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000
FXUS66 KLOX 191733
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1032 AM PDT SUN MAY 19 2013

.SYNOPSIS...
GUSTY NORTH WINDS ARE POSSIBLE THROUGH MONDAY MORNING FOR THE
MOUNTAIN AREAS. WARMING IS EXPECTED THROUGH MONDAY AS A RIDGE OF
HIGH PRESSURE BUILDS AND WEAK OFFSHORE FLOW DEVELOPS. AN INCREASE IN
NIGHT THROUGH MORNING LOW CLOUDS AND FOG...ALONG WITH A COOLING
TREND...IS THEN EXPECTED TUESDAY AND BEYOND AS LOW PRESSURE TO THE
NORTH INCREASES ONSHORE FLOW. COOL WEATHER AND PARTLY TO MOSTLY
CLOUDY CONDITIONS WILL LIKELY CONTINUE INTO NEXT WEEKEND.

&&

.SHORT TERM (TODAY-TUE)...
GUSTY NORTH WINDS CONTINUE OVER THE INTERIOR MOUNTAINS OF LA AND
VENTURA COUNTIES...AND THE ANTELOPE VALLEY THIS MORNING. THE WINDS
ARE BECOMING MORE ISOLATED TO THE MORE FAVORED PEAKS AND ARE
EXPECTED TO SUBSIDE BELOW ADVISORY LEVEL BY LATE THIS MORNING. A
VERY SHALLOW MARINE LAYER NORTH OF POINT CONCEPTION PRODUCED PATCHY
LOW CEILINGS OVER THE NORTHERN SANTA BARBARA COUNTY...BUT THIS IS
DISSIPATING RAPIDLY AND MAINLY CLEAR SKIES WILL PREVAIL THROUGH THE
REMAINDER OF THE DAY. FURTHER SOUTH THE MARINE LAYER IS LIFTING AND
SCATTERED CLOUDS REMAIN OVER THE EASTERN LA BASIN AND SAN GABRIEL
VALLEY. BY EARLY THIS AFTERNOON EXPECT ALL AREAS TO BE SUNNY.

HEIGHTS ALOFT WILL RISE TODAY AS A RIDGE OVER THE EASTERN PACIFIC
SHIFTS TOWARD THE COAST. THIS IN COMBINATION WITH CONTINUED ONSHORE
FLOW WILL PRODUCE A FEW DEGREES OF WARMING TODAY COMPARED TO
YESTERDAY. COASTAL AREAS WILL BE IN THE LOWER TO MID 70S WITH INLAND
HIGHS IN THE MID TO UPPER 80S.

.FROM PREVIOUS DISCUSSION...
RESPECTABLE OFFSHORE FLOW DEVELOPS TONIGHT AND THE ONLY LOW CLOUDS
WILL BE NEAR LONG BEACH WHICH IS WELL SHELTERED FROM THE OFFSHORE
FLOW. OFFSHORE FLOW AND 584DM HGTS WILL COMBINE TO MAKE MONDAY THE
WARMEST DAY OF THE NEXT 7 WITH MAX TEMPS 4 TO 8 DEGREES ABOVE NORMAL.

THE FLOW SWITCHES TO ONSHORE MONDAY NIGHT AND AN EDDY SPINS UP WHICH
WILL CREATE A FAIRLY EXTENSIVE CLOUD DECK. HGTS ARE FAIRLY HIGH AND
THIS SHOULD KEEP THE LOW CLOUDS SMOOSHED OUT OF THE VLYS.

THE LOW CLOUDS WILL LAST UNTIL MID MORNING AND THEN SKIES WILL BE
SUNNY. MAX TEMPS WILL FALL TO NEAR NORMAL.

.LONG TERM (WED-SAT)...
NO CHANGE IN LONG TERM THINKING THROUGH THURSDAY AS A COLD UPPER LOW
SETS UP SHOP OVER OREGON AND SPINS. THE RESULTANT CYCLONIC
FLOW...LOWERING HGTS...AND ONSHORE FLOW WILL CREATE A DEEP VLY
PENETRATING MARINE CLOUD LAYER THAT WILL LIKELY STRUGGLE TO CLEAR
THE BEACHES. MAX TEMPS WILL BE BLO NORMAL.

MDLS DISAGREE ON WHAT WILL BECOME OF THE UPPER LOW FRIDAY AND SAT
BUT ALL AGREE THAT THERE WILL BE SOME SORT OF TROF OVER THE WEST
COAST. DO NOT THINK THERE WILL BE MUCH CHANGE TO THE FORECAST AND
THE NIGHT THROUGH MORNING LOW CLOUDS WILL CONTINUE AS WILL THE BELOW
NORMAL MAX TEMPS.

&&

.AVIATION...19/1800Z.

MID/UPPER LEVEL RIDGE OF HIGH PRESSURE UPSTREAM WILL BUILD OVER THE
AREA. UPPER LEVEL MODERATE NORTHWEST WINDS AND MID LEVEL LIGHT
NORTH WINDS WILL PREVAIL OVER THE AREA. LOW LEVEL CLOUD TOPS
APPROXIMATELY 2.6KFT THIS MORNING WILL DIFFER BY MINUS 2KFT MONDAY
MORNING. MIXED WEAK TO MODERATE ONSHORE AND NORTHERLY PRESSURE
GRADIENT THROUGH 20/11Z THEN WEAK OFFSHORE GRADIENT BETWEEN
20/11-20/18Z AND WEAK TO MODERATE ONSHORE THEREAFTER.

KLAX...CHANCE VSBY 5SM HZ BETWEEN 20/12-12/17Z. OTHERWISE CURRENT
SKY/VSBY CONDITIONS LIKELY.

KBUR...CURRENT SKY/VSBY CONDITIONS VERY LIKELY THROUGH PERIOD.

VIRTUALLY CERTAIN - 95-100%
VERY LIKELY       - 80-95%
LIKELY            - 60-80%
CHANCE            - 30-60%
VERY UNLIKELY     - 20% OR LESS

&&

.FIRE WEATHER...

GUSTY NORTHWEST WINDS WITH WARMING TEMPERATURES AND LOWERING
HUMIDITIES WILL BRING ELEVATED FIRE DANGER THROUGH THIS EVENING
ACROSS THE MOUNTAINS...ANTELOPE VALLEY...SANTA CLARITA...AND SBA
SOUTH COAST. WIND GUSTS WILL GENERALLY BE IN THE 30 TO 40 MPH RANGE
ACROSS THESE AREAS TODAY...WITH THE WINDS AFFECTING THE SBA SOUTH
COAST THIS EVENING. HUMIDITIES WILL FALL TO AROUND 10 PERCENT ACROSS
THE MOUNTAINS...ANTELOPE VALLEY...AND SANTA CLARITA VALLEY TODAY.

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 ONLY MINOR 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 POSSIBLE.
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.

&&

.MARINE...A THERMAL TROUGH OF LOW PRESSURE WILL INTENSIFY NEAR SHORE
WHILE HIGH PRESSURE PERSISTS OVER THE EASTERN PACIFIC THOUGH EARLY
MONDAY. AND A GALE WARNING IS IN EFFECT OVER THE OUTER WATERS FROM
SAN CLEMENTE ISLAND TO POINT PIEDRAS BLANCAS AND INCLUDING THE INNER
WATERS FROM POINT PIEDRAS BLANCAS TO POINT SAL THROUGH LATE TONIGHT.
THE RIDGE OF HIGH PRESSURE OVER THE EASTERN PACIFIC WILL WEAKEN
MONDAY. A TROUGH OF LOW PRESSURE IS THEN EXPECTED TO MOVE SOUTHEAST
OVER THE OFFSHORE AND COASTAL WATERS EARLY TUESDAY THROUGH EARLY
WEDNESDAY WHILE A RIDGE OF HIGH PRESSURE STRENGTHENS OVER THE
EASTERN PACIFIC. NORTHWEST WINDS WILL LIKELY TO INCREASE NEAR SHORE
NORTH OF POINT CONCEPTION AND OVER THE OUTER WATERS SOUTH OF POINT
CONCEPTION TUESDAY EVENING THROUGH WEDNESDAY. A GALE WATCH MAY BE
ISSUED EARLY THIS WEEK AND WHEN THE RISK OF GALE FORCE WINDS HAS
SIGNIFICANTLY INCREASED.

&&

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

&&

$$

PUBLIC...RORKE/SMITH
FIRE...GOMBERG
SYNOPSIS...SUKUP

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