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000
FXUS66 KLOX 201139 AAA
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
440 AM PDT MON MAY 20 2013

UPDATED AVIATION SECTION

.SYNOPSIS...

GUSTY NORTH WINDS AND WARMING TEMPERATURES ARE EXPECTED TODAY AS
WEAK OFFSHORE FLOW DEVELOPS. A COOLING TREND WILL BEGIN ON TUESDAY
ALONG WITH AN INCREASE IN NIGHT THROUGH MORNING LOW CLOUDS AND FOG
AND WILL WILL LIKELY CONTINUE INTO NEXT WEEKEND.

&&

.SHORT TERM (TODAY-THU)...
MARINE LAYER IS 1400 FEET DEEP AND A WEAK EDDY IS SPINNING UP SOME
MARINE STRATUS INTO SOUTHERN L.A. COUNTY AND CATALINA ISLAND. AT THE
SAME TIME A COOL SFC HIGH WILL BUILD INTO NEVADA AND CREATE AN
OFFSHORE FLOW PATTERN BY MID MORNING. THIS OFFSHORE PUSH WILL HALT
THE PROGRESS OF THE LOW CLOUDS. IT WILL ALSO BE JUST STRONG ENOUGH
TO PRODUCE A BRIEF BURST OF WIND ADVISORY GUSTS IN THE MOUNTAINS AND
THE SANTA CLARITA VLY...ALTHOUGH THE SANTA CLARITA VLY WILL BE RIGHT
ON THE EDGE OF ADVISORY CRITERIA. THE OFFSHORE FLOW WILL THEN ALLOW
FOR A NICE WARM UP ACROSS THE AREA ESP ACROSS THE COASTS. THE
CENTRAL COAST WILL RISE 8 TO 12 DEGREES ABOVE NORMAL AND OTHER
COASTAL AREAS WILL BE 4 TO 8 DEGREES ABOVE NORMAL.

A FEW DAYS AGO TUESDAY LOOKED LIKE IT WAS GOING TO CLOUDIER AND MUCH
COOLER THAN TODAY...BUT IT LOOKS LIKE THE COOLING WILL BE DELAYED AS
THE RIDGE LINGERS INTO TUESDAY. THERE WILL ONLY BE MINIMAL MARINE
LAYER CLOUDS...MOSTLY ACROSS THE LA AND VTA COASTS AND WHILE MAX
TEMPS WILL COOL THEY WILL STILL BELOW NORMAL.

SYNOPTICALLY NOTHING HAS CHANGED MUCH FROM PREVIOUS THINKING. A BIG
COOL UPPER LOW WILL MOVE INTO THE PAC NW AND THEN SLIDE DOWN INTO
OREGON. ONSHORE FLOW AND AN EDDY WILL DEVELOP OVER THIS AREA. BUT
NEW NAM SHOWS THAT THE MARINE LAYER WILL BE MORE RELUCTANT TO FORM
ESP ACROSS THE SBA SOUTH COAST WHERE WEAK SUNDOWNERS WILL KEEP THE
CLOUDS PUSHED AWAY. DIALED THE CLOUD COVERAGE BACK A LITTLE DURING
THIS PERIOD. MAX TEMPS SHOULD STILL FALL AND WILL BE A FEW DEGREES
BLO NORMAL.

.LONG TERM (FRI-SUN)...
ALL MDLS AGREE THAT THE UPPER LOW WILL CONTINUE TO SPIN OVER THE PAC
NW DURING THE XTND PERIOD. THE RELENTLESS ONSHORE FLOW AND CYCLONIC
TURNING SHOULD BE ENOUGH CREATE A DEEP AND EXTENSIVE MARINE LAYER
THAT WILL HAVE TROUBLE CLEARING THE BEACHES IN THE AFTERNOON. MAX
TEMPS WILL REMAIN BELOW NORMAL THROUGH THE PERIOD.

&&

.AVIATION...20/1140Z
EXPECT VFR CONDITIONS THROUGH THIS EVENING...EXCEPT FOR PATCHY IFR
CIGS THROUGH MID MORNING ACROSS PORTIONS OF THE CENTRAL COAST...THE
SANTA YNEZ VALLEY AND THE L.A. COUNTY COAST. EXPECT SOMEWHAT MORE
WIDESPREAD IFR CONDS IN COASTAL SECTIONS TONIGHT/EARLY TUE.

KLAX...LOW TO MODERATE CONFIDENCE IN 12Z TAF. THERE IS A 40 PERCENT
THAT IFR CONDS WILL NOT MATERIALIZE THIS MORNING.

KBUR...VERY HIGH CONFIDENCE IN 12Z TAF WITH VFR CONDS THRU THE
PERIOD.

&&

.FIRE WEATHER...

(FROM PREVIOUS DISCUSSION)

GUSTY NORTHWEST TO NORTH WINDS WILL CONTINUE TO BRING LOWERING
HUMIDITIES AND ELEVATED FIRE DANGER THROUGH THIS EVENING ACROSS THE
MOUNTAINS...ANTELOPE VALLEY...SANTA CLARITA VALLEY...AND SBA SOUTH
COAST. THESE AREAS WILL GENERALLY SEE GUSTS IN THE 30 TO 40 MPH
RANGE. ALREADY SEEING HUMIDITIES LOWERING TO AROUND 10 PERCENT THIS
AFTERNOON ACROSS THE SANTA CLARITA VALLEY...ALONG WITH TEMPERATURES
CLIMBING INTO THE LOWER 90S.

BY LATE TONIGHT AND MONDAY...SURFACE HIGH PRESSURE BUILDS INTO THE
GREAT BASIN...SETTING THE STAGE FOR A BRIEF OFFSHORE WIND EVENT FOR
THE REGION. THE PROJECTED LAX-DAGGETT GRADIENT IS ONLY EXPECTED TO BE
AROUND -1.5 MB...WITH SOME UPPER LEVEL WIND SUPPORT. OFFSHORE
WINDS ARE EXPECTED TO DEVELOP ACROSS THE MOUNTAINS LATE
TONIGHT...THEN DESCEND INTO THE VALLEYS ON MONDAY MORNING. AT THIS
TIME...WIND GUSTS IN THE 35 TO 40 MPH RANGE CAN BE EXPECTED IN THE
MOUNTAINS ON MONDAY MORNING...WITH GUSTS IN THE 25 TO 35 MPH RANGE
ACROSS THE VALLEYS (MAINLY SANTA CLARITA AND EASTERN VENTURA
VALLEYS). THERE WILL LIKELY BE WIDESPREAD HUMIDITIES BETWEEN 10 AND
15 PERCENT ON MONDAY ACROSS THE MOUNTAINS AND VALLEYS OF LOS ANGELES
AND VENTURA COUNTIES...WITH ISOLATED SINGLE DIGIT READINGS LIKELY.
WHILE THIS OFFSHORE WIND EVENT DOES NOT APPEAR TO BE STRONG ENOUGH OR
HAVE SUFFICIENT DURATION TO WARRANT A RED FLAG WARNING...THERE WILL
BE ELEVATED FIRE DANGER ACROSS THE MOUNTAINS AND VALLEYS ON
MONDAY...ESPECIALLY CONSIDERING THE VERY DRY FUELS FOR THIS TIME OF
YEAR. THE OFFSHORE WINDS ARE EXPECTED TO DIMINISH FAIRLY RAPIDLY ON
MONDAY AFTERNOON...WITH ONSHORE WINDS GRADUALLY SPREADING ACROSS
COASTAL AND VALLEY AREAS THROUGH THE AFTERNOON AND EVENING HOURS.

&&

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

&&

$$

PUBLIC...RORKE
AVIATION..DB
SYNOPSIS...KJ

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