FXUS66 KLOX 070553
AFDLOX
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
950 PM PST SUN DEC 6 2009
...NEW AVIATION DISCUSSION...
.SYNOPSIS...A MOIST AND UNSTABLE AIR MASS WILL MOVE OVER THE
REGION THROUGH TUESDAY AS COLD LOW PRESSURE SYSTEM BRINGS
WINDS...RAIN...AND LOW ELEVATION SNOW TO THE AREA. A SERIES OF
STORM SYSTEMS WILL CONTINUE A WET AND UNSETTLED PATTERN
THROUGHOUT NEXT WEEKEND. TEMPERATURES WILL REMAIN WELL BELOW
SEASONAL NORMALS THROUGH THE WEEK...WITH THE COOLEST TEMPERATURES
OCCURRING MONDAY THROUGH WEDNESDAY MORNING.
&&
.UPDATE...HEALTHY VORTICITY MAXIMUM CAN BE SEEN AT 35N AND 136W
EMBEDDING INTO THE CYCLONIC FLOW PATTERN ALOFT. BOTH GFS AND NAM-
WRF SOLUTIONS AGREE THAT THIS FEATURE WILL BEGIN TO IMPACT THE
AREA BETWEEN 1 AM TONIGHT AND 4 AM TONIGHT. ISOLATED SHOWERY
CONDITIONS CURRENTLY THIS EVENING WILL BECOME MORE WIDESPREAD
THROUGHOUT TONIGHT AS THE VORT MAX KICKS EAST...WITH WIDESPREAD
RAIN LIKELY FILLING IN OVERNIGHT. AMSU TPW VALUES ARE ABOVE 1
INCH THIS EVENING NEAR 30N AND 130W...AND THIS FEATURE WILL LIKELY
INGEST SOME OF THE MORE MOIST SUBTROPICAL AIR MASS. A 70 KNOT 500
MB JET MAX WILL ACCOMPANY THE FEATURE TONIGHT...WITH WEAK COLD AIR
ADVECTION AT 500 MB DESTABILIZING THE MID-TO-UPPER LEVELS. AT 850
MB...A DECENT WARM AIR ADVECTIVE PATTERN WILL DEVELOP ALLOWING
OROGRAPHIC LIFT TO ASCEND THROUGHOUT THE LOWER-TO-MID LEVELS.
LATEST ACARS SOUNDING FROM KLAX AND KLGB INDICATE A CAP PRESENT
BETWEEN 825 AND 725 MB CURRENTLY...CAP WILL ERODE LATER TONIGHT AS
700 MB COLD AIR ADVECTION DEVELOPS...COOLING THE TOP OF THE
INVERSION...AND 850 MB WARM AIR ADVECTION...WARMING THE AREA
BELOW THE INVERSION. CURRENT ACARS SOUNDING ALSO INDICATE SNOW
LEVELS NEAR 4800 FEET THIS EVENING...RIGHT WHERE THE 0 DEGREE
CELSIUS WET BULB TEMPERATURE IS LOCATED. IF WET BULB ZERO
TEMPERATURES ARE INDICATIVE OF THE FREEZING LEVELS THIS
EVENING...THE FREEZING LEVEL SHOULD DROP AHEAD OF THE VORT MAX TO
BETWEEN 3000 AND 3500 FEET. INITIALLY...THIS WILL PRODUCE WINTRY
MIX DOWN TO AROUND THE 2500 FOOT LEVEL. THIS AGREES VERY WELL WITH
CURRENT PRODUCTS ISSUED.
BEST DYNAMICS ARE LOCATED WITH AN UPSTREAM VORT MAX NEAR 44N AND
140W. THIS FEATURE WILL SWING CYCLONICALLY AROUND THE TROUGH AND
SLAM INTO SOUTHERN CALIFORNIA ON MONDAY AFTERNOON. A 100 KNOT JET
MAX AT 500 MB CROSSES OVER LOS ANGELES COUNTY BETWEEN BETWEEN 1 PM
AND 4 PM MONDAY AFTERNOON. WITH VENTURA...SANTA BARBARA...AND SAN
LUIS OBISPO COUNTIES LYING IN THE MOST FAVORABLE JET
POSITION...THERE IS A CHANCE THAT THESE AREAS COULD GENERATE HIGH
PRECIPITATION TOTAL. THE WILD CARD SEEMS TO BE HOW MUCH OF THE
SUBTROPICAL PLUME IS PULLED INTO THE REGION. AT ANY RATE...THE
HEAVIEST RAINFALL AMOUNTS SHOULD STILL BE EXPECTED ON MONDAY
AFTERNOON.
&&
.PREV DISCUSSION... /ISSUED 236 PM PST SUN DEC 6 2009/
SHORT TERM...MONDAY NIGHT INTO TUE WILL ALSO BE FULL OF INTEREST.
IN ADDITION TO THE STRONG NORTHERLY WINDS...MOISTURE WILL BANK UP
ON THE NORTHERN MTNS AND FOOTHILLS. WITH SNOW LEVELS PLUMMETING
TO FAIRLY RARE LEVELS OF 2000 FEET AND BELOW...EVEN THE
ANTELOPE...SLO AND CUYAMA VALLEYS COULD WAKE UP TO A WHITE
TUESDAY. SNOW ADVISORIES MAY BE NEEDED FOR THOSE AREAS. THE REST
OF THE AREA WILL BE COLD...ESPECIALLY THE WIND SHELTERED AREAS
WHERE FROST AND FREEZE CONCERNS COULD POP UP. CLOUDS SHOULD BE
CLEARING OUT ON TUE...BUT WILL REMAIN QUITE COLD WITH THE
BITTERLY COLD AIR MASS. TUE NIGHT LOOKS EVEN COLDER AS THE WINDS
DIE AND THE SKIES CLEAR...AND MANY FREEZE WARNINGS/FROST
ADVISORIES ARE EXPECTED DURING THE COLDEST NIGHT OF THE SEASON.
MODELS CONTINUE TO SLOW DOWN AND WEAKEN THE NEXT SYSTEM...AS WED
DAY LOOKS TO STAY DRY BUT STILL COLD.
LONG TERM...THE NEXT SYSTEM NOW LOOKS TO PUSH IN WED NIGHT AND
THU...BUT MODELS CONTINUE TO TREND LESS AND LESS WITH THE PRECIP
AMOUNTS. THERE IS STILL A CONSIDERABLE AMOUNT OF UNCERTAINTY WITH
THE AMOUNTS AS A RESULT...BUT IT SHOULD RAIN AND IT WILL BE MUCH
WARMER WITH HIGHER SNOW LEVELS THAN MONDAYS SYSTEM. FRIDAY COULD
STILL SEE A SHOWER OR TWO...BUT LOOKS NOW TO BE THE BREAK BETWEEN
THE SECOND AND THIRD STORM. SAT IS LOOKING MORE AND MORE
INTERESTING...BUT STILL A BIT TOO EARLY TO GET TOO PRECISE ON.
OVERALL...NEXT WEEKEND LOOKS FAVORABLE FOR SOME MILD RAIN.
&&
.AVIATION...
07/0550Z.
CLOUDS WILL INCREASE AND LOWER OVERNIGHT. RAIN WILL OVERSPREAD THE
AREA TOWARDS DAWN AND LAST THROUGH THE DAY...TAPERING TO SHOWERS
DURING THE LATE AFTERNOON OR EARLY EVENING.
DURING THE RAIN CIGS AND VIS WILL VARY GREATLY BETWEEN IFR AND LOW
MVFR CONDS BUT FEW IF ANY LIFR CONDS ARE EXPECTED.
KLAX...LOW CONFIDENCE IN EXACT CIG/VIS FCST DURING THE RAIN AS BOTH
VALUES WILL CHANGE FROM ONE MOMENT TO THE NEXT. EXPECT IFR TO LOW
MVFR CONDS. EAST WINDS AROUND 10 KTS ARE LIKELY DURING THE MORNING
WITH A 30 PERCENT CHANCE OF ARRIVING BY 12Z.
KBUR...LOW CONFIDENCE IN EXACT CIG/VIS FCST DURING THE RAIN AS BOTH
VALUES WILL CHANGE FROM ONE MOMENT TO THE NEXT. EXPECT IFR TO LOW
MVFR CONDS. WINDS WILL ALSO VARY CONSIDERABLY FROM 14Z TO 02Z.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING (SEE LAXWSWLOX).
HIGH WIND WATCH (SEE LAXNPWLOX).
FLASH FLOOD WATCH (SEE LAXFFALOX).
GALE WATCH (SEE LAXMWWLOX).
HIGH RIP CURRENT RISK (SEE LAXSRFLOX).
MARINE WEATHER STATEMENT (SEE LAXMWSLOX).
SPECIAL WEATHER STATEMENT (SEE LAXSPSLOX).
COASTAL FLOOD STATEMENT (SEE LAXCFWLOX).
&&
$$
SYNOPSIS...HALL/HOFFER
PUBLIC...HALL/KITTELL
AVIATION...ASR
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