FXUS66 KSGX 102213 RRA
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
230 PM PST THU DEC 10 2009

.SYNOPSIS...PARTLY CLOUDY AND COOL THE REST OF TODAY. THERE IS A 
CHANCE OF SHOWERS AND POSSIBLY A THUNDERSTORM LATE TONIGHT AND 
FRIDAY. MOIST WEST FLOW WILL CONTINUE THE CHANCE FOR SHOWERS 
SATURDAY MORNING...MAINLY INLAND. ANOTHER STORM SYSTEM WILL MOVE 
THROUGH SOUTHERN CALIFORNIA LATE SATURDAY AND SUNDAY...BRINGING 
MODERATE TO LOCALLY HEAVY RAIN AND MOUNTAIN SNOW. FAIR AND WARMER 
FOR THE BEGINNING OF NEXT WEEK AS HIGH PRESSURE ALOFT REBUILDS.

&&

.DISCUSSION...FOR SOUTHWEST CALIFORNIA INCLUDING SAN DIEGO... 
ORANGE...SOUTHWEST SAN BERNARDINO AND WEST RIVERSIDE COUNTIES.

MOSTLY CLEAR THIS AFTERNOON WITH HIGH CLOUDS BEGINNING TO INCREASE 
FROM THE WEST. THE NEXT SYSTEM IS SET TO AFFECT SOUTHERN CALIFORNIA 
VERY LATE TONIGHT AND FRIDAY WITH GENERALLY LIGHT RAIN. AS OF 1 PM 
THIS AFTERNOON...THE SYSTEM WAS LOCATED ABOUT 350 MILES OFFSHORE. 
THE LOW LEVELS WILL REMAIN FAIRLY DRY THROUGH FRIDAY MORNING DUE TO 
WEAK EASTERLY FLOW...HOWEVER INCREASING WARM/MOIST AIR ADVECTION 
ABOVE THE BOUNDARY LAYER WILL CAUSE LIGHT TO LOCALLY MODERATE 
RAINFALL IN THE MORNING. DIFFERENTIAL TEMPERATURE ADVECTION ABOVE 
THE BOUNDARY LAYER COULD WORK TO DESTABILIZE THE ATMOSPHERE...AND 
MODEL POINT SOUNDINGS INDICATE THAT 850 MB PARCELS BECOME WEAKLY 
UNSTABLE BY 09Z OVER SAN DIEGO. IN FACT...SATELLITE IMAGERY AND LONG 
RANGE LIGHTNING OBSERVATIONS ARE DETECTING THUNDERSTORMS ABOUT 500 
NM WSW OF SAN DIEGO WITH THIS SYSTEM. ADDED A SLIGHT CHANCE OF 
THUNDERSTORMS TO THE FORECAST FOR THE MORNING HOURS IN SAN DIEGO 
COUNTY. THE CURRENT FORECAST IS FOR ABOUT 1/4 INCH WEST OF THE 
MOUNTAINS AND 1/2 INCH IN THE MOUNTAINS...LOCALLY HEAVIER AMOUNTS IN 
AREAS WHERE CONVECTION OCCURS. GENERALLY DRY BY FRIDAY AFTERNOON 
WITH ONLY A FEW LINGERING SHOWERS INLAND NEAR THE COASTAL SLOPES. AS 
FOR SNOW...WARM AIR ADVECTION WILL LIFT THE SNOW LEVEL TO AROUND 
7000 FT OR MORE ON FRIDAY. A RAIN/SNOW MIX IS LIKELY AT RESORT 
LEVELS IN THE SAN BERNARDINO MOUNTAINS. RAIN AT IDYLLWILD AND IN THE 
SAN DIEGO MOUNTAINS.

ANOTHER PERIOD OF LIGHT TO MODERATE RAIN IS POSSIBLE ON SATURDAY 
MORNING...WITH ONE FINAL ROUND OF MODERATE TO LOCALLY HEAVY RAIN AND 
SNOW LATE SATURDAY INTO SUNDAY MORNING. IN BETWEEN EACH ROUND OF 
PRECIP...LIGHT SHOWERS MAY LINGER NEAR THE FOOTHILLS AND MOUNTAINS 
WHILE THE COAST EXPERIENCE PARTIAL CLEARING AND DRYING. SNOW LEVELS 
SHOULD FALL TO AROUND 5500 FEET OVER THE SAN BERNARDINOS AND 6500 
FEET OVER THE SAN JACINTOS BY SUNDAY MORNING.

THE TOTAL RAINFALL FOR FRIDAY THROUGH SUNDAY SHOULD GENERALLY BE IN 
THE RANGE OF 0.75 TO 1.75 INCHES FOR THE COAST AND VALLEYS...AND 
2.00 TO LOCALLY 4.00 INCHES ON THE FOOTHILLS AND COASTAL SLOPES OF 
THE MOUNTAINS. THE BIGGEST TOTALS SHOULD BE IN THE SAN BERNARDINO 
MOUNTAINS.

...FROM PREVIOUS DISCUSSION...
MEDIUM RANGE MODELS INDICATE SOME RIDGING EARLY NEXT WEEK WITH THE 
ECMWF INDICATING RIDGING DOMINATING THROUGH MOST OF NEXT WEEK. THE 
00Z GFS WANTS TO DEVELOP A REX BLOCK ALONG THE WEST COAST BY MID 
WEEK WITH THE ANCHOR LOW NEAR SOUTHERN CALIFORNIA. THE ECMWF WOULD 
INDICATE DRY THROUGH MOST OF THE WEEK WHILE THE GFS WOULD INDICATE 
SOME UNSETTLED CONDITIONS FOR SOUTHERN CALIFORNIA LATE IN THE WEEK. 
THE ECMWF HAS BEEN THE MODEL OF CHOICE IN THE RECENT PAST SO WILL 
LEAN TOWARD THIS MODEL.

&&

.AVIATION...
102112Z...SCATTERED CIRRUS WILL GRADUALLY THICKEN AND LOWER THIS 
EVENING...OTHERWISE VFR. CIGS WILL LOWER AFTER 06Z NEAR KSNA TO 
BELOW FL100...THEN TO AROUND FL025 AFTER 10Z WITH SHOWERS BECOMING 
LIKELY. ISOLATED CBS ARE POSSIBLE WITH VIS BRIEFLY 2SM OR LOWER IN 
+SHRA. FARTHER SOUTH NEAR KSAN...EXPECT MVFR CIGS AND SHOWERS BY 
AROUND 12Z FRI. CLOUDS WILL BE LAYERED TO AROUND FL150 WITH EMBEDDED 
CBS. MVFR CIGS AND PERIODS OF SHRA/-SHRA LIKELY MUCH OF THE DAY FRI. 
HIGHER TERRAIN WILL BECOME OBSCURED AFTER 12Z FRI.

&&

.MARINE...
A LONG PERIOD...6-8 FT W-NW SWELL WILL IMPACT THE BEACHES THROUGH 
FRIDAY WITH SURF 5 TO 8 FEET AND SETS UP TO 10 FEET. SURF HAS BEEN 
SLOW TO COME UP...BUT THE OUTER BUOYS INDICATE 7 TO 8 FEET AT 16 
SECONDS SO HIGH SURF SHOULD MATERIALIZE LATER TODAY OR THIS EVENING. 
A HIGH SURF ADVISORY IS IN EFFECT THROUGH FRI. THE HIGH SURF WILL 
ALSO GENERATE STRONG RIP CURRENTS. SURF AND SWELLS WILL LOWER WITH 
MAXIMUM SURF SETS NEAR 7 FEET AND MAXIMUM SWELLS TO AROUND 5 FEET BY 
FRIDAY AFTERNOON. 

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY...SEE LAXCFWSGX.
HYDROLOGIC OUTLOOK...SEE LAXESFSGX.

&&

$$

PUBLIC...SCV
AVIATION/MARINE...JAD