WHICH SHOULD ABATE EARLY THIS EVENING. WINDS WILL BE A CONCERN LATER TONIGHT AS WELL...AS WEAK HIGH PRESSURE FORMS TO THE NORTH. GUSTY NORTHERLY WINDS SHOULD FORM THROUGH THOSE SUNDOWNER AREAS OF SBA COUNTY AND THE I5 CORRIDOR. ALTHOUGH NO ADVISORIES ARE EXPECTED AT THIS POINT...SBA COUNTY WILL GET CLOSE...WITH A FEW CANYONS LIKELY EXCEEDING 35 MPH. SOME MOISTURE EMBEDDED IN THE FLOW WILL ALSO HELP TO CREATE SOME CLOUDS ALONG THE NORTH FACING SLOPES. EVEN THROUGH THE MAINLY ZONAL UPPER PATTERN REMAINS UNCHANGED... TEMPS WILL BE DIFFICULT TO FORECAST TOMORROW DUE TO THE UNCERTAINTY IN THE MARINE LAYER. WITH THE CURRENT IDEA OF STRATUS GETTING INTO THE LA AND VTU VALLEYS TOMORROW...WENT WITH A FEW DEGREES OF ADDITIONAL COOLING. WITH THE NORTHEAST FLOW AND POSSIBLE DROP IN STRATUS COVERAGE TO THE NORTH...WENT WITH A FEW DEGREES OF WARMING UP THERE. MIN TEMPS SHOULD REMAIN RATHER CHILLY LIKE THIS MORNING FOR AT LEAST ONE MORE NIGHT. MON AND TUE LOOKS TO KICK OFF AN OVERALL WARM UP AS A TROUGH QUICKLY PASSES THROUGH THE PAC NW SUN NIGHT AND A HEALTHY 590DM HIGH BUILDS IN FROM THE SOUTH. PREVIOUS MODELS RUNS HAVE BEEN FLIP FLOPPING... BUT THE 12Z GFS AND ECMWF ARE CONSISTENT WITH THEIR 0Z COUNTERPARTS AND CONFIDENCE IS ON THE RISE. NORTHERLY WINDS WILL ABATE ON MON THANKS TO THE TROUGH PASSAGE TO THE NORTH. .LONG TERM (WEDNESDAY-SATURDAY)... WITH ONSHORE GRADS WEAKENING AND THE RIDGE CONTINUING ITS BUILD UP FROM THE SOUTH...WED AND THU LOOKS TO REMAIN WARM...WITH ONE OF THOSE DAYS BEING THE WARMEST OF THE WEEK. THE HIGH AND WEAK ONSHORE GRADS SHOULD KEEP THE MARINE LAYER CONFINED TO THE IMMEDIATE COAST AT BEST...WHICH FURTHER HINTS AT A WARM MIDWEEK. THERE IS A WILDCARD IN A WEAK CUTOFF LOW TO THE WEST. THIS PATTERN WILL CREATE AN EAST-WEST TEMP GRAD THAT MODELS CURRENTLY HAVE US SITTING IN THE WARM SECTOR WED AND THU...BUT THIS PATTERN COULD SHIFT AND TEMPS COULD BE A BIT COOLER. NOT ONLY THAT...BUT A WHEN QUESTION EXISTS AS WELL...AS TO WHEN WILL THINGS FINALLY SHIFT TO THE EAST. CURRENTLY THE GFS AND ECMWF ARE BEHAVING NICELY...WITH A TROUGH DIGGING INTO THE LOW TO THE WEST AND PUSHING EVERYTHING EASTWARD ON FRI AND SAT. THIS IS REFLECTED IN THE FORECAST WITH SOME COOLING...BUT CONFIDENCE IS LOW THIS FAR OUT. && .AVIATION...20/2000Z. AN EDDY WILL SPIN UP A MARINE LAYER TONIGHT...BRINGING LOW CLOUDS AND PATCHY FOG WITH MVFR CONDITIONS TO AT LEAST LA AND VENTURA COUNTY COASTAL SECTIONS. OF GREATER UNCERTAINTY IS WHETHER THE LOW CLOUDS AND FOG WILL ALSO SPREAD TO THE SANTA BARBARA SOUTH COAST AND THE LA COUNTY VALLEY TAF SITES. THE CENTRAL COAST AND KPRB ARE LIKELY TO HAVE LOW CLOUDS AND FOG WITH MVFR CONDITIONS OVERNIGHT. KLAX...FAIR TO GOOD CONFIDENCE IN THE CURRENT TAF. CLEAR SKIES UNTIL 07Z WHEN LOW CLOUDS AND PATCHY FOG WILL ARRIVE WITH MVFR CONDITIONS. A 40 PERCENT CHANCE OF LOW CLOUDS AND FOG ARRIVING AS SOON AS 05Z OR AS LATE AS 09Z. THEN LOW CLOUDS AND FOG UNTIL LATE MORNING SUNDAY. KBUR...LITTLE OR NO CONFIDENCE IN THE TAF FORECAST FOR KBUR. A 50 PERCENT CHANCE OF LOW CLOUDS AND FOG ARRIVING AFTER MIDNIGHT...AND A 50 PERCENT CHANCE && .LOX WATCHES/WARNINGS/ADVISORIES... SMALL CRAFT ADVISORY (SEE LAXMWWLOX). && $$ PUBLIC...KITTELL AVIATION...SWEET WWW.WEATHER.GOV/LOSANGELES