FXUS66 KLOX 100428
AFDLOX
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
828 PM PST WED DEC 9 2009
.SYNOPSIS...COLD TEMPERATURES ARE EXPECTED FOR TONIGHT. AN
UNSETTLED PATTERN WILL REDEVELOP THROUGH THURSDAY AS A WEAK STORM
WILL BRING A CHANCE OF RAIN WITH SNOW ABOVE 5000 FEET...MAINLY
THURSDAY NIGHT AND FRIDAY. A STRONGER STORM SYSTEM WILL PUSH A
MOIST AND UNSTABLE AIR MASS OVER THE AREA THROUGH THE WEEKEND.
HIGH PRESSURE WILL BUILD OVER THE REGION FOR EARLY NEXT WEEK.
&&
.UPDATE...MAINLY HIGH LEVEL MOISTURE IS INCREASING OVER THE AREA
THIS EVENING AS WEAK RIDGING CONTINUES TO BREAK DOWN AND A WEAK
TROUGH APPROACHES. A FEW SHOWERS CAN BE SEEN ON KVBX RADAR
CURRENTLY. ANY RAINFALL FROM THESE SHOWERS IS LIKELY VIRGA AND
HIGH-BASED AT THIS TIME. OTHER THAN A FEW SPRINKLES AND SOME
LOCALLY BREEZY CONDITIONS NEAR SHOWERS...IT WILL LIKELY REMAIN
DRY THROUGH THURSDAY AFTERNOON. MODEL SOLUTIONS ARE CONTINUING TO
BACK OFF THE TIMING FOR ANY PRECIPITATION ON THURSDAY...PUSHING
THE BULK OF THE PRECIPITATION TO THURSDAY NIGHT AND FRIDAY WITH
THE FRONTAL BOUNDARY. IN ADDITION...MODEL LAG SHIFT OF THE RIDGE
AXIS UNTIL LATE THURSDAY AFTERNOON...NOT BODING WELL FOR SHOWERS.
THE PACKAGE WILL AMENDED TO TREND DOWN ON POPS FOR THE NEXT 24
HOURS AND FOCUSING HIGHEST POP ON THURSDAY NIGHT AND FRIDAY.
&&
.PREV DISCUSSION... /ISSUED 200 PM PST WED DEC 9 2009/
SHORT TERM...BY THURSDAY NIGHT/FRIDAY MORNING...LIKELY POPS ARE
EXPECTED FOR ALL AREAS WITH THE RAIN THREAT TAPERING OFF FRIDAY
AFTERNOON. AT THIS TIME...THIS SYSTEM LOOKS RATHER WEAK...WITH
0.25" TO 0.75" OF RAINFALL EXPECTED FOR MOST AREAS. SNOW LEVELS
WILL GENERALLY BE BETWEEN 5500 AND 6000 FEET WITH 2-4 INCHES OF
SNOWFALL ACCUMULATION EXPECTED. WITH THE EXPECTED RAIN AND SNOW
AMOUNTS...DO NOT ANTICIPATE THE NEED FOR ANY WINTER WEATHER OR
FLASH FLOOD PRODUCTS AT THIS TIME.
FRIDAY AFTERNOON AND EVENING WILL BE A LULL IN THE ACTION WITH ONLY
SCATTERED SHOWERS EXPECTED ACROSS THE AREA. HOWEVER...BY LATE FRIDAY
NIGHT AND SATURDAY...A MORE POTENT STORM SYSTEM IS FORECAST TO ROLL
INTO THE AREA. 12Z GFS AND WRF BOTH INDICATE GOOD SOUTHERLY FLOW AND
DECENT PRECIPITABLE WATER AMOUNTS WITH THIS STORM ON SATURDAY AND
SATURDAY NIGHT WHICH SHOULD PRODUCE SOME PRETTY SIGNIFICANT
OROGRAPHIC RAINFALL. AT THIS TIME...RAIN WILL BECOME LIKELY DURING
THE DAY ON SATURDAY AND CONTINUE THROUGH SATURDAY NIGHT. PRELIMINARY
RAINFALL AMOUNTS WITH THIS SYSTEM WILL RANGE FROM 0.50" TO 1.50" FOR
COASTAL/VALLEY AREAS WITH 1.50" TO 2.50" IN THE FOOTHILLS AND
MOUNTAINS. SNOW LEVELS WILL REMAIN AROUND 6000 FEET ON
SATURDAY...THEN DROP TO AROUND 5500 FEET SATURDAY NIGHT.
LONG TERM...FOR THE EXTENDED...EXPECT SCATTERED SHOWERS ACROSS
THE AREA ON SUNDAY IN THE WAKE OF THE STORM WITH SNOW LEVELS
AROUND 5000 FEET.
FOR MONDAY THROUGH WEDNESDAY...MODELS HAVE THE SAME GENERAL IDEA
BUT DIFFER NOTICEABLY ON THE DETAILS. ESSENTIALLY...AN UPPER LEVEL
RIDGE IS FORECAST TO DEVELOP OVER THE WEST COAST. AT THIS TIME...
THE GFS IS MORE BULLISH WITH THE RIDGE THAN THE ECMWF. EITHER WAY
WILL EXPECT THIS PATTERN TO PRODUCE DRY CONDITIONS ACROSS THE AREA
WITH A GRADUAL WARMING TREND WITH AFTERNOON TEMPS NEAR SEASONAL
NORMS ON TUESDAY AND WEDNESDAY.
&&
.AVIATION...10/0006Z.
VFR CONDITIONS ARE EXPECTED THROUGHOUT AT LEAST 14Z TUESDAY...THEN
MVFR CONDITIONS IN RAIN WILL DEVELOP FROM NORTH TO SOUTH BETWEEN 14Z
AND THURSDAY EVENING. BEST CHANCES OF RAIN AND MVFR CATEGORY
CONDITIONS ON THURSDAY WILL EXIST NORTH OF KNTD.
KLAX AND KBUR...CEILINGS ABOVE 6000 FEET WILL PERSIST THROUGH AT
LEAST 14Z...BECOMING PREVALENT BY 20Z THURSDAY. THERE IS A 20
PERCENT CHANCE OF MVFR CONDITIONS AFTER 20Z. MVFR CONDITIONS IN RAIN
SHOULD DEVELOP BETWEEN 01Z AND 07Z THURSDAY NIGHT. NO WIND ISSUES
ARE EXPECTED THROUGHOUT THE PERIOD.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY (SEE LAXCFWLOX).
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).
HIGH RIP CURRENT RISK (SEE LAXSRFLOX).
&&
$$
SYNOPSIS...SETO/HALL
PUBLIC...HALL/THOMPSON
AVIATION...HALL
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