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000
FXUS66 KLOX 191709
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1005 AM PDT WED JUN 19 2013

.SYNOPSIS...

A WEAK TROUGH OF LOW PRESSURE ALOFT TO THE NORTH OF THE STATE WILL
CONTINUE TO PRODUCE A NORTHERLY PRESSURE DIFFERENCE ACROSS THE
STATE THROUGH THURSDAY. GUSTY WINDS WILL CONTINUE ACROSS PORTIONS
OF SOUTHWEST CALIFORNIA THROUGH LATE TONIGHT. ONSHORE FLOW AND A
COOLING TREND SHOULD DEVELOP FOR LATE WEEK AND INTO THE WEEKEND.
A WARMING TREND COULD DEVELOP NEXT WEEK AS UPPER-LEVEL HIGH
PRESSURE BUILDS WEST.

&&

.SHORT TERM (TODAY-FRIDAY)...
NO NEED FOR A MORNING UPDATE. CURRENT HIGHLIGHTS INCLUDE WIND
ADVISORIES FOR THE MOUNTAINS...ANTELOPE VALLEY...CENTRAL COAST AND
THE SOUTH COAST OF SANTA BARBARA COUNTY. THE NEXT UPDATE ON THE
ADVISORIES IS DUE EARLY THIS AFTERNOON AND THERE MAY BE A NEED TO
EXTEND THE ADVISORY FOR THE LA/VENTURA COUNTY MOUNTAINS UNTIL 3 AM
THURSDAY TO ACCOUNT FOR THE DIURNALLY FAVORABLE TIME FOR GUSTY WINDS
THROUGH THE I-5 CORRIDOR. OTHERWISE...THE OTHER AREAS COVERED BY AN
ADVISORY LOOK GOOD IN TERMS OF EXPIRATION TIMES. ANOTHER HIGHLIGHT
OF SIGNIFICANCE IS THE RED FLAG WARNING IN EFFECT FOR THE MOUNTAINS
AND SOUTH COAST OF SANTA BARBARA COUNTY DUE TO AN EXTENDED PERIOD OF
GUSTY WINDS AND LOW HUMIDITIES...CAUSING CONCERNS FOR HIGH FIRE
DANGER.

TODAY LOOKS LIKE THE LAST DAY OF STRONG GUSTY NORTH WINDS AS THE
MODEL DATA SUGGESTS THAT THE NORTHERLY GRADIENTS WILL RELAX OVER THE
NEXT 24 HOURS IN DEFERENCE TO GREATER ONSHORE FLOW. THIS TRANSITION
IS BEING CAUSED BY A GRADUAL WEAKENING OF THE WEST COAST TROUGH AND
THE RESULTANT SURGES OF HIGH PRESSURE DROPPING IN FROM THE NORTH.
STILL...NORTH WINDS ARE EXPECTED TO CONTINUE FOR THE NEXT 24 TO 36
HOURS...ESPECIALLY IN THE COASTAL  WATERS AND FAVORED MOUNTAIN
PASSES. EDDY DEVELOPMENT IN THE SOUTHERN COASTAL WATERS BECOMES A
BIT MORE PRONOUNCED FOR THE NEXT COUPLE OF MORNINGS AND THIS MAY
RESULT IN GREATER LOW CLOUD COVERAGE IN SOUTH COASTAL SECTIONS FOR
THURSDAY AND FRIDAY MORNINGS.

TEMPERATURES IN THE COASTAL AND VALLEY AREAS ARE EXPECTED TO
GRADUALLY COOL OVER THE NEXT TWO DAYS...ALTHOUGH THE CENTRAL COAST
MAY SEE LITTLE CHANGE IN HIGH TEMPERATURES IF THE LOW CLOUDS AND FOG
ARE SLOW TO RETURN UP THERE. AS THE TROUGH ALONG THE WEST COAST
WEAKENS OVER THE NEXT 48 HOURS...HIGH TEMPERATURES INLAND MAY
ACTUALLY RISE A BIT FOR THE REMAINDER OF THE WEEK DUE TO RISING
HEIGHTS AND THICKNESSES.

***FROM PREVIOUS DISCUSSION***

.LONG TERM (SATURDAY-TUESDAY)...

A DEEPER MARINE LAYER AND ANOTHER WEAK DISTURBANCE BRUSHING THE
AREA SHOULD ALLOW FOR ONSHORE FLOW TO INCREASE AND BRING A COOLING
TREND THROUGH THE WEEKEND. MARINE LAYER COVERAGE WAS EXPANDED OVER
THE PREVIOUS PACKAGE AND THE MIXED LAYER COOLED.

GFS MODEL TRENDS SUGGEST A WARMING TREND DEVELOPING FOR THE
MIDDLE OF NEXT WEEK...AND IF OPERATIONAL GFS SOLUTIONS VERIFY...A
SUMMER WEATHER PATTERN WILL TAKE HOLD OVER THE AREA FOR LATE NEXT
WEEK. TEMPERATURES HAVE BEEN WARMED IN THE PACKAGE...BUT IF THE
MODEL TRENDS CONTINUE...TEMPERATURES MAY HAVE BE WARMED FURTHER
THAN THE CURRENT FORECAST.

&&

.AVIATION...19/0500Z.

HIGH CONFIDENCE WITH 12Z TAF PACKAGE. VFR CONDITIONS WILL PERSIST AT
MOST TERMINALS EXCEPT FOR 20 PERCENT CHANCE FOR IFR CONDS AT KSMX
THROUGH 16Z. 20 PERCENT CHANCE THAT MVFR CIGS WILL NOT MATERIALIZE
AT LAX BETWEEN 12Z AND 15Z THIS MORNING. HIGH CONFIDENCE FOR VFR
CONDS FOR ALL SITES...EXCEPT 30 PERCENT CHANCE FOR MVFR VSBYS FOR
COASTAL SITES TONIGHT AFTER 06Z.

KLAX...VFR CONDITIONS WILL PERSIST THROUGH 10Z THURSDAY. WITH 30
PERCENT CHANCE FOR MVFR CONDS AFTER THAT THROUGH 17Z.

KBUR...VFR CONDITIONS ARE EXPECTED THROUGHOUT THE PERIOD.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING (SEE LAXRFWLOX).
GALE WARNING (SEE LAXMWWLOX).
WIND ADVISORY (SEE LAXNPWLOX).
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).
HIGH RIP CURRENT RISK (SEE LAXSRFLOX).

&&

$$

PUBLIC...SWEET/HALL
AVIATION...CK
SYNOPSIS...HALL

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