FXUS66 KLOX 100328
AFDLOX
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
828 PM PDT SAT MAY 9 2009
.UPDATE...AN ONSHORE FLOW PATTERN PROVIDED BY LOW-LEVEL NORTHWEST
FLOW WILL REMAIN IN PLACE THROUGH THE WEEKEND. CURRENTLY...THE
MARINE LAYER DEPTH REMAINS AROUND 2000 FEET THIS EVENING FROM
LATEST KLAX ACARS SOUNDING...WHILE THINNING NORTH OF POINT
CONCEPTION. SOUTH OF POINT CONCEPTION...A WELL-DEVELOPED EDDY
CIRCULATION WILL CONTINUE TO BRING LOW CLOUDS AND FOG INTO THE
VALLEYS TONIGHT AND SUNDAY. DEPENDING ON HOW STRONG THE DEVELOPING
GRADIENT GETS ACROSS THE I-5 CORRIDOR...THERE IS A CHANCE THAT LOW
CLOUDS AND FOG COULD MAKE IT INTO THE SANTA CLARITA VALLEY LATE
TONIGHT OR SUNDAY MORNING. IF WINDS GET STRONG ENOUGH...THE EDDY
CIRCULATION COULD NOT HAVE ENOUGH STRENGTH TO PUSH STRATUS INTO THE
SANTA CLARITA VALLEY. FOR NOW...THE NEXT SHIFT WILL BE BRIEFED
ABOUT THE POSSIBILITY...BUT WITH DEEPENING NOT TAKING PLACE UNTIL
AFTER 2 AM TONIGHT...THE MARINE LAYER DEPTH WILL HAVE TO BE
WATCHED CLOSELY.
WITH THE LATEST NAM-WRF SOLUTION INDICATING WINDS MAY APPROACH
ADVISORY STRENGTH TONIGHT THROUGH THE I-5 CORRIDOR...SOME CONCERN
EXISTS THAT AN ADVISORY MAY BE NEEDED. WITH LOW CONFIDENCE DUE TO
THE GRADIENT TRENDS AND WITH THE NAM BUFR DATA INDICATING A
DEEPENING MARINE LAYER TONIGHT...WINDS COULD LOCALLY REACH
ADVISORY CRITERIA IN MORE FAVORABLE LOCATION SUCH AS WHITAKER
PEAK...BUT WIDESPREAD STRONG WINDS SHOULD NOT BE EXPECTED.
A COOLING TREND WILL PERSIST THROUGH THE WEEKEND BEFORE A WEAK
BOUNDARY DROPS SOUTH IN THE NORTHWEST LOW-LEVEL FLOW ON MONDAY.
&&
.PREV DISCUSSION... /ISSUED 145 PM PDT SAT MAY 9 2009/
SHORT TERM...THE PATTERN IS EXPECTED TO CHANGE LATE SUNDAY INTO
MONDAY AS STRONGER NORTHWEST FLOW SPREADS OVER THE ENTIRE AREA,
PUSHING THE EDDY CIRCULATION SOUTH. IF THIS HAPPENS LIKE THE NAM
IS DEPICTING (AND IT DID A GOOD JOB WITH THIS EARLIER THIS WEEK),
THEN WE CAN EXPECT NORTHWEST WINDS TO INCREASE OVER THE SBA FIRE
AREA AS EARLY AS SUNDAY NIGHT AND CERTAINLY BY MONDAY AFTERNOON.
WINDS WILL ALSO PICK UP ACROSS THE MOUNTAINS (POSSIBLY TO ADVISORY
LEVELS) AND ALSO FILTER DOWN INTO THE VALLEYS BY MONDAY EVENING.
IN ADDITION TO THE WIND INCREASE, WE CAN EXPECT DAYTIME HIGHS TO
JUMP UP 5 TO 8 DEGREES MONDAY AND TUESDAY ACROSS COAST AND VALLEY
AREAS S OF PT CONCEPTION. LOW CLOUDS WILL BE PUSHED SOUTH WITH THE
EDDY CIRCULATION BUT SOME CLOUDS MAY LINGER ACROSS SRN LA COUNTY
DURING THE NIGHT AND MORNING HOURS.
LONG TERM...NOT A WHOLE LOT OF CHANGE AT LEAST THROUGH THURSDAY.
WEAK TO MODERATE NORTHERLY FLOW WILL CONTINUE, KEEPING MARINE LYR
TO A MINIMUM AND DAYTIME HIGHS 5 TO 10 DEGREES ABOVE NORMAL MOST
AREAS. BY LATE IN THE WEEK AND EARLY NEXT WEEKEND MODELS DO SHOW
NORTHERLY FLOW WEAKENING AS HIGH PRESSURE TO OUR NORTH BREAKS
DOWN, PERHAPS RETURNING TO MORE OF A TYPICAL ONSHORE FLOW. THIS
WILL RESULT IN COOLER TEMPS MOST AREAS WITH A GRADUAL RETURN OF
THE MARINE LYR.
AVIATION...10/0052Z.
SOUTH OF POINT CONCEPTION...MVFR TO VFR CONDITIONS WILL BECOME 
PREDOMINANTLY IFR TO MVFR BETWEEN 04Z AND 10Z TONIGHT. AROUND 
12Z...CONDITIONS WILL IMPROVE TO THE MVFR CATEGORY AS CEILINGS LIFT. 
COASTAL TERMINALS WILL LIKELY STRUGGLE TO CLEAR AGAIN ON 
SUNDAY...WITH CLEARING NOT OCCURRING BETWEEN 20Z AND 23Z SUNDAY.
NORTH OF POINT CONCEPTION...VFR CONDITIONS WILL LIKELY PERSIST AT 
MOST TERMINALS...EXCEPT IFR CONDITIONS WILL DEVELOP AT KSMX BETWEEN 
05Z AND 08Z TONIGHT. THERE IS A CHANCE THAT IFR CONDITIONS MAY ALSO 
IMPACT KSBP AFTER 06Z TONIGHT.
 
KLAX...THERE IS A 40 PERCENT CHANCE OF SCATTERING OUT BETWEEN NOW 
AND 03Z THIS EVENING...OTHERWISE MVFR CONDITIONS WILL LIKELY PERSIST 
THROUGHOUT THE PERIOD. THERE IS A 20 PERCENT CHANCE THAT CEILINGS 
COULD LIFT INTO THE VFR CATEGORY AFTER 13Z ON SUNDAY MORNING. KLAX 
WILL LIKELY STRUGGLE TO CLEAR ON SUNDAY...WITH CLEARING POSSIBLY 
OCCURRING BETWEEN 20Z AND 23Z SUNDAY.
KBUR...VFR CONDITIONS WILL PERSIST THROUGH AT LEAST 08Z...WITH IFR 
TO MVFR CONDITIONS SPREADING INLAND TO KBUR BETWEEN 08Z AND 12Z 
TONIGHT. VFR CONDITIONS SHOULD REDEVELOP BETWEEN 16Z AND 18 SUNDAY.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
GALE WARNING (SEE LAXMWWLOX).
&&
$$
HALL/WOFFORD
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