Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 311140 AAA
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
440 AM PDT FRI OCT 31 2014

...UPDATED AVIATION DISCUSSION...

.SYNOPSIS...

A FAST MOVING COLD FRONT WILL BRING PERIODS OF RAIN...MOUNTAIN
SNOW...POSSIBLE THUNDERSTORMS...AND GUSTY WINDS TO THE AREA TODAY
THROUGH SATURDAY. SUNDAY WILL BEGIN A WARMING TREND AS WE DRY
OUT...AND HIGH PRESSURE AND OFFSHORE FLOW RETURNS.

&&

.SHORT TERM (TODAY-SUN)...
MARINE LAYER JUST NOW STARTING TO GET GOING AS LIFT FROM THE
APPROACHING TROF ENTERS THE AREA. KEPT THE MORNING DRIZZLE IN THE
FORECAST BUT DO NOT HAVE THE GREATEST FEELING ABOUT IT. THE BEST
CHANCE OF DRIZZLE WILL BE NEAR THE FOOTHILLS. OTHER PROBLEM WITH
TODAYS FORECAST IS THE CLOUD FORECAST. SLO AND SBA COUNTIES WILL BE
MOSTLY CLOUDY ALL DAY NO PROBLEM BUT THE VTA AND LA COAST WILL BE A
LITTLE MORE PROBLEMATIC. THERE WILL BE PLENTY OF MORNING CLOUDS FOR
SURE AND THE DEEP MARINE LAYER SHOULD JUST CLEAR TO STRATACU DECK.
BUT CAN SEE THAT THERE IS A CHANCE THAT THE STRATUS TO JUST
DISSIPATE LEAVING PARTLY CLOUDY SKIES FOR THE AFTERNOON. IT WILL BE
COOLER TODAY WITH MAX TEMPS WILL BE IN THE UPPER 60S NORTH OF POINT
CONCEPTION AND IN THE LOWER 70S SOUTH OF POINT CONCEPTION.

SATELLITE SHOWS THE COLD CORE CU WRAPPED AROUND A 537 DM UPPER LOW A
COUPLE HUNDRED MILES WEST OF PORTLAND. A COLD FRONT IS DRAPED OVER
THE UPPER HALF OF THE WEST COAST XTNDG TO THE SW FROM THE BAY AREA.
IT REALLY LOOKS LIKE THE RAIN WILL HOLD OFF UNTIL THE AFTERNOON
ACROSS THE CENTRAL COAST. THE NAM ACTUALLY KEEP THE RAIN AWAY UNTIL
LATE EVENING. EXPECT RAIN TO START NEAR SAN SIMEON EARLY IN THE
AFTERNOON AND THEN REACH LOMPOC MID TO LATE AFTERNOON.

ALL THE REAL ACTION HAPPENS OVERNIGHT TONIGHT. A POTENT VORT MAX IS
FORECAST TO SWEEP INTO THE BACK OF THE SFC FRONT WHILE AT THE SAME
TIME A 500 MB COOL POCKET MOVES OVERHEAD DESTABILIZING THE
ATMOSPHERE. ALL OF THESE THINGS SHOULD COMBINE TO FORM A NICE
CONVECTIVE BURST THAT WILL LAST THROUGH THE EVENING INTO EARLY
SATURDAY MORNING. TRICK OR TREATERS IN SLO AND SBA COUNTY ARE FLAT
OUT OF LUCK TONIGHT. EARLIER IS BETTER FOR THE TRICK OR TREATERS FOR
VTA AND LA COUNTIES AS RAIN WILL LIKELY START TO DEVELOP SHORTLY
AFTER SUNSET.

THE BEST LIFT ENERGY AND INSTABILITY WILL OCCUR OVER SLO AND SBA
COUNTIES AND THIS IS GOOD ENOUGH FOR A SLIGHT CHC OF THUNDERSTORMS.
THE VORT MAX AND SFC FRONT WILL MOVE OVER THE AREA OVERNIGHT AND IT
LOOKS LIKE ALMOST EVERY AREAS WILL SEE 4 HOURS OF STEADY RAIN AND
PERHAPS A 1 TO 2 HOUR BURST OF HEAVIER RAIN. THE CENTRAL COAST WILL
SEE THE LONGEST STRETCH OF RAIN AND LIKELY THE HEAVIEST RAIN.

EARLY RAIN SEASON DISCLAIMER...THERE IS 20 PERCENT CHANCE THAT THE
VORT MAX AND FRONT WILL NOT PHASE TOGETHER AS NICELY AS THE MDLS ARE
FORECASTING AND IF THIS HAPPENS THIS EVENT WILL FIZZLE AND WHILE
PRODUCING SOME RAIN IT WILL NOT BE MUCH OF AN EVENT AT ALL.

COLD UNSTABLE AIR WILL MOVE IN SATURDAY. THIS WILL CREATE SOME GUSTY
WINDS ACROSS THE AREA NOTABLY NI THE MTNS AND THE ANTELOPE VLY.
RIGHT NOW IT LOOKS LIKE THERE WILL BE SOME LOCAL GUSTS TO 45 MPH BUT
NOT ENOUGH TO WARRANT ADVISORIES. IT WILL PRODUCE QUITE A BIT OF
INSTABILITY SHOWERS ESP IN THE MORNING BY AFTERNOON ENOUGH NVA MOVES
INTO THE AREA TO SQUASH MOST OF THE SHOWER ACTIVITY. THE BEST CHC OF
RAIN IN THE AFTERNOON WILL BE ACROSS THE NRN MTN SLOPES AND THE
FOOTHILLS OF THE SAN GABRIEL VLY. SHOWERS WILL LINGER INTO THE
EVENING ACROSS THESE TWO AREAS AS WELL AS POST FRONTAL WINDS WILL
PRODUCE ENOUGH UPSLOPE TO CREATE A SLIGHT CHC OF SHOWERS.

MAX RAINFALL RATES WILL BE ABOUT A THIRD OF AN INCH PER HOUR.
HEAVIER RAINFALL RATES UP TO AN INCH PER HOUR ARE POSSIBLE UNDER
THUNDERSTORMS. BY SATURDAY AFTERNOON MANY AREAS ON THE CENTRAL COAST
WILL SEE RAINFALL TOTALS AROUND 1 INCH...WITH HIGHER AMOUNTS
POSSIBLE FOR THE COASTAL SLOPES OF NORTHERN SAN LUIS OBISPO COUNTY.
THE REST OF THE NON-DESERT AREAS SHOULD RECEIVE ABOUT ONE-QUARTER TO
THREE-QUARTERS OF AN INCH OF RAIN...EXCEPT FOR THE FOOTHILL AREAS OF
THE SAN GABRIELS...WHICH COULD SEE UP TO 1 INCH.

NOW LEVELS WILL START OUT OVER 7000 FEET FRIDAY NIGHT...THEN FALL TO
AROUND 6000 FEET BY SATURDAY. SOME LIGHT 1 TO 3 INCH ACCUMULATIONS
ARE POSSIBLE AT ELEVATIONS OVER 6500 FEET IN THE VENTURA AND LOS
ANGELES COUNTY MOUNTAINS.

WITH 559 DM HGTS OVERHEAD SATURDAY LOOK FOR THE COLDEST DAY SINCE
APRIL 13TH WITH CSTL AND VLY TEMPS ONLY IN THE 60S OR 6 TO 12
DEGREES BLO NORMAL.

CONTINUED BREEZY AND COOL FOR SUNDAY AS THE TROF SLOWLY MOVES OFF TO
THE EAST. SKIES WILL CLEAR THROUGH THE DAY. IT WILL BE BREEZY ESP IN
THE MTNS AND THE ANTELOPE VLY. MAX TEMPS WILL RISE A DEGREE OR TWO
FROM SATURDAYS CHILLY READINGS BUT WILL STILL BE BELOW NORMAL.

.LONG TERM (MON-THU)...
AND THEN ITS ALL OVER AND SOCAL IS BACK TO SUNSHINE AND ABOVE NORMAL
TEMPS. ALL MDLS AGREES THAT A RIDGE TO OUR SW  WILL START TO BUILD
INTO THE STATE ON MONDAY CONTINUE TO GROW ON TUESDAY...PEAK ON
WEDNESDAY AND THEN WEAKEN A LITTLE THU. WEAK OFFSHORE FLOW EACH
MORNING SHOULD KEEP THE LOW CLOUDS AWAY. MAX TEMPS WILL RISE EACH
DAY REACHING AT EXCEEDING NORMAL BY TUESDAY. WEDNESDAY LOOKS TO BE
THE WARMEST DAY WITH ALMOST ALL CST AND VLY TEMPS IN THE 80S. STILL
WARM BUT MAYBE 2 TO 3 DEGREES COOLER THU.

&&

.AVIATION...31/1140Z...

THE MARINE LAYER AT KLAX AT 1125Z WAS NEAR 3300 FT DEEP. THE
INVERSION TOP WAS NEAR 4200 FEET WITH A TEMPERATURE OF 14 DEGREES C.

OVERALL...LOW TO MODERATE CONFIDENCE IN 12Z TAF PACKAGE. MVFR/IFR
STRATUS DECK HAS FILLED IN OVER ALL COASTAL/VALLEY TAF SITES EARLY
THIS MORNING. EXPECT MVFR/IFR CONDS TO CONTINUE THRU THE MORNING.
FOR THIS AFTERNOON...CENTRAL COAST SHOULD REMAIN MVFR WITH FRONT
APPROACHING WHILE SOUTH OF POINT CONCEPTION CIGS SHOULD RANGE FROM
MVFR TO VFR.

COLD FRONT WILL BEGIN TO IMPACT THE NORTHERN TAF SITES LATE THIS
AFTERNOON...THEN MOVE SOUTHWARD THIS EVENING. MVFR CONDS WITH STEADY
LIGHT RAIN CAN BE EXPECTED...WITH MODERATE CONFIDENCE IN TIMING OF
STEADY RAINFALL. ADDITIONALLY THERE WILL BE A SLIGHT CHANCE OF
THUNDERSTORMS ACROSS SANTA BARBARA AND SAN LUIS OBISPO COUNTIES THIS
EVENING AND EARLY SATURDAY MORNING AS COLD AND UNSTABLE AIR FILTERS
IN BEHIND THE COLD FRONT.

KLAX...MODERATE CONFIDENCE IN 12Z TAF. MODERATE CONFIDENCE IN VFR
CIGS DEVELOPING THIS AFTERNOON. TIMING OF BEGINNING OF STEADY
RAINFALL WITH FRONT COULD BE +/- 2 HOURS OF CURRENT 09Z FORECAST.

KBUR...MODERATE CONFIDENCE IN 12Z TAF. MODERATE CONFIDENCE IN MVFR
CIGS CONTINUING THROUGH THIS AFTERNOON. TIMING OF BEGINNING OF
STEADY RAINFALL WITH FRONT COULD BE +/- 2 HOURS OF CURRENT 10Z
FORECAST.

&&

.MARINE...31/230 AM...

FOR THE OUTER WATERS...MODERATE CONFIDENCE IN THE DEVELOPMENT OF
SMALL CRAFT LEVEL NORTHWEST WINDS THIS EVENING BEHIND THE COLD
FRONT. FOR SATURDAY THROUGH MONDAY...MODERATE NORTHWEST FLOW WILL
CONTINUE...AND SMALL CRAFT CONDITIONS ARE LIKELY.

FOR THE INNER WATERS...WINDS ARE GENERALLY EXPECTED TO REMAIN BELOW
SMALL CRAFT LEVELS THROUGH EARLY NEXT WEEK. HOWEVER...LOCAL SMALL
CRAFT LEVEL GUSTS WILL BE POSSIBLE SATURDAY THROUGH SUNDAY ACROSS
THE WESTERN PART OF THE SANTA BARBARA CHANNEL.

BEHIND THE COLD FRONT...COLD AND UNSTABLE AIR WILL RESULT IN THE
SLIGHT CHANCE OF THUNDERSTORMS THIS EVENING THROUGH EARLY SATURDAY
MAINLY NORTH AND WEST OF THE CHANNEL ISLANDS. THE USUAL THUNDERSTORM
HAZARDS WILL BE POSSIBLE...GUSTY WINDS...BRIEF HEAVY
RAIN...LIGHTNING...AND EVEN WATERSPOUTS.

A 10-12 FOOT NORTHWEST SWELL IS EXPECTED TO MOVE THROUGH THE OUTER
WATERS SATURDAY AND SUNDAY.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).
MARINE WEATHER STATEMENT (SEE LAXMWSLOX).
SPECIAL WEATHER STATEMENT (SEE LAXSPSLOX).

&&

$$

PUBLIC...RORKE
AVIATION/MARINE...RAT
SYNOPSIS...B

WWW.WEATHER.GOV/LOSANGELES





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