Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 240434
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
830 PM PDT SAT MAY 23 2015

.SYNOPSIS...
A SERIES OF WEAK LOW PRESSURE TROUGHS WILL CONTINUE THE PERSISTENT NIGHT
THROUGH MORNING LOW CLOUDS AND BELOW NORMAL TEMPERATURES THROUGH THE MIDDLE
OF NEXT WEEK. A RIDGE OF HIGH PRESSURE SHOULD BRING WARMING TOWARD
THE END OF NEXT WEEK.

&&

.SHORT TERM (TONIGHT-TUE)...
CLOSED UPPER LEVEL LOW PRESSURE SYSTEM MOVING THROUGH CENTRAL CALIFORNIA
THIS EVENING...CURRENTLY CENTERED NEAR FRESNO AS OF 8 PM. THIS SYSTEM HAS
SOME FAIRLY COLD AIR ALOFT FOR THIS TIME OF YEAR WITH 500 MB TEMPERATURES
OF -19 DEGREES CELSISUS AT THE CORE OF THE SYSTEM. THE INSTABILITY ASSOCIATED
WITH THE COLD AIR ALOFT HAS GENERATED ISOLATED SHOWER AND THUNDERSTORM ACTIVITY
THIS EVENING ACROSS THE CENTRAL VALLEY AND SOUTHERN SIERRAS. THE LEADING EDGE OF
THUNDERSTORM ACTIVITY IS PASSING JUST EAST OF THE NORTHEAST CORNER OF SLO COUNTY
MOVING INTO NORTHWEST KERN COUNTY. THE UPPER LEVEL LOW PRESSURE SYSTEM IS EXPECTED
TO CONTINUE SPREADING SOUTHEASTWARD TONIGHT...BRINGING INCREASED CLOUDS AND ISOLATED
SHOWERS TONIGHT ACROSS THE MOUNTAINS AND ANTELOPE VALLEY. IN EVENING UPDATE...WILL EXPAND
THE ISOLATED SHOWER ACTIVITY AND INCLUDE A SLIGHT CHANCE OF THUNDERSTORMS FOR AREAS
ADJACENT TO KERN COUNTY LINE (WHERE THERE WILL BE BEST INSTABILITY). IN ADDITION...THE
PASSAGE OF THIS LOW PRESSURE SYSTEM TO THE NORTH MAY PROVIDE SOME ADDITIONAL LIFT FOR
THE MOIST LAYER IN LA COUNTY TO GENERATE SOME PATCHY DRIZZLE...SO THAT WILL ALSO BE INCLUDED
IN EVENING UPDATE. IN ADDITION...THERE COULD BE SOME DRIZZLE ACROSS PORTIONS OF LA COUNTY
TONIGHT AS THE PASSAGE OF THE LOW PRESSURE SYSTEM COULD PROVIDE SOME ADDITIONAL LIFT FOR
THE LOW LEVEL MOIST LAYER. SOME GUSTY NORTHWEST WINDS WILL IMPACT THE ANTELOPE
VALLEY...MOUNTAINS...AND SBA SOUTH COAST TONIGHT IN ASSOCIATION WITH THIS WEATHER
SYSTEM...BUT MOSTLY EXPECTED TO REMAIN BELOW ADVISORY THRESHOLDS.

THIS WEATHER SYSTEM WILL BE QUICK HITTING TONIGHT THEN MOVE RAPIDLY EASTWARD
ON SUNDAY WITH BUILDING HEIGHTS THROUGH THE DAY. AS A RESULT...EXPECTING BETTER
CLEARING ACROSS INTERIOR SECTIONS WITH SOME WARMING ON SUNDAY AFTERNOON.

*** FROM PREVIOUS DISCUSSION ***

A SERIES OF WEAK TROUGHS WILL CONTINUE TO RIPPLE THROUGH THE AREA
INTO EARLY NEXT WEEK CONTINUING COOLER THAN NORMAL CONDITIONS AND
PERSISTENT MARINE LAYER STRATUS DECK. THERE IS A CHANCE THAT THE
MARINE LAYER STRATUS DECK COULD A BE BIT DEEPER THAN THE CURRENT
FORECAST...ESPECIALLY BETWEEN TUESDAY NIGHT AND WEDNESDAY WHEN A
SLIGHTLY STRONGER TROUGH APPROACHES. STRATUS INTRUSION COULD OCCUR
ACROSS THE SANTA CLARITA VALLEY AND INTO THE COASTAL SLOPES OF THE
MOUNTAINS INTO TUESDAY OR WEDNESDAY.

.LONG TERM (WED-SAT)...

A TROUGH SHOULD MOVE OVER THE AREA ON WEDNESDAY BUT SHOULD EXIT THE
REGION BETWEEN WEDNESDAY NIGHT AND THURSDAY. HIGH PRESSURE SHOULD
BUILD IN FOR LATE NEXT WEEK AND BRING A WARMING TREND WITH LESS
MARINE INTRUSION AWAY FROM THE COAST. GFS MODEL SOLUTIONS SUGGEST
ONSHORE SURFACE GRADIENTS DIMINISHING INTO LATE WEEK BUT STILL
REMAIN ONSHORE INTO NEXT SATURDAY. A SHARPER WARMING TREND SHOULD BE
EXPECTED AWAY FROM THE COAST. THERE IS A POSSIBILITY THAT A
PERSISTENCE FORECAST MAY BE THE BEST FORECAST FOR LATE WEEK FOR THE
COASTAL AND LOWER VALLEY AREAS AS A MAY GRAY PATTERN DEVELOPS TO
FINISH OUT THE MONTH OF MAY.

&&

.AVIATION...23/2335Z.

LOW TO MODERATE CONFIDENCE IN THE 00Z TAF FORECAST PACKAGE. DEEP LOW LEVEL
MOIST LAYER COMBINED WITH STRONG ONSHORE FLOW CONTINUES TO GENERATE STRATOCUMULUS
CLOUDS ACROSS VALLEYS AND MOUNTAINS OF LA/VENTURA COUNTIES. AN APPROACHING LOW
PRESSURE SYSTEM WILL BRING INCREASING LOWER TO MID LEVEL CLOUDS ACROSS MOST OF
THE FORECAST AREA OVERNIGHT. CIGS WILL BE GENERALLY MVFR/VFR AND THERE WILL BE
ISOLATED LIGHT SHOWERS OR DRIZZLE ACROSS THE FORECAST AREA...ESPECIALLY OVER THE
MOUNTAINS AND FOOTHILLS. EDDY CIRCULATION WILL BRING SOUTH TO SOUTHEAST WINDS 5 TO 10
KT ACROSS LA BASIN BY EARLY SUNDAY MORNING.

LAX...MODERATE CONFIDENCE IN 00Z TAF. EXPECTING MVFR CIGS TO REDEVELOP TONIGHT
BUT TIMING REAMINS IN QUESTION...MOST LIKELY IN THE 03-05Z RANGE. EDDY CIRCULATION
WILL BRING SOUTHEAST WINDS BY EARLY SUNDAY MORNING...WITH A 30 PERCENT CHANCE OF
BRIEFLY REACHING 10KT SOMETIME BETWEEN 12Z AND 18Z. EXPECTING VFR CIGS TO LINGER
INTO AFTERNOON...BUT 30% CHANCE OF SCT CONDITIONS ON SUNDAY AFTERNOON.

KBUR...SCT-BKN040 CONDITIONS THE NEXT FEW HOURS THEN VFR CIGS GENERALLY PREVAILING
TONIGHT INTO SUNDAY. EDDY CIRCULATION LIKELY TO ENHANCE SOUTHEAST FLOW AND DEEPENING
MARINE LAYER ON SUNDAY MORNING. EXPECTING VFR CIGS TO LINGER INTO AFTERNOON...BUT
20% CHANCE OF SCT CONDITIONS ON SUNDAY AFTERNOON.

&&

.MARINE...23/800 PM.

OUTER WATERS...HIGH CONFIDENCE IN SMALL CRAFT ADVISORY NORTHWEST
WINDS FOR ALL OUTER WATERS THROUGH LATE TONIGHT.  BY SUNDAY WINDS LOOK TO
BE SLIGHTLY WEAKER BUT THERE IS A 30% CHANCE THE SCA WILL NEED TO BE
EXTENDED THROUGH THE MORNING HOURS.

INNER WATERS...THERE WILL BE SMALL CRAFT ADVISORY WINDS FOR THE
WESTERN PORTION OF THE SANTA BARBARA CHANNEL TONIGHT. LOCAL GUSTS UP
TO 20 KNOTS WILL AFFECT THE WESTERN PORTION OF PZZ655 THIS EVENING.


&&

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

&&

$$

PUBLIC...GOMBERG/HALL
AVIATION/MARINE...GOMBERG
SYNOPSIS...B

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