Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 210420
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
820 PM PST THU NOV 20 2014

.SYNOPSIS...

A COOL AND UNSETTLED WEATHER PATTERN WILL CONTINUE ACROSS SOUTHWEST
CALIFORNIA INTO THE WEEKEND AS A SERIES OF WEAK LOW PRESSURE SYSTEMS
MOVE OVER THE REGION. OFFSHORE FLOW BENEATH HIGH PRESSURE ALOFT WILL
BRING A WARMING AND DRYING TREND NEXT WEEK.

&&

.SHORT TERM (TONIGHT-SUN)...A RATHER SHARP UPPER LEVEL TROF WAS
MOVING INTO CENTRAL CA THIS EVENING. A COLD FRONT ASSOCIATED WITH
THE UPPER TROF WAS BRINGING SCATTERED MAINLY LIGHT SHOWERS TO
WESTERN SLO/SBA COUNTIES WITH A FEW HUNDREDTHS OF AN INCH REPORTED
AT A FEW STATIONS THRU EARLY THIS EVENING. THE UPPER TROF WILL PUSH
QUICKLY INLAND AND SE ACROSS CENTRAL AND SRN CA TONIGHT. AT THE SAME
TIME...THE SURFACE COLD FRONT WILL DISSIPATE WHILE MOVING THRU THE
FORECAST AREA. THE CHANCES OF SHOWERS WILL SPREAD INTO L.A./VTU
COUNTIES OVERNIGHT...WITH SHOWERS BECOMING LIKELY ON THE N MTN
SLOPES. RAINFALL AMOUNTS OVERNIGHT WILL BE LIGHT...GENERALLY 0.15
INCH OR LESS. MUCH OF THE COAST AND VLYS OF VTU/L.A. COUNTIES WILL
PROBABLY HAVE TRACE AMOUNTS OF PCPN. THIS WEATHER SYSTEM WILL HAVE
COLD AIR ALOFT (-22 DEG C AT 500 MB) AND GOOD INSTABILITY OVERNIGHT
(LI`S -4 TO -5 ACCORDING TO THE NAM)...WITH THE SLIM POSSIBILITY OF
AN ISOLATED LIGHTNING STRIKE ESPECIALLY IN THE MTNS. HOWEVER...THE
CHANCES OF ANY THUNDERSTORM DEVELOPMENT ARE ONLY ABOUT 10 PERCENT.
FOR NOW...WILL KEEP ANY MENTION OF THUNDER OUT OF THE ZONES FOR
TONIGHT.

THE UPPER TROF WILL CONTINUE TO MOVE OFF THE TO SE THRU FRI...
WITH 500 MB HEIGHTS RECOVERING OVER THE FORECAST AREA. A BROAD
NORTHERLY LOWER LEVEL FLOW WILL DEVELOP OVER THE AREA ON FRI...WHICH
SHOULD DIMINISH CLOUD COVER FOR THE COAST AND VLYS...AND KEEP
CLOUDINESS ALONG THE N MTNS SLOPES AND INTERIOR SLO/SBA COUNTIES. A
FEW MORE SHOWERS WILL ALSO BE POSSIBLE ON THE N SLOPES IN THE
MORNING...MAINLY FOR VTU COUNTY. TEMPS WILL BE ON THE COOL SIDE
AGAIN WITH HIGHS A FEW DEGREES BELOW NORMAL FOR MOST AREAS.

UPPER LEVEL RIDGING IS EXPECTED TO PREVAIL OVER SWRN CA FRI NIGHT
AND SAT. A BROAD NW FLOW ALOFT WITH AN UPPER RIDGE WELL OFF THE CA
COAST CAN BE EXPECTED SAT NIGHT AND SUN. A WEAK UPPER LEVEL
DISTURBANCE IS FORECAST TO MOVE INTO SLO/SBA COUNTIES SAT WITH A
SLIGHT CHANCE TO CHANCE OF SHOWERS...THEN THE SLIGHT CHANCE OF
SHOWERS WILL SPREAD INTO THE N MTN SLOPES FOR SAT NIGHT. THIS WILL
BE ANOTHER WEATHER SYSTEM WITH SCATTERED LIGHT AMOUNTS OF PCPN.
GUSTY NW TO N WINDS ARE EXPECTED FOR THE L.A./VTU MTNS FRI NIGHT AS
WELL AS THE SBA COUNTY MTNS AND S COAST. THESE WINDS WILL CONTINUE
AT TIMES THRU SAT NIGHT...AND SPREAD INTO THE ANTELOPE VLY. WIND
GUSTS TO NEAR ADVISORY LEVELS ARE POSSIBLE. THE FLOW IS EXPECTED TO
TURN MORE NORTHEAST ON SUN WITH GUSTY WINDS BELOW AND THRU THE
FAVORED PASSES AND CANYONS. THERE SHOULD BE MOSTLY CLOUDY SKIES FOR
SLO/SBA COUNTIES AND THE N MTN SLOPES OF VTU COUNTY FRI NIGHT INTO
SAT EVENING...WITH PARTLY CLOUDY SKIES ELSEWHERE. CLEARING SKIES
SHOULD THEN DEVELOP OVER THE FORECAST AREA ON SUN THANKS TO THE
DRYING OFFSHORE FLOW. TEMPS ON SAT WILL REMAIN SLIGHTLY BELOW
NORMAL...THEN TURN MILDER AND CLOSER TO NORMAL MAINLY W OF THE MTNS
ON SUN...WHILE TEMPS CONTINUE SLIGHTLY BELOW NORMAL FOR THE MTNS AND
DESERTS.

***FROM PREVIOUS DISCUSSION***

.LONG TERM (MON-THU)...FAIRLY HIGH CONFIDENCE IN THE MODEL
CONSISTENCY THROUGH WEDNESDAY BUT THEN THE ECM TAKES ITS OWN PATH
WITH A DIGGING TROUGH OVER THE GREAT BASIN LATE IN THE WEEK. OTHER
MODEL SOLUTIONS (GFS/GEM) PUSH A RIDGE TO OUR EAST WITH SOUTHWEST
FLOW ALOFT DEVELOPING BY THURSDAY IN ADVANCE OF A LARGER EASTERN
PACIFIC STORM SYSTEM. FOLLOWING THE PLACEMENT OF THE RIDGE ON THE
GFS WILL EXPECT INCREASING OFFSHORE FLOW AND WARMER/DRIER WEATHER
MONDAY THROUGH WEDNESDAY. SOME MODERATION IN TEMPERATURES AND A
POTENTIAL RETURN TO ONSHORE FLOW WOULD BE PLAUSIBLE BY THURSDAY.
READINGS IN THE UPPER 70S AND 80S WILL BE LIKELY FOR THE COASTS AND
VALLEYS OF VENTURA AND LOS ANGELES COUNTIES TUESDAY AND WEDNESDAY.
&&

.AVIATION...21/0030Z.

AT 0010Z OVER KLAX...THE BASE OF THE INVERSION WAS AT 5600 FEET AND
THE TOP OF THE INVERSION WAS LOCATED AT 6500 FEET WITH A TEMPERATURE
OF 10C.

MODERATE CONFIDENCE IN THE 00Z TAFS N OF POINT CONCEPTION...WITH
MVFR/IFR CIGS POSSIBLE THRU LATE TONIGHT OR SAT MORNING...ALTHO THE
TIMING OF THE LOW CLOUDS BETWEEN FLIGHT CATS IS PROBLEMATIC AND MAY
BE OFF ONE TO TWO HOURS. FOR THE COAST AND VLYS S OF POINT
CONCEPTION...MODERATE CONFIDENCE IN THE 00Z TAFS DUE TO
UNCERTAINTIES OF MVFR CIGS AND THE TIMING AND EXTENT OF THESE CIGS.
THE TIMING OF THE LOW CLOUDS MAY BE OFF PLUS/MINUS AN HOUR OR
TWO...AND MVFR CIGS MAY BE INTERMITTENT AT TIMES. IT DOES LOOK LIKE
THE LOW CLOUDS WILL CLEAR OUT OF THE REGION BY EARLY FRI MORNING AS
NORTHERLY OFFSHORE FLOW DEVELOPS. FOR KWJF AND KPMD...MODERATE
CONFIDENCE DUE TO UNCERTAINTIES WITH REGARDS TO MVFR CIGS DEVELOPING
TONIGHT BETWEEN 06Z AND 14Z. THERE IS A 20 PERCENT CHANCE THEY MAY
NOT DEVELOP...AND THE TIMING OF THE LOW CLOUDS MAY BE OFF PLUS/MINUS
AN HOUR OR SO. OTHERWISE...VFR CONDITIONS ARE EXPECTED AT KWJF AND
KPMD THRU FRI AFTERNOON.

KLAX AND KBUR...MODERATE CONFIDENCE IN 00Z TAF. THERE ARE
UNCERTAINTIES WITH MVFR CIGS AND THE TIMING AND EXTENT OF THESE
CIGS. THE TIMING OF THE LOW CLOUDS MAY BE OFF PLUS/MINUS AN HOUR OR
TWO...AND MVFR CIGS MAY BE INTERMITTENT AT TIMES. THE LOW CLOUDS
SHOULD CLEAR TO VFR BY 14Z FRI AS A NORTHERLY FLOW DEVELOPS.

&&

.MARINE...20/800 PM PST...

OUTER WATERS...HIGH CONFIDENCE IN MODERATE NW WINDS WITH SCA
CONDITIONS ACROSS THE TWO SOUTHERN OUTER ZONES TONIGHT. THIS
ADVISORY WILL LIKELY BE EXTENDED THRU THE WEEKEND. MODELS SHOW THE
WINDS INCREASING SAT INTO SUN WITH GUSTS NEAR 30 KT NEAR SAN NICOLAS
IS. AND PT CONCEPTION...WITH A CHANCE OF 35 KT GUSTS BY SUN NIGHT.

INNER WATERS...MODERATE TO HIGH CONFIDENCE THAT NW WINDS TO SCA
LEVELS WILL AFFECT THE WESTERN PORTION OF PZZ650 AND 655 THRU LATE
TONIGHT. GUSTS TO 25 KNOTS ARE EXPECTED OVER THESE AREAS ALONG WITH
BUILDING WIND WAVES.

A RELATIVELY LONG PERIOD WEST SWELL WILL DIMINISH AS A SIMILAR
PERIOD NW SWELL MOVES INTO THE WATERS ON FRI. A SOMEWHAT LARGER NW
SWELL AROUND 10 FEET AT 15 SECONDS WILL MOVE INTO THE OUTER WATERS
SAT NIGHT INTO SUN.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).
HIGH RIP CURRENT RISK (SEE LAXSRFLOX).

&&

$$

PUBLIC...SIRARD/BOLDT
AVIATION...SIRARD
MARINE...SMITH/SIRARD
SYNOPSIS...BOLDT

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