Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 011134 AAA
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
430 AM PDT WED OCT 1 2014

...UPDATED AVIATION DISCUSSION...

.SYNOPSIS...

A SIGNIFICANT WARMING TREND IS EXPECTED INTO THE WEEKEND AS SURFACE
HIGH PRESSURE BUILDS INTO THE GREAT BASIN AND OFFSHORE FLOW
STRENGTHENS THROUGH LATE THIS WEEK. WEAKER OFFSHORE FLOW IS EXPECTED
FOR THE WEEKEND...BUT HOT AND DRY WEATHER WILL CONTINUE AS HIGH
PRESSURE BUILDS ALOFT. COOLER WEATHER IS POSSIBLE EARLY TO MID NEXT
WEEK.

&&

.SHORT TERM (TODAY-FRI)...LATEST ACARS SOUNDING AROUND LAX INDICATED
A STRENGTHENING INVERSION AROUND 1000 FT DEEP THIS MORNING. AN EDDY
CIRCULATION HAS ALSO DEVELOPED ALLOWING FOR PATCHY LOW CLOUDS TO
RANDOMLY DEVELOP ACROSS THE SOCAL BIGHT...ORANGE COUNTY AS WELL AS
THE SOUTHERN PORTION OF THE SAN GABRIEL VALLEY. WITH THE INVERSION
THIS DEEP AND THE EDDY CIRCULATION IN PLACE...EXPECT PATCHY LOW
CLOUDS TO MOVE IN ACROSS THE LA COUNTY COAST...AND POSSIBLY PORTIONS
OF THE SAN GABRIEL VALLEY. LESS CONFIDENT FOR STRATUS TO MAKE IT
INTO VENTURA COUNTY AT THIS POINT. THERE WERE PATCHY LOW CLOUDS
ACROSS THE SANTA BARBARA CENTRAL COAST AND SANTA YNEZ VALLEY. SOME
PATCHY DENSE FOG WILL BE LIKELY FOR AREAS N OF POINT CONCEPTION THIS
MORNING.

SYNOPTICALLY...BROAD NW FLOW WILL CONTINUE OVER THE FORECAST AREA
TODAY AS AN UPPER LEVEL HIGH STRENGTHENS TO ITS WEST OVER THE ERN
PAC. BY THURSDAY THE UPPER RIDGE WILL PUSH INTO CALIFORNIA WITH THE
UPPER HIGH PARKED OVER SOUTHERN AND CENTRAL CALIFORNIA. THIS PATTERN
WILL PERSIST THROUGH AT LEAST SUNDAY BEFORE THE RIDGE BEGINS TO
BREAKDOWN AS A WEAK UPPER TROUGH MOVES CLOSER TO CALIFORNIA FOR THE
BEGINNING OF NEXT WEEK. AT THE LOWER LEVELS...A SURFACE HIGH WILL
DEVELOP OVER NORTHERN NEVADA. THIS WILL CREATE A TIGHTENING OFFSHORE
SURFACE GRADIENT OVER SOUTHERN CALIFORNIA BEGINNING TODAY...THEN
STRENGTHEN ON THURSDAY MORNING. THE RESULTS WILL BE A SIGNIFICANT
WARMING TREND ACROSS THE ENTIRE FORECAST AREA BY THURSDAY...WITH
ADDITIONAL WARMING ACROSS THE COAST AND COASTAL VALLEYS AS WEAK TO
MODERATE SANTA ANA WINDS CONTINUE INTO FRIDAY MORNING...THEN WEAKER
EACH MORNING AFTER THAT THROUGH SUNDAY.

FOR TODAY...THERE WILL BE WEAK OFFSHORE FLOW ACROSS THE INTERIOR
SECTIONS INCLUDING THE MOUNTAINS AND ADJACENT WIND PRONE LA/VTU
COUNTY VALLEY PASSES AND CANYONS. EXPECT MAX TEMPS TO BE A FEW
DEGREES WARMER ACROSS THE INTERIOR TODAY...EXCEPT THE ANTELOPE
VALLEY SHOULD LOWER A FEW DEGREES WITH THE OFFSHORE FLOW. THE TRICKY
PART FOR TODAY WILL BE THE COASTAL TEMPS. A CATALINA EDDY DEVELOPED
LAST NIGHT AND THE MARINE LAYER DEPTH WAS AROUND 1000 FT THIS
MORNING...THIS SHOULD KEEP THE COASTAL TEMPS A TAD COOLER THIS
MORNING BUT SHOULD WARM UP LATE THIS MORNING AS THE MARINE LAYER
INFLUENCE MIXES OUT. TEMPS SHOULD BE SIMILAR OR A FEW DEGREES WARMER
ACROSS THE LA/VTU COAST TODAY. AS THE UPPER HIGH MOVES OVERHEAD
TONIGHT INTO THURSDAY...THE MARINE LAYER WILL BE VERY SHALLOW AND
OFFSHORE WINDS WILL STRENGTHEN ACROSS THE LA/VTU COUNTY MOUNTAINS
LATE THIS EVENING THEN SPREAD INTO THE WIND PRONE VALLEY AND COASTAL
AREAS BY EARLY THURSDAY MORNING. LATEST NAM-WRF MODEL IS SUGGESTING
THE LAX-DAG GRADIENT WILL BE AROUND -5.4MB BY 5 AM THU MORNING. THIS
UPCOMING WIND EVENT IS MAINLY SURFACE GRADIENT DRIVEN. THERE WILL
NOT BE MUCH UPPER SUPPORT TO DRIVE THE WINDS STRONGER AS THE UPPER
HIGH WILL BE DIRECTLY OVER THE REGION. WIND ADVISORIES WILL LIKELY
BE NEEDED FOR THE LA/VTU COUNTY MOUNTAINS...SANTA CLARITA
VALLEY...VENTURA COUNTY VALLEYS AND POSSIBLY THE NW PORTION OF THE
SAN FERNANDO VALLEY FOR THURSDAY MORNING. LATER SHIFTS WILL TAKE A
LOOK AT THIS AS WE DRAW CLOSER TO THE FIRST SANTA ANA OF THE SEASON.
NOT EXPECTING MUCH IN THE WAY OF LOW CLOUDS OVERNIGHT INTO THURSDAY
MORNING AS GUSTY NE WINDS SHOULD SCOUR OUT ANY STRATUS. WITH THE
WINDS EXPECTED TO BE STRONGER THURSDAY MORNING...EXPECT HIGH TEMPS
TO RISE SIGNIFICANTLY ACROSS MANY COASTAL AREAS AS WELL AS THE
COASTAL VALLEYS. WARMEST VALLEY LOCATIONS REACHING THE MID TO UPPER
90S. THE ANTELOPE VALLEY SHOULD BE EVEN COOLER ON THURSDAY WITH
HIGHS ONLY IN THE LOWER TO MID 80S. THE STRONGEST WINDS WILL OCCUR
THURDAY MORNING...WITH SLIGHTLY WEAKER WINDS EXPECTED ON FRIDAY
MORNING. HIGHEST TEMPS OF THE WEEK ARE EXPECTED TO BE FRI AND SAT.
FOR FRIDAY THERE WILL BE TRIPLE DIGIT READINGS ACROSS THE LA/VTU
COUNTY COASTAL VALLEYS AND UP THE MID 90S ACROSS THE COASTAL PLAIN.

ALTHOUGH WINDS WILL NOT BE AN ISSUE FOR THE SBA/SLO COUNTIES...THERE
WILL BE SOME VERY WARM TEMPS ACROSS THE COASTAL AREAS AS WEAK
OFFSHORE FLOW PERSISTS...ESPECIALLY THU-FRI. DONT BE SURPRISED TO
SEE AVILA BEACH TO REACH 90 WITH SOME DOWNSLOPING EXPECTED ACROSS
THE ADJACENT FOOTHILL.

.LONG TERM (SAT-TUE)...AT THIS TIME...IT LOOKS LIKE SATURDAY WILL
THE BE THE HOTTEST DAY OF THE WEEK WITH HIGH TEMPS BETWEEN 101-106
FOR THE LA/VTU COUNTY COASTAL VALLEYS AND THE UPPER 90S FOR DOWNTOWN
LA AND LONG BEACH. THERE SHOULD BE A FEW DEGREES OF COOLING ON
SUNDAY...BUT STILL VERY HOT. THE UPPER HIGH BEGINS TO BREAKDOWN AS A
WEAK UPPER TROUGH APPROACHES CALIFORNIA. EXPECT TEMPERATURES TO
REMAIN WELL ABOVE NORMAL THROUGH MONDAY...WITH SOME RELIEF POSSIBLE
BY TUESDAY...ESPECIALLY ACROSS THE COASTAL AREAS AS NIGHT THROUGH
MORNING LOW CLOUDS SHOULD AFFECT THE COASTAL AREAS. IT WILL REMAIN
QUITE WARM THROUGH THE EXTENDED PERIOD...BUT NOT AS HOT AS THE
WEEKEND.

&&

.AVIATION...01/1130Z...

MARINE LAYER AT KLAX AT 0815Z WAS 900 FEET DEEP AND THE INVERSION
TOP WAS 2700 FEET WITH A TEMPERATURE OF 21 DEGREES C.

OVERALL...MODERATE CONFIDENCE IN 12Z TAF PACKAGE. IN THE IMMEDIATE
SHORT TERM...LOW CONFIDENCE IN MOST COASTAL TAF SITES DUE TO THE
SOMEWHAT CHAOTIC NATURE OF THE STRATUS. ONCE THIS STRATUS CLEARS OUT
BY LATE THIS MORNING...HIGH CONFIDENCE IN VFR CONDS PREVAILING THIS
AFTERNOON THROUGH TONIGHT.

KLAX...OVERALL...MODERATE CONFIDENCE IN 12Z TAF. LOW CONFIDENCE IN
TAF FROM 12Z THRU 17Z AS THERE IS A 50% CHANCE THAT CIG RESTRICTIONS
WILL NOT DEVELOP AS FORECAST. BEYOND 17Z...HIGH CONFIDENCE IN VFR
CONDS PREVAILING THRU THE REMAINDER OF THE TAF PERIOD.

KBUR...OVERALL...HIGH CONFIDENCE IN 12Z TAF.

&&

.MARINE...01/200 AM...

FOR THE OUTER WATERS...EXPECT NORTHWEST WINDS TO DIMINISH IN THE
NEXT FEW HOURS...SO WILL LET THE SMALL CRAFT ADVISORIES EXPIRE AND
WILL MENTION LOCAL GUST TO 25 KT THROUGH TODAY. FOR TONIGHT AND
THROUGH THE WEEKEND...WINDS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT
ADVISORY LEVELS.

FOR THE INNER WATERS...HIGH CONFIDENCE IN WINDS REMAINING BELOW
ADVISORY LEVELS THROUGH THIS EVENING. BY LATE TONIGHT AND THURSDAY
HIGH CONFIDENCE IN NORTHEAST WINDS DEVELOPING WITH A CHANCE OF WINDS
REACHING SMALL CRAFT ADVISORY THRESHOLDS THURSDAY MORNING
(ESPECIALLY NEAR SHORE) FROM VENTURA TO MALIBU AND OUT TO THE
ISLANDS. FOR FRIDAY THROUGH THE WEEKEND...WEAK OFFSHORE FLOW CAN BE
EXPECTED AT NIGHT...AND WEAK ONSHORE FLOW IN THE AFTERNOON/EVENING
HOURS.

A LONG PERIOD SOUTH-SOUTHWEST SWELL IS ANTICIPATED TO ARRIVE ON
WEDNESDAY AND CONTINUE THROUGH FRIDAY.

&&

.FIRE WEATHER...CRITICAL FIRE WEATHER CONDITIONS ARE EXPECTED TO
DEVELOP ACROSS MUCH OF VENTURA AND LOS ANGELES COUNTIES TONIGHT
AS OFFSHORE GRADIENTS INCREASE AND HUMIDITIES FALL. NORTHEAST WINDS
WILL ACTUALLY BEGIN AS EARLY AS THIS MORNING ACROSS THE MOUNTAINS
VALLEYS, HOWEVER HUMIDITIES ARE EXPECTED TO REMAIN ABOVE 20 PERCENT
IN MOST AREAS UNTIL TONIGHT WHEN MUCH DRIER AIR MOVES IN. THE
STRONGEST WINDS ARE EXPECTED TONIGHT THROUGH EARLY AFTERNOON
THURSDAY WITH GUSTS UP TO 40 MPH IN THE MOUNTAINS AND 25-30 MPH IN
THE VALLEYS. HUMIDITIES THURSDAY WILL GENERALLY RANGE FROM 10-15
PERCENT.

NORTHEAST WINDS ARE EXPECTED TO BE WEAKER THURSDAY NIGHT INTO FRIDAY
BUT STILL REMAIN GUSTY AT TIMES. VERY POOR HUMIDITY RECOVERIES ARE
EXPECTED THURSDAY NIGHT WITH WIDESPREAD SINGLE DIGIT HUMIDITIES
FRIDAY THROUGH SUNDAY.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
FIRE WEATHER WATCH (SEE LAXRFWLOX).
SPECIAL WEATHER STATEMENT (SEE LAXSPSLOX).

&&

$$

PUBLIC...KAPLAN
AVIATION/MARINE...RAT
FIRE...MW
SYNOPSIS...SUKUP

WWW.WEATHER.GOV/LOSANGELES




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