000
FXUS66 KLOX 230555
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
955 PM PST SUN NOV 22 2009

...NEW AVIATION DISCUSSION...

.SYNOPSIS...OFFSHORE FLOW ESTABLISHING BENEATH UPPER-LEVEL HIGH
PRESSURE WILL BRING A WARMING AND DRYING TREND THROUGH LATE WEEK.
A MODERATE TO STRONG OFFSHORE GRADIENT DEVELOPING WILL INCREASE
WINDS ACROSS THE AREA...ESPECIALLY THROUGH AND BELOW PASSES AND
CANYONS. A COOLING TREND SHOULD DEVELOP NEXT WEEKEND AS LOW
PRESSURE APPROACHES THE AREA.

&&

.UPDATE...A STRONG NORTHERLY SURFACE GRADIENT EVIDENCED BY
PRESSURE GRADIENTS BETWEEN KLAX-KSFO...KLAX-KBFL...AND KBFL- KSBA
IS CURRENTLY DEVELOPING AS EXPECTED. STRONG WINDS HAVE DEVELOPED
THROUGH THE INTERSTATE 5 CORRIDOR THIS EVENING OVER THE SANTA YNEZ
RANGE THIS EVENING...AND WITH GRADIENTS STILL TIGHTENING...THESE
WINDS WILL LIKELY ONLY STRENGTHEN FURTHER. LATEST UPDATE TO THE
WIND ADVISORY ADDED SOME VALLEY AREAS TO ADVISORY AREAS AND
INCREASED SPEEDS THROUGH THE MOUNTAINS. MODEL ARE DIVERGING SOME
ON HOW STRONG THE WINDS WILL BE TONIGHT. GOOD AGREEMENT DOES EXIST
BETWEEN ALL MODEL SOLUTIONS THAT THE SURFACE GRADIENT WILL SHIFT
FROM NORTHERLY THIS EVENING TO NORTHEASTERLY AFTER MIDNIGHT.
HOWEVER...THE NAM-WRF IS STRUGGLING IN HANDLING SOME THE SYNOPTIC
SCALE FEATURES THIS EVENING...ESPECIALLY WITH DEVELOPING AN AREA
OF SUBSIDENCE BEHIND A WEAK VORTICITY MAXIMUM CURRENTLY PUSHING
OVER THE AREA. GFS SEEMS TO HAVE A BETTER HANDLE ON THIS FEATURE.
AS A RESULT MORE EMPHASIS SHOULD BE PLACED ON THE 13-KM RUC AND
00Z GFS SOLUTIONS. WHILE A MORE COARSE SOLUTION...GFS MODEL
INSPECTION REVEALS 20 KNOTS OF WINDS WITH A 6 DEGREE THERMAL
GRADIENTS BETWEEN THE MOJAVE DESERT AND THE COASTAL PLAIN. 13-KM
RUC SOLUTION INDICATE 30 TO 40 KNOTS DEVELOPING TONIGHT IN THE
BOUNDARY LAYER LATER TONIGHT...BUT 850 MB WINDS ARE AROUND 30
KNOTS.

MAIN CONCERN WITH THE PACKAGE IS THE POOR HANDLING OF SOME OF THE
FINER DETAILS WITH THE DEVELOPING OFFSHORE FLOW PATTERN. WINDS
WILL HAVE TO BE CLOSELY MONITORED THROUGHOUT TONIGHT BECAUSE
THERE IS SOME POSSIBILITY THAT WINDS COULD EXCEED ADVISORY
CRITERIA. FOR THE CURRENT TIME...PRODUCTS SEEMS REASONABLE FOR
THE MODEL PERFORMANCE. AN UPDATE WILL BE PERFORMED LATER TO WARM
TEMPERATURES SLIGHTLY FOR SOME LOCATION AFFECTED BY OFFSHORE
FLOW.

&&

.PREV DISCUSSION... /ISSUED 400 PM PST SUN NOV 22 2009/ 

SHORT TERM...THE EVENT WILL STRENGTHEN FURTHER INTO THE
WEEK...WITH WINDS INCREASING THROUGH WEDNESDAY. THERE IS A CHANCE
THAT THE EVENT COULD BECOME MODERATE TO LOCALLY STRONG BY
WEDNESDAY. NAM-WRF AND GFS 850 MB THERMAL AND SURFACE GRADIENTS
TIGHTEN BETWEEN THE THE ANTELOPE VALLEY AND THE LOS ANGELES COUNTY
COAST. 850MB WINDS ALSO INCREASE FROM 25 TO 30 KNOTS AT 850 MB ON
MONDAY NIGHT AND TUESDAY MORNING...TO 30 T0 35 KNOTS AT 850 MB BY
TUESDAY NIGHT AND WEDNESDAY. THE SITUATION HAS CAUSE FOR CONCERN
AND CLOSE MONITORING BY FUTURE SHIFTS AS A POTENTIAL EXISTS FOR
DAMAGING WINDS TO DEVELOP. IN ADDITION...THIS COULD ALSO CAUSE
FIRE WEATHER CONDITIONS TO DETERIORATE OVER THE AREA.

LONG TERM...MODELS ARE STARTING TO COME INTO AGREEMENT THAT
OFFSHORE FLOW WILL WEAKEN ON THURSDAY...AND A TROUGH WILL APPROACH
THE WEST COAST ON THURSDAY NIGHT OR FRIDAY. WHILE MODELS VARY IN
STRENGTH AND INTENSITY OF THE TROUGH FROM RUN-TO-RUN...ALL MODEL
SOLUTIONS SEEM TO INDICATE THE BEST CHANCES FOR PRECIPITATION...IF
ANY...OCCURRING NORTH OF POINT CONCEPTION LATE NEXT WEEK.
OTHERWISE...COOLER TEMPERATURES AND SLIGHTLY MORE MOIST CONDITIONS
WILL LIKELY RESULT. SKY COVER WAS INCREASED AND SOME MARINE LAYER
WAS ADDED TO THE PACKAGE FOR LATE WEEK.

&&

.AVIATION...

23/0545Z.

NORTH WINDS WILL TURN NORTHEAST OVERNIGHT. LOW CLOUDS WILL SPILL 
INTO THE INTERIOR VLYS OF SLO AND SBA COUNTIES. KVNY AND KSBA WILL 
HAVE ERRATIC WINDS OVERNIGHT WITH BRIEF BURSTS OF NORTH WINDS TO 25 
KT POSSIBLE. SKIES WILL BE CLEAR FOR THE COAST AND VLY SITES EXCEPT 
KSMX. LGT TURBC OVER THE MTNS.

KLAX...GOOD CONFIDENCE IN TAF. A 20 PERCENT CHANCE OF MVFR VIS 
12Z-17Z.

KBUR...VERY GOOD CONFIDENCE IN CIG/VIS FORECAST. WINDS WILL BE 
ERRATIC OVERNIGHT AND DURING THE MORNING WITH CALM...EAST 4-8KT AND 
NORTH WINDS 8 TO 12 KT ALL EQUALLY POSSIBLE. A 20 PERCENT CHANCE OF 
NORTH WINDS 15 TO 20 KT. LGT TURBC SFC-070 MONDAY MORNING AND 
AFTERNOON.


&&

.LOX WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY (SEE LAXNPWLOX). 
SMALL CRAFT ADVISORY (SEE LAXMWWLOX). 
GALE WARNING (SEE LAXMWWLOX). 
COASTAL FLOOD STATEMENT (SEE LAXCFWLOX).

&&

$$

PUBLIC...HALL
AVIATION...RORKE
SYNOPSIS...TH

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