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SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 
210 PM PDT THU SEP 3 2015

...MARINE DISCUSSION UPDATED...

.SYNOPSIS...

MODERATE ONSHORE FLOW WILL GRADUALLY WEAKEN LABOR DAY WEEKEND AS AN 
UPPER LEVEL LOW DEPARTS TO THE EAST. AS A RESULT...A SLOW BUT STEADY 
WARMING TREND WILL BEGIN...WITH ABOVE NORMAL TEMPERATURES EXPECTED 
BY NEXT FRIDAY. MORNING CLOUDS EXTENDING INTO THE VALLEYS FRIDAY 
WILL RETREAT TO SOME COASTAL LOCATIONS BY EARLY NEXT WEEK.

&& 

.SHORT TERM (TONIGHT-SUN)...OVERALL...12Z MODELS IN GOOD SYNOPTIC 
AGREEMENT THROUGH THE PERIOD. AT UPPER LEVELS...LOW WILL MOVE INTO 
THE PACIFIC NORTHWEST TONIGHT/FRIDAY...MOVE SOUTH INTO NORTHERN 
CALIFORNIA ON SATURDAY...THEN INLAND INTO THE NORTHERN GREAT BASIN 
ON SUNDAY. NEAR THE SURFACE...MODERATE ONSHORE FLOW WILL PREVAIL 
THROUGH SATURDAY...THEN TURN WEAKLY OFFSHORE ON SUNDAY.

FORECAST-WISE...NOTHING TOO EXCITING EXPECTED FOR THE AREA THROUGH 
THE WEEKEND. CLOUD WISE...THERE DOES NOT APPEAR TO BE ANY NOTICEABLE 
MOISTURE MOVING AROUND THE UPPER LOW...SO DO NOT ANTICIPATE MUCH OF 
ANY MID/HIGH LEVEL CLOUDS. HOWEVER...THE MARINE LAYER STRATUS WILL 
REMAIN A CHALLENGE. WITH CONTINUED ONSHORE FLOW AND LOWERING H5 
HEIGHTS THROUGH FRIDAY...MARINE INVERSION WILL REMAIN RATHER DEEP 
AND STRATUS SHOULD PUSH INTO THE LOWER COASTAL SLOPES. FOR FRIDAY 
NIGHT AND SATURDAY...H5 HEIGHTS INCREASE A BIT AND ONSHORE GRADIENTS 
WEAKEN SLIGHTLY...SO ANTICIPATE LESS WIDESPREAD STRATUS COVERAGE 
ACROSS THE AREA. BY SATURDAY NIGHT/SUNDAY...WEAK OFFSHORE FLOW 
SHOULD KEEP MOST AREAS STRATUS-FREE...WITH THE ONLY EXCEPTION 
POTENTIALLY THE LA COAST AND SAN GABRIEL VALLEY WHERE SOME 
STRATUS/FOG COULD DEVELOP. 

AS FOR WINDS...MODERATE ONSHORE WINDS ARE EXPECTED THROUGH SATURDAY. 
THE WINDS WILL BECOME GUSTY EACH AFTERNOON/EVENING ACROSS THE 
MOUNTAINS AND DESERTS...BUT SHOULD REMAIN BELOW ADVISORY LEVELS. FOR 
SATURDAY NIGHT/SUNDAY...THE SURFACE GRADIENTS TURN WEAKLY OFFSHORE 
BUT UPPER LEVEL SUPPORT IS MINIMAL. SO...THERE WILL BE SOME LOCAL 
NORTHEAST WINDS IN THE USUAL PLACES...BUT BELOW ADVISORY LEVELS.

AS FOR TEMPERATURES...FRIDAY WILL BE THE COOLEST DAY IN THE SHORT 
TERM. ON SATURDAY...TEMPERATURES WILL REBOUND A BIT WITH LESS MARINE 
INFLUENCE AND WEAKER ONSHORE GRADIENTS. FOR SUNDAY...EXPECT A VERY 
NOTICEABLE TEMPERATURE JUMP DUE TO WEAK OFFSHORE FLOW. MOST AREAS 
AWAY FROM THE COAST SHOULD BE IN THE MID 80S TO MID 90S ON SUNDAY. 

.LONG TERM (MON-THU)...OVERALL...12Z MODELS CONTINUE TO BE IN DECENT 
AGREEMENT THROUGH THE PERIOD. AT UPPER LEVELS...WEAK TROUGH WILL 
LINGER OVER THE AREA MONDAY/TUESDAY...THEN A RIDGE WILL TRY TO MOVE 
IN FROM THE SOUTHEAST WEDNESDAY/THURSDAY. NEAR THE SURFACE...IT 
LOOKS LIKE WEAK DIURNAL FLOW WILL PREVAIL...WEAKLY OFFSHORE AT NIGHT 
AND ONSHORE DURING THE DAY.

FORECAST-WISE...THE EXCITEMENT LEVELS WILL CONTINUE TO BE MINIMAL. 
MONDAY/TUESDAY SHOULD SEE A GRADUAL RETURN OF THE MARINE LAYER 
STRATUS AND A GRADUAL COOLING TREND. FOR WEDNESDAY/THURSDAY...THE 
MARINE INVERSION WILL LIKELY SHRINK A BIT AND REMAIN CONFINED 
GENERALLY TO THE COASTAL PLAIN. WITH THE LESS MARINE INFLUENCE...THE
TEMPERATURES ON WEDNESDAY/THURSDAY SHOULD EXHIBIT A WARMING TREND.

&&

.AVIATION...03/18Z.

AT 17Z AT KLAX... THE INVERSION WAS ABOUT 3000 FEET DEEP.  THE TOP 
WAS NEAR 6350 FEET WITH A TEMPERATURE OF 17 DEGREES CELSIUS.

OVERALL... MODERATE CONFIDENCE IN THE 18Z TAFS ALONG THE COAST AND 
IN ADJACENT VALLEYS AND HIGH CONFIDENCE ELSEWHERE.  CIGS CONTINUE AT 
A FEW LOCATIONS BUT ALL TAF SITES WILL BE VFR BY 20Z.  MARINE CLOUDS 
RETURN TONIGHT AS EARLY AS 03Z IN SOME COASTAL LOCATIONS AND AS LATE 
AS 14Z AT KPRB BUT ALL COASTAL AND ADJACENT VALLEY LOCATIONS WILL 
HAVE A RETURN OF LIFR/IFR CIGS AT CENTRAL COAST SITES AND PRIMARILY 
MVFR CIGS AT THE OTHERS WITH A SIMILAR CLEARING PATTERN TOMORROW AS 
TODAY.  OTHERWISE AND ELSEWHERE VFR CONDITIONS WILL PREVAIL.

LAX... MODERATE TO HIGH CONFIDENCE IN THE 18Z TAF.  CIGS CONTINUE 
ATTM BUT SHOULD GO VFR 18Z-20Z.  MARINE CLOUDS RETURN TONIGHT AROUND 
05Z WITH MVFR CIGS FOR KLAX.  A SIMILAR CLEARING PATTERN TOMORROW AS 
TODAY.  OTHERWISE VFR CONDITIONS WILL PREVAIL.

BUR... MODERATE CONFIDENCE IN THE 18Z TAF.  CIGS CONTINUE ATTM BUT 
SHOULD GO VFR 18Z-20Z.  MARINE CLOUDS RETURN TONIGHT AROUND 06Z WITH 
MVFR CIGS FOR KBUR.  A SIMILAR CLEARING PATTERN TOMORROW AS TODAY.   
OTHERWISE VFR CONDITIONS WILL PREVAIL.

&&

.MARINE...03/200 PM. 

GOOD CONFIDENCE IN SMALL CRAFT ADVISORY CONDITIONS DEVELOPING THIS 
AFTERNOON AND CONTINUING THROUGH LATE TONIGHT ACROSS THE NORTHERN 
TWO THIRDS OF THE OUTER WATERS. THERE IS A TWENTY FIVE PERCENT 
CHANCE THAT A SMALL CRAFT ADVISORY WILL BE NEEDED FOR THE INNER 
WATERS AS WELL.

SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED AGAIN ACROSS THE ENTIRE 
OUTER WATERS FRIDAY AFTERNOON THROUGH SATURDAY NIGHT. THERE IS A 
THIRTY FIVE PERCENT CHANCE THAT AN ADVISORY WILL BE NEEDED FOR THE 
NORTHERN INNER WATERS DURING THAT PERIOD AS WELL.

MEANWHILE... STORM FORCE WINDS IN THE SOUTH PACIFIC GENERATED A 
SWELL THAT WILL AFFECT THE COASTAL WATERS OF SOUTHWEST CALIFORNIA 
OVER THE WEEKEND.  SWELL HEIGHTS WILL BE 2 TO 4 FEET WITH INTERVALS 
NEAR 20 SECONDS.  MARINERS SHOULD BE PREPARED FOR LONG PERIOD SWELLS 
THAT WILL LIKELY HAVE EXTRA SURGING AND CURRENTS.  SHOALING IS 
LIKELY IN SHALLOWER WATER AND IN SOME HARBOR ENTRANCES.  

.BEACHES...A LONG PERIOD SOUTH SWELL WILL LIKELY BRING ELEVATED SURF 
TO SOUTH AND SOUTHWEST FACING BEACHES OVER THE HOLIDAY WEEKEND... 
WITH A RATHER HIGH RISK OF DANGEROUS RIP CURRENTS EXPECTED. 

&&

.LOX WATCHES/WARNINGS/ADVISORIES... 
BEACH HAZARD STATEMENT (SEE LAXCFWLOX).
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).

&&
$$

PUBLIC...RAT
AVIATION..KJ
MARINE/BEACHES...KJ
SYNOPSIS...RM

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