Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 202159
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
200 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)...MAIN FORECAST IMPACTS WILL BE SCATTERED
SHOWERS TONIGHT AND WINDS ON SATURDAY. UPPER LOW IS JUST NORTH OF
SFO BAY AND CONTINUES TO GENERATE LIGHTNING IN THE COLDER AIR ALOFT
OFF THE COAST. RADAR ONLY PICKING UP VIRGA ALONG THE CENTRAL COAST
AT 130PM AND NOT EXPECTING MORE ORGANIZED RAIN UNTIL MAINLY AFTER
00Z IN SLO COUNTY. MID AND HIGH CLOUDS HAVE BEEN RAPIDLY SPREADING
ACROSS SOUTHWEST CA TODAY KEEPING OUR HIGH TEMPERATURES A GOOD 3-7
DEGREES COOLER THAN YESTERDAY.

LOW PRESSURE TRACKS SOUTHEASTWARD ACROSS THE SOUTHERN SAN JOAQUIN
VALLEY TONIGHT AND INTO SAN BERNARDINO COUNTY FRIDAY MORNING. THIS
PATH IS MORE INLAND THAN PREFERRED TO GET MUCH PRECIPITATION OVER
SOUTHWEST CA...ALTHOUGH COLD AIR ALOFT SKIRTS BY JUST TO OUR NORTH
TONIGHT NOT EXPECTING ANY THUNDERSTORM THREAT. THE COLD FRONT MOVES
ACROSS THE REGION VERY QUICKLY BUT WILL SUPPORT ISOLATED TO
SCATTERED SHOWERS BEFORE SUNRISE FRIDAY MORNING. RAINFALL TOTALS
WILL RANGE FROM 0.15 IN THE NORTH TO TRACE AMOUNTS IN MOST CASES.
NORTHERLY WINDS BEHIND THE STORM WILL KEEP MOISTURE UPSLOPING ON THE
NORTH SIDE OF THE MOUNTAINS FRIDAY WITH THIS AREA SEEING THE BEST
CHANCE OF PRECIPITATION. CLOUDS WILL RAPIDLY DECREASE TOMORROW
MORNING FOR THE REST OF THE REGION. IT WILL BE A LITTLE BREEZY WITH
NORTH WINDS ALONG THE I-5 CORRIDOR ACROSS THE SANTA CLARITA
VALLEY...SAN FERNANDO VALLEY AND THE SANTA MONICAS ON FRIDAY. COOLER
TEMPERATURES EXPECTED FOR THE MOUNTAINS WITH LITTLE CHANGE NEAR THE
COAST TOMORROW.

A SECOND STORM SYSTEM WILL MOVE ACROSS NORTHERN CA FRIDAY NIGHT AND
SATURDAY. WE WILL SEE PLENTY OF HIGHER CLOUDS ACROSS SOUTHWEST CA
FROM THIS SYSTEM WITH POSSIBLY A FEW LIGHT SHOWERS ALONG THE CENTRAL
COAST AND ACROSS THE MOUNTAINS BUT FOR THE MOST PART DRY CONDITIONS.
STRONG NORTHWEST FLOW ALOFT WILL TRANSLATE TO GUSTY SURFACE WINDS
ACROSS THE MOUNTAINS AND ANTELOPE VALLEY SATURDAY AFTERNOON. AT THIS
TIME WE EXPECT WIND GUSTS BETWEEN 40-50 MPH AND POSSIBLY HIGHER AT
TIMES INTO SATURDAY EVENING. WARMER AIR WILL BE ADVECTING INTO CA ON
SATURDAY SO TEMPERATURES WILL BE HIGHER THAN FRIDAY.

HIGH PRESSURE BEGINS TO BUILD ACROSS THE EASTERN PACIFIC OCEAN ON
SUNDAY WITH WARMER CONDITIONS AND LESS CLOUD COVER EXPECTED FOR
SOUTHWEST CA.

.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...20/1800Z.

AT 1800Z...AT 1725Z
OVER KLAX...THE BASE OF THE INVERSION WAS AT 5200 FEET AND THE TOP
OF THE INVERSION WAS LOCATED AT 7200 FEET WITH A TEMPERATURE OF 9C.

NORTH OF POINT CONCEPTION...GENERALLY LOW CONFIDENCE AS MARINE LAYER
CIGS BEGIN TO CLEAR BUT LOWER CIGS ASSOCIATED WITH APPROACHING COLD
FRONT WILL BRING PERIODIC MVFR/IFR CONDS AND OCCASIONAL LIGHT RAIN.
THE GREATEST THREAT OF -SHRA WILL BE BETWEEN 00Z-06Z. CIGS LIFTING
TO VFR AFTER 06Z.

SOUTH OF POINT CONCEPTION...MODERATE CONFIDENCE IN TAFS WITH MVFR
CIGS FOR COAST AND VALLEY SITES THROUGH 12Z. 30 PERCENT CHANCE OF
IFR CONDS 00Z-12Z FOR LA COUNTY VALLEYS.

KLAX...MODERATE CONFIDENCE IN TAFS...THERE IS A 40% CHANCE OF MVFR
CIGS FROM 20Z-00Z TODAY. AFTER 00Z THERE IS A 20% CHANCE OF IFR
CONDS DURING PERIODIC -SHRA. 20% CHANCE MVFR CIGS WILL LINGER
14Z-18Z.

BUR...MODERATE CONFIDENCE IN TAF. 30% CHANCE MVFR CIGS WILL DEVELOP
EARLIER THAN FORECAST OF 01Z. 40% CHANCE MVFR CIGS WITH -SHRA WILL
DEVELOP BY 04Z...AND LINGER THROUGH 18Z.

&&

.MARINE...20/200 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 INCREASING NW WINDS
WILL FILL INTO THE WESTERN PORTION OF PZZ650 AND 655 LATE THIS
AFTERNOON. THE STRONGER WINDS MAY BE DELAYED BY 2-3 HOURS FOR ZONE
655. HOWEVER...GUSTS TO 25 KNOTS ARE EXPECTED OVER THE WESTERN
PORTION OF THESE ZONES 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...BOLDT
AVIATION/MARINE...SMITH
SYNOPSIS...BOLDT

WWW.WEATHER.GOV/LOSANGELES





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