977 FXUS66 KLOX 071250 AFDLOX SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 450 AM PST SAT NOV 7 2009 .SYNOPSIS...VARIABLE CLOUDINESS AND COOLER TEMPERATURES WILL CONTINUE TODAY AS WEAK LOW PRESSURE SYSTEM SLOWLY EXITS THE REGION. HIGH PRESSURE BUILDING OVER THE AREA TONIGHT WILL ALLOW OFFSHORE FLOW TO ESTABLISH TONIGHT...WARMING AND DRYING THE AIR MASS FOR EARLY NEXT WEEK. ANOTHER TROUGH SHOULD MOVE INTO THE REGION FOR LATE NEXT WEEK. && .SHORT TERM (TODAY-MONDAY)...A CUTOFF TROUGH REMAINS TO THE SOUTHEAST OF THE AREA THIS MORNING...WHILE A WEAK SHORTWAVE TROUGH PUSHES OVER THE AREA. THE SHORTWAVE TROUGHS COLD FRONTAL BOUNDARY IS FALLING APART AT POINT CONCEPTION...STRETCHING CURRENTLY FROM NEAR SAN NICOLAS ISLAND NORTH THROUGH THE SANTA BARBARA CHANNEL AND NORTHEAST TO KPTV IN THE SAN JOAQUIN VALLEY. AS EXPECTED COLD AIR ADVECTION OVER THE COASTAL WATERS IS WIPING AWAY THE STRATUS...BUT THE OROGRAPHICS ON THE LAND MASS ARE ALLOWING STRATOCUMULUS TO REMAIN THIS MORNING. CLOUD COVER WAS INCREASED FOR THIS MORNING...AND AS THE DAY PROGRESSES AND THE COLD AIR ADVECTIVE PATTERN STRENGTHENS...THE STRATOCUMULUS DECK SHOULD ERODE AND CLOUD COVER WILL DECREASE WITH SOME AREAS BECOME MOSTLY SUNNY LATE IN THE AFTERNOON. STILL SOME PATCHES OF DENSE FOG ARE PERSISTING EARLY THIS MORNING...BUT ISSUES SHOULD DIMINISH AS THE MORNING PROGRESSES. NO PRECIPITATION IS EXPECTED WITH THE BOUNDARY...BUT A FEW SPRINKLES OR LOCAL DRIZZLE CANNOT BE RULED COMPLETELY OUT THIS MORNING. MODELS ARE DEVELOPING A WEAK TO MODERATE OFFSHORE EVENT OVER THE NEXT COUPLE DAYS AS HIGH PRESSURE ESTABLISHES ON THE BACKSIDE OF THE CYCLONIC FLOW PATTERN. SURFACE GRADIENTS WILL START TRENDING OFFSHORE THIS AFTERNOON...WITH THE STRONGEST TRENDS ESTABLISHING BETWEEN KSBA-KSMX AND KBFL-KLAX. MODELS CONTINUE TO TAKE A MARGINAL STANCE FOR A WIND ADVISORY FOR TONIGHT. WHILE MODELS GENERATE A FAIR AMOUNT WINDS IN THE BOUNDARY LAYER AND AT 950 MB...THERE IS LITTLE UPPER-LEVEL SUPPORT BEYOND THE FIRST 2500 FEET OFF THE SURFACE. SURFACE GRADIENTS REMAIN BELOW TYPICAL ADVISORY LEVELS...AND 950 MB AND 850 MB THERMAL GRADIENTS ARE MARGINAL. WITH MORE FACTORS WEIGHING HEAVILY AGAINST ADVISORY LEVEL WINDS TONIGHT...FORECAST MENTIONS SUB-ADVISORY WINDS THROUGH THE I-5 CORRIDOR AND ACROSS SOUTHERN SANTA BARBARA COUNTY AND THE NEXT SHIFT CAN REVISIT THE WIND SCENARIO. WITH OFFSHORE FLOW ESTABLISHING...A WARMING AND DRYING TREND WILL ESTABLISH ON SUNDAY. MODEL 950 AND 850 MB TEMPERATURES WARM SLIGHTLY AND MIXING RATIOS CRASH ON SUNDAY. MODELS CONTINUE TO SUGGEST THE WARMEST DAY WILL BE MONDAY...WITH NAM-WRF 950 MB TEMPERATURES AND GFS 850 MB TEMPERATURES PEAKING ON MONDAY. HOWEVER...A CLOSER LOOK AT THE SURFACE PATTERN WOULD SUGGEST THAT TUESDAY COULD BE JUST AS WARM AS MONDAY. MUCH WILL DEPEND ON HOW A DEVELOPING TROUGH EVOLVES OVER THE WEEKEND. .LONG TERM (TUESDAY-FRIDAY)...MODELS CONTINUE TO DEVELOP AND DIG A TROUGH OVER THE EASTERN PACIFIC FOR MIDWEEK...BUT MODELS STILL DIFFER IN THE EVOLUTION OF THE TROUGHS DEVELOPMENT. GFS SEEMS TO BE THE LEAST PROGRESSIVE WITH THE DEVELOPMENT OF THE TROUGH...WHILE THE GEM CONTINUE TO BE THE MOST AGGRESSIVE. IT IS WAY TOO EARLY TO GET AN IDEA ON HOW STRONG THE TROUGH WILL BE BASED UPON THE LACK OF AGREEMENT IN THE MODELS CURRENTLY. WITH INSPECTION OF THE THREE MODELS HANDLING OF THE WINDS IN THE GULF OF ALASKA...HIGHER CONFIDENCE SHOULD BE PLACED WITH THE GEM AND ECMWF FOR A SLIGHTLY LATER ARRIVAL AND FURTHER SOUTHERLY COLD PUSH. && .MARINE...VERY LARGE NW SWELL...GENERATED BY A MONSTROUS STORM IN THE GULF OF ALASKA...HAS BEGUN TO SPREAD INTO THE OUTER WATERS EARLY THIS MORNING...WITH 20 FT SEAS ALREADY AFFECTING THE CAPE SAN MARTIN BUOY TO THE W OF PT PIEDRAS BLANCAS. SWELL AND SEAS WILL CONTINUE TO BUILD...WITH COMBINED SEAS LIKELY REACHING 18 TO 23 FEET ACROSS THE OUTER WATERS TODAY. SWELL PERIODS WILL BE IN THE 15 TO 17 SECOND RANGE. THIS LARGE AND MODERATELY LONG PERIOD NW SWELL WILL GENERATE HIGH SURF ON W AND NW FACING BEACHES OF SLO AND SBA COUNTIES THIS WEEKEND...AND HIGH SURF ADVISORIES ARE IN EFFECT. VERY HIGH SEAS WILL SLOWLY SUBSIDE SUNDAY NIGHT AND MONDAY. DUE TO THE NWLY DIRECTION OF THE SWELL...THE BULK OF ITS ENERGY WILL BE CONFINED PRIMARILY TO THE OUTER WATERS. HOWEVER...SINCE THE SWELL PERIOD IS REASONABLY LONG...SOME SWELL ENERGY WILL REFRACT AROUND PT CONCEPTION AND INTO THE INNER WATERS. SWELL OR COMBINED SEAS COULD REACH 10 FEET ACROSS THE FAR WESTERN SECTIONS OF THE SANTA BARBARA CHANNEL AND ACROSS THE INNER WATERS NW OF SANTA CATALINA ISLAND LATER TODAY THROUGH SUNDAY. ABOVE NORMAL SURF WILL LIKELY DEVELOP ON EXPOSED WEST FACING BEACHES OF VENTURA AND LOS ANGELES COUNTIES TODAY AND CONTINUE THROUGH SUNDAY. DEPENDING UPON HOW MUCH ENERGY SPREADS THROUGH THE CHANNEL...HIGH SURF ADVISORIES MAY HAVE TO BE EXPANDED TO COASTAL SECTIONS OF VENTURA AND LOS ANGELES COUNTIES. && .AVIATION...07/1155Z...STRATUS WAS BEGINNING TO GET MORE ORGANIZED EARLY THIS MORNING. S OF PT CONCEPTION...IFR CIGS WERE THE RULE IN COASTAL AREAS WITH MVFR VSBYS...WHILE N OF PT CONCEPTION CIGS WERE GENERALLY IN THE LIFR CATEGORY. EXPECT THE VALLEYS TO REMAIN CLEAR THIS MORNING...AT LEAST WITH ABOUT 80 PERCENT CONFIDENCE. THE WRF SHOWS A FAIR AMOUNT OF MOISTURE LINGERING IN COASTAL SECTIONS OF L.A. COUNTY...SO BURN OFF TIMES MAY BE SLOWER THAN EXPECTED. KLAX...LOW CONFIDENCE IN TAF. EXPECT SOLID IFR CIGS TO PUSH INTO THE AIRFIELD BY 12Z OR 13Z. THERE IS A 30 PERCENT CHANCE THAT CIGS WILL LINGER AS LATE AS 21 OR 22Z. KBUR...MODERATE TO HIGH CONFIDENCE IN TAF. THERE IS A 20 PERCENT CHANCE THAT IFR CIGS WILL PUSH INTO THE AIRPORT BETWEEN 13Z AND 16Z. && .LOX WATCHES/WARNINGS/ADVISORIES... HIGH SURF ADVISORY (SEE LAXCFWLOX). SMALL CRAFT ADVISORY (SEE LAXMWWLOX). COASTAL FLOOD STATEMENT (SEE LAXCFWLOX). MARINE WEATHER STATEMENT (SEE LAXMWSLOX). && $$ SYNOPSIS/PUBLIC...HALL AVIATION/MARINE...DB WWW.WEATHER.GOV/LOSANGELES