000 
FXUS66 KLOX 292030
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
130 PM PDT FRI MAY 29 2009

NEW AVIATION DISCUSSION

.SHORT TERM...OVERALL...TODAY IS SHAPING UP TO BE VERY SIMILAR TO 
THURSDAY. MID-LEVEL FLOW ON SOUNDINGS AND MODELS CONTINUES TO BE 
SOUTHEASTERLY THIS MORNING AND AFTERNOON. SO...MID-LEVEL MOISTURE
WILL LIKELY CONTINUE ACROSS THE AREA THROUGH THE EVENING...RESULTING
IN ANOTHER ROUND OF AFTERNOON CONVECTION. AT THIS TIME...THE 
NORTHERN SECTIONS OF VTU/SBA COUNTIES AND SOUTHERN SLO COUNTY LOOK
VULNERABLE TODAY. IN ADDITION...IT APPEARS THE MOISTURE AND 
INSTABILITY WILL BE BETTER OVER LAX COUNTY THIS AFTERNOON...SO 
WILL EXPECT BIT MORE CONVECTIVE DEVELOPMENT OVER THE MOUNTAINS AND 
POTENTIALLY THE ANTELOPE VALLEY. RADAR WILL BE WATCHED VERY CLOSELY 
TODAY AS THE POTENTIAL FOR WARNING-LEVEL STORMS IS PRESENT.

OTHERWISE...EXPECT A TYPICAL MARINE LAYER DAY FOR THE COASTS AND 
COASTAL VALLEYS. CURRENT AMDAR SOUNDINGS INDICATE MARINE INVERSION
AROUND 2500 FEET WITH STRATUS IN THE SANTA CLARITA VALLEY. EXPECT
A VERY SIMILAR BURNOFF AS THURSDAY...WITH SOME CLOUDS LIKELY TO
LINGER ALONG THE COAST THROUGH THE AFTERNOON. 

OVERALL...CURRENT ZONES LOOK GOOD AND NO UPDATES ARE PLANNED. NOW
JUST WAIT AND SEE WHAT HAPPENS THIS AFTERNOON WITH THE CONVECTION.

*** LONG TERM FROM PREVIOUS DISCUSSION ***

.LONG TERM (MONDAY-THURSDAY)...MODELS ARE STARTING TO DIVERGE ON
THE DEVELOPMENT OF A TROUGH OVER THE EASTERN PACIFIC. AS INDICATED
IN EARLIER DISCUSSIONS...THE MOVEMENT REMAINS UNPREDICTABLE FROM
RUN-TO-RUN DUE TO THE TROUGH BEING CUTOFF FROM THE FLOW PATTERN.
THE LATEST ECMWF SOLUTION HAS SWITCHED POSITIONS WITH THE GFS FROM
THIS TIME LAST NIGHT...BECOMING LESS PROGRESSIVE IN NATURE WITH
THE STORM SYSTEM. FOR THE CURRENT TIME...AN ONSHORE FLOW REGIME
WILL PERSIST THROUGH THE LONG TERM PERIOD. THE TROUGH WILL LIKELY
BRING FURTHER COOLING AND THE PACKAGE TRENDS THAT WAY WITH PARTLY
CLOUDY SKIES. LOW CONFIDENCE SHOULD STILL BE PLACED IN THE TIMING
AND EXACT MOVEMENT OF THE SYSTEM AT THIS TIME. THE PACKAGE HAS
INTRODUCED POPS AND MENTION OF WEATHER FOR AREAS NORTH OF POINT
CONCEPTION DUE THE AGREEMENT IN TIME OF THE SOME INGREDIENTS AMONG
THE GFS AND ECMWF SOLUTIONS. HOWEVER...A SLOWING OF THE SYSTEM
WOULD NOT BE SURPRISING.

&&

.AVIATION...29/2030Z.
A TALE OF TWO ATMOSPHERES...THE BOUNDARY LAYER IS MIRED IN STRATUS 
AS A RESULT OF THE MARINE LAYER...AND ABOVE THE MARINE LAYER THE MID 
LEVELS OF THE ATMOSPHERE ARE QUITE UNSTABLE WITH THUNDERSTORMS 
DEVELOPING OVER THE ANTELOPE VALLEY. IN ALL...IT IS A COMPLEX 
FORECAST WITH DECREASING CONFIDENCE IN THE EVOLUTION. ANY 
THUNDERSTORMS HAVE THE POTENTIAL TO RELEASE AN OUTFLOW BOUNDARY 
WHICH COULD EASILY DISPERSE THE MARINE LAYER AT A MOMENTS NOTICE. 
SINCE THE VALLEY TAFS ARE CLOSEST TO THUNDERSTORM ACTIVITY...KBUR 
AND KVNY COULD BECOME FREE OF THE LOW STRATUS IN THE NEXT COUPLE OF 
HOURS DUE TO NEARBY CONVECTION. THE COASTAL TAFS...ON THE OTHER 
HAND...HAVE THE POTENTIAL TO STAY MIRED IN LOW CLOUDS AND FOG ALL 
DAY UNLESS THERE IS WIDESPREAD THUNDERSTORM ACTIVITY THAT SPREADS 
INTO THE COASTAL SECTIONS. FOR NOW...WILL EXPECT THE COASTAL 
SECTIONS TO REMAIN UNAFFECTED BY THUNDERSTORM ACTIVITY. 

KLAX...MVFR CONDITIONS WITH CEILINGS LASTING THROUGH THE DAY. THERE 
IS A 20 PERCENT CHANCE OF CLEARING THIS AFTERNOON. THEN...LOW CLOUDS 
SHOULD BECOME REESTABLISHED OVER THE AIRFIELD EARLY THIS EVENING AND 
CONTINUE INTO SATURDAY MORNING. 

KBUR...MVFR CONDITIONS WITH CEILINGS LASTING THROUGH THE DAY. THERE 
IS A 50 PERCENT CHANCE OF CLEARING THIS AFTERNOON...AND A 20 PERCENT 
CHANCE OF A GLANCING BLOW FROM A NEARBY THUNDERSTORM THIS AFTERNOON. 
THEN...LOW CLOUDS SHOULD BECOME REESTABLISHED OVER THE AIRFIELD 
LATER THIS EVENING AND CONTINUE INTO SATURDAY MORNING WITH MVFR TO 
LOCAL IFR CONDITIONS.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
NONE

&&

$$

PUBLIC...THOMPSON
AVIATION...SWEET

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