963 
FXUS66 KLOX 210545
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
945 PM PST FRI DEC 20 2002

MOIST ONSHORE FLOW KEEPING SCATTERED SHOWERS OVER SLO/SBA COUNTIES THIS
EVENING. OTHERWISE PLENTY OF HI CLOUDS MOVING INTO THE DISTRICT. AS THE
NEXT WEATHER DISTURBANCE APPROACHES THE CENTRAL COAST...SHOWERS SHOULD 
INCREASE IN COVERAGE OVER NORTHERN PARTS OF THE DISTRICT LATE TONIGHT. 
A FEW STRAY SHOWERS WILL BE POSSIBLE SOUTH OF POINT CONCEPTION LATER 
TONIGHT AS WELL.

SHORTWAVE UPPER TROF IS FORECAST TO MOVE INTO THE DISTRICT SAT
AFTERNOON. RAIN WILL SPREAD INTO THE CENTRAL COAST EARLY THEN DOWN
THROUGH L.A. COUNTY DURING THE AFTERNOON. POPS ARE PROBABLY TOO LOW FOR
VTU/L.A. COUNTIES FOR SAT AFTERNOON...AND WILL UPDATE THE ZONES TO
BOOST POPS THERE TO LIKELY. SURFACE LOW PRESSURE IS FORECAST TO DEVELOP
OFF THE COAST AND MOVE SOUTH OF THE DISTRICT BY SAT EVENING. THIS WILL 
ACTUALLY SET UP AN OFFSHORE FLOW ACROSS THE REGION WHICH SHOULD HELP TO 
DIMINISH SHOWERS OVER THE COAST AND VALLEYS...HOWEVER IN THE MOUNTAINS 
AND ANTELOPE VALLEY THE SHOWERS SHOULD LINGER. SNOW LEVELS MAY GET LOW
ENOUGH IN THE FOOTHILLS OF THE ANTELOPE VALLEY THAT SOME MEASURABLE
SNOW IS EXPECTED BY SUN MORNING MAINLY ABOVE 3500 FEET. THE MESO-ETA
HAS BROUGHT LESS QPF TO THE DISTRICT FROM PREVIOUS RUNS...WITH THE GFS
ABOUT THE SAME OR JUST A LITTLE MORE. ABOUT 1/2 TO ONE INCH OF RAIN
WILL BE POSSIBLE OVER MOST OF THE DISTRICT...ALTHOUGH THE MOUNTAINS
COULD GET A BIT MORE...BUT WINDS WITH THIS SYSTEM ARE MUCH WEAKER AND
OROGRAPHIC ENHANCEMENT WILL BE LESS THAN THE THU NITE SYSTEM. SNOW
LEVELS IN THE MOUNTAINS WILL BE DOWN TO ABOUT 4000 FEET. SNOW
ACCUMULATIONS FOR SAT THRU SAT NITE COULD BE OVER 6 INCHES IN THE 
HIGHER ELEVATIONS...AND SNOW ADVISORIES MAY BE NEEDED. 500 MB TEMPS ARE
FORECAST TO BE NEAR -28 DEG C...AND THE POSSIBILITY OF ISOLATED 
THUNDERSTORMS CANNOT BE RULED OUT AS WELL.

A LARGE UPPER TROF IS EXPECTED TO LINGER OVER THE SOUTHWESTERN U.S.
SUN THRU MON NITE BEFORE MOVING EAST ON TUE. OFFSHORE FLOW IS EXPECTED 
TO PERSIST OVER THE DISTRICT DURING THE PERIOD. UPSLOPE CLOUDS AND 
SHOWERS WILL BE POSSIBLE IN THE L.A./VTU MOUNTAINS AND ANTELOPE VALLEY
INTO SUN EVENING BEFORE SOME DRIER AIR STARTS TO FILTER IN. DRY BUT 
COOL WEATHER CAN BE EXPECTED MON. ANOTHER IN A SERIES OF SHORTWAVE
UPPER TROFS IS FORECAST TO MOVE INTO THE DISTRICT ON TUE...ALONG WITH 
ANOTHER ROUND OF RAIN AND MOUNTAIN SNOW. THE GFS FORECASTS THE SYSTEM
TO PUSH THRU TUE NITE...WITH DRY WEATHER RETURNING FOR CHRISTMAS DAY.
BELOW NORMAL TEMPS WILL CONTINUE THRU THE PERIOD.

LAX 2673. SIRARD

.LOX...SMALL CRAFT ADVISORY (SEE LAXCWFLOX).
       HIGH SURF ADVISORY (SEE LAXMWSLOX).