FXUS66 KLOX 091823
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1024 AM PST WED DEC 9 2009

UPDATED AVIATION SECTION

.SYNOPSIS...

EXTREMELY COLD TEMPERATURES ARE EXPECTED TONIGHT. A STORM SYSTEM 
WILL BRING A CHANCE OF RAIN ON THURSDAY...SNOW LEVEL ABOVE 5500 
FEET.  ANOTHER STORM SYSTEM IS FORECASTED FOR THE WEEKEND...WITH THE 
POTENTIAL TO CONNECT WITH SOME TROPICAL MOISTURE THAT COULD PRODUCE 
COPIOUS AMOUNTS OF PRECIPITATION. 

&&

.SHORT TERM (TODAY-FRI)...OVERALL...ANOTHER VERY COOL MORNING ACROSS
THE DISTRICT...BUT NOT QUITE AS COLD AS YESTERDAY. ALL FROST/FREEZE
PRODUCTS HAVE BEEN EXPIRED OR CANCELLED FOR THE DAY.

FORECAST WISE...THE CURRENT PACKAGE LOOKS ON TRACK. QUICK LOOK AT
12Z MODELS SHOWS AN EXTENDED WET PERIOD ON TAP FOR THE AREA. THE
FIRST SYSTEM WILL MOVE THROUGH THURSDAY AND FRIDAY. AT THIS TIME
MODELS CONTINUE TO INDICATE THIS FIRST SYSTEM WILL ARRIVE IN TWO
WAVES. THE FIRST WAVE ON THURSDAY WILL BRING THE BEST CHANCE OF
RAIN TO SLO/SBA COUNTIES. THE SECOND WAVE WILL MOVE THROUGH
THURSDAY NIGHT...BRINGING A BETTER CHANCE OF RAIN TO VTU/LAX 
COUNTIES. WITH THIS FIRST SYSTEM...RAINFALL AMOUNTS ARE EXPECTED
TO RANGE BETWEEN 0.25 AND 0.75 INCHES WITH LOCAL AMOUNTS AROUND
1.00 INCH IN FAVORED UPSLOPE AREAS. SNOW LEVELS SHOULD REMAIN 
AROUND 6000 FEET.

A SECOND...MORE SIGNIFICANT...SYSTEM IS FORECAST TO MOVE ACROSS
THE AREA. PER 12Z MODELS...THIS SYSTEM LOOKS MORE POTENT WITH 
GOOD SOUTHERLY WINDS AHEAD OF THE SYSTEM WHICH WOULD HELP PRODUCE
HIGHER RAINFALL AMOUNTS. WILL PROVIDE MORE DETAILS WITH THE 
AFTERNOON PACKAGE.

*** LONG TERM FROM PREVIOUS DISCUSSION ***

.LONG TERM (SAT-TUE)...

THE LONG RANGE MDLS ARE ALL IN PRETTY GOOD AGREEMENT FOR THE LONG 
TERM FORECAST. RAIN WILL AGAIN OVERSPREAD THE AREA SATURDAY. THE GFS 
IS ABOUT 6 HOURS FASTER WITH THE RAIN THAN THE NAM SO THE MORNING 
MAY BE RAIN FREE. THIS STORM HAS SEVERAL VORT LOBES WITH IT AND 
THERE WILL LIKELY BE PERIODS OF RAIN THROUGH SUNDAY MORNING. 
PRELIMINARY RAINFALL ESTIMATES FOR THIS STORM ARE AROUND AN INCH 
COAST AND VLYS AND ONE AND HALF TO TWO AND HALF IN THE MOUNTAINS. 
THE LONG RANGE MDLS HAVE NOT BEEN PREFORMING WELL WITH RAINFALL 
AMOUNTS LATELY SO WOULD NOT BUT A LOT OF STOCK IN THE THESE NUMBERS. 
THIS STORM HAS A MORE NORTHERLY TRAJECTORY WITH IT AND WHILE SNOW 
LEVELS WILL START OUT AROUND 6000 FEET THEY WILL LIKELY LOWER SUNDAY 
WITH THE ARRIVAL OF THE COLDER AIR.

THE STORM SHOULD TAPER OFF SUNDAY AFTERNOON AND OVERNIGHT. A LITTLE 
RIDGE POPS UP MONDAY AND TUESDAY AND SHOULD ALL FOR A COUPLE OF DRY 
DAYS WITH TEMPS CLIMBING TOWARDS BUT NOT TOO NORMAL.

&&

.AVIATION...09/1800Z.

BROAD MID/UPPER LEVEL TROUGH OF LOW PRESSURE CENTERED UPSTREAM AND 
EXTENDING OVER THE AREA WILL APPROACH. MODERATE MID/UPPER LEVEL WEST 
SOUTHWEST WINDS WILL PREVAIL AND BECOME MOIST OVER THE AREA. 
FREEZING LEVEL RANGED FROM AROUND 4KFT OVER THE EAST HALF TO AROUND 
9.5KFT WEST HALF THIS MORNING WILL ASCEND TO AROUND 9KFT EAST HALF 
AND DESCEND A FEW HUNDRED WEST HALF. A WEAK PRESSURE GRADIENT WILL 
PERSIST OVER THE AREA. 

KLAX...THERE IS CHANCE CIGS AROUND 040 WILL DEVELOP AFTER 10/12Z 
WITH LIGHT RAIN AFTER 10/15Z.

KBUR...VERY LIKELY LAYERED CIGS 060/100 WILL DEVELOP BY 10/15Z.

VIRTUALLY CERTAIN - 95-100%
VERY LIKELY       - 80-95%
LIKELY            - 60-80%
CHANCE            - 30-60%
VERY UNLIKELY     - 20% OR LESS

&&

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

&&

$$

PUBLIC...THOMPSON
AVIATION...30
SYNOPSIS...ASR

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