Small Craft Advisory 102, NWS Los Angeles, CA

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1100 PM PDT TUE SEP 18 2012

NEW AVIATION DISCUSSION

.SYNOPSIS...

HIGH PRESSURE ALOFT AND WEAK ONSHORE FLOW WILL RESULT IN A
WARMING TREND THROUGH THURSDAY OR FRIDAY. AN APPROACHING LOW
PRESSURE SYSTEM WILL THEN PRODUCE A GRADUAL COOLING TREND INTO
EARLY NEXT WEEK. NIGHT THROUGH MORNING LOW CLOUDS AND FOG ARE
EXPECTED FOR PORTIONS OF THE COAST THROUGH SATURDAY...THEN THE
MARINE LAYER CLOUDS WILL LIKELY EXPAND THROUGH EARLY NEXT WEEK.

&&

.UPDATE...

RIDGING AND SUBSIDENCE ALOFT WILL CONTINUE TO PRODUCE A WARMING
TREND. ONSHORE FLOW WILL CONTINUE TO WEAKEN OVER THE COMING DAYS
AND THE MARINE LAYER WILL CONTINUE TO THIN. CURRENT KLAX AMDAR
SOUNDINGS INDICATE A MARINE LAYER DEPTH NEAR 700 FEET THIS
EVENING...ABOUT 300 FEET THINNER THAN LAST NIGHT. MARINE LAYER
STRATUS COVERAGE WILL BE PROBLEMATIC OVER THE COMING DAYS SOUTH OF
POINT CONCEPTION...ESPECIALLY WITH SHALLOW OCEAN WATER
TEMPERATURES IN THE MID 60S TO LOWER 70S. THE FOG COVERAGE WAS
SCALED BACK SLIGHTLY FOR TONIGHT AND INTO WEDNESDAY MORNING.

THE LATEST MODEL SOLUTIONS INDICATE 950 MB TEMPERATURES
WARMING EACH DAY THROUGH FRIDAY...WITH 1000-500 MB THICKNESS
VALUES CLIMBING THROUGH THURSDAY. A FEW MINOR TWEAKS WERE MADE TO
TEMPERATURES FOR WEDNESDAY...BRINGING THE WARMEST LOCATIONS OF
THE SAN FERNANDO AND SANTA CLARITA VALLEYS JUST TO THE CENTURY
MARK.

MAIN CONCERN FOR THE SHORT-TERM IS THE DEVELOPING SUNDOWNER WINDS
ON WEDNESDAY EVENING. KSBA-KSMX SURFACE GRADIENTS HAVE TIGHTENED
NICELY THIS EVENING...AND WINDS WERE INCREASED SLIGHTLY IN THE
UPDATE FOR TONIGHT. KSBA-KSMX SURFACE GRADIENTS ARE PROGGED BY
THE MODELS TO TIGHTEN A BIT MORE ON WEDNESDAY EVENING...AND 950
MB THERMAL GRADIENTS ARE NEAR THRESHOLDS FOR AN ADVISORY LEVEL
EVENT ON WEDNESDAY EVENING. WITH MUCH TIME FOR MORE DATA TO
ARRIVE...ANY DECISIONS WILL BE TABLED FOR NOW TO GET A BIT MORE
CONFIDENCE.

&&

.PREV DISCUSSION...

LONG TERM...BY SATURDAY ALL MODELS GENERALLY AGREE THAT THE
EASTERN PACIFIC LOW WILL BE SOMEWHERE OVER/NEAR THE NORTHERN
CALIFORNIA COAST. THE GFS KEEPS THE LOW CENTER FURTHER NORTH THAN
THE ECMWF AND ESPECIALLY THE GEM...AND THIS TREND IS CONTINUED
THROUGH THE WEEKEND. BY SUNDAY ALL MODELS BEGIN TO SHIFT THE LOW
INLAND THROUGH EITHER CENTRAL OR NORTHERN CALIFORNIA...AND OVER
NEVADA BY MONDAY. ALL MODELS HINT AT THE POSSIBILITY OF SOME
PRECIPITATION FORMING IN THE VICINITY OF THE LOW...BUT CONSIDERING
THAT HEIGHTS OVER SW CALIFORNIA REMAIN NEAR/ABOVE 582 MB...PREFER
TO SEE BETTER MODEL AGREEMENT BEFORE COMMITTING TO ANYTHING MORE
THAN A COOLING TREND AND PARTLY CLOUDY SKIES. THE LOWERING HEIGHTS
ALOFT WILL ALSO PRODUCE A DEEPENING MARINE LAYER...WITH OVERNIGHT
LOW CLOUDS ADVANCING INTO THE VALLEYS EACH NIGHT THROUGH THE LONG
TERM.

&&

.AVIATION...

19/0600Z

GOOD CONFIDENCE IN COASTAL TAFS AND VERY GOOD CONFIDENCE IN INLAND
TAFS. THERE IS A 30 PERCENT CHANCE OF MVFR VIS RESTRICTIONS FROM
12Z-16Z AT THE COASTAL TERMINALS AND A 30 PERCENT CHANCE OF IFR CIGS
FROM KOXR TO KLGB.

KLAX...GOOD CONFIDENCE IN TAF. THERE IS A 30 PERCENT CHC OF IFR CIGS
FORM 13Z-17Z.

KBUR...HIGH CONFIDENCE IN TAF.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).
GALE WATCH (SEE LAXMWWLOX).

&&

PUBLIC...HALL/SMITH
AVIATION...ASR
SYNOPSIS...SUKUP

WWW.WEATHER.GOV/LOSANGELES

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
923 PM PDT TUE SEP 18 2012

CAZ034>041-044>046-051>054-059-087-088-547-548-191300-
SAN LUIS OBISPO COUNTY CENTRAL COAST-
SANTA BARBARA COUNTY CENTRAL COAST-SANTA YNEZ VALLEY-
SAN LUIS OBISPO COUNTY INTERIOR VALLEYS-CUYAMA VALLEY-
SANTA BARBARA COUNTY SOUTH COAST-VENTURA COUNTY COAST-
LOS ANGELES COUNTY COAST INCLUDING DOWNTOWN LOS ANGELES-
VENTURA COUNTY INTERIOR VALLEYS-VENTURA COUNTY COASTAL VALLEYS-
SANTA MONICA MOUNTAINS RECREATIONAL AREA-
SAN LUIS OBISPO COUNTY MOUNTAINS-
SANTA BARBARA COUNTY MOUNTAINS-VENTURA COUNTY MOUNTAINS-
LOS ANGELES COUNTY MOUNTAINS EXCLUDING THE SANTA MONICA RANGE-
ANTELOPE VALLEY-CATALINA ISLAND-SANTA CLARITA VALLEY-
LOS ANGELES COUNTY SAN FERNANDO VALLEY-
LOS ANGELES COUNTY SAN GABRIEL VALLEY-
923 PM PDT TUE SEP 18 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHWESTERN CALIFORNIA.

.DAY ONE... TONIGHT

PATCHY DENSE FOG WILL AFFECT PORTIONS OF THE VENTURA AND LOSANGELES
COUNTY COASTAL AREAS LATE TONIGHT...WITH VISIBILITIES OF ONE QUARTER
MILE OR LESS POSSIBLE.

.DAYS TWO THROUGH SEVEN... WEDNESDAY THROUGH MONDAY

THROUGH WEDNESDAY MID MORNING...PATCHY DENSE FOG WILL AFFECT
PORTIONS OF THE VENTURA AND LOS ANGELES COUNTY COASTAL AREAS...WITH
VISIBILITIES OF ONE QUARTER MILE OR LESS POSSIBLE. STRONG WINDS WILL
DEVELOP ACROSS THE OUTER COASTAL WATERS BETWEEN WEDNESDAY AFTERNOON
AND WEDNESDAY NIGHT...WITH GALE FORCE WINDS POSSIBLE.

* GALE WATCH...............SEE WHUS76 KLOX - MWWLOX FOR DETAILS *

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

HALL