FXUS66 KSGX 051153
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
350 AM PST SAT DEC 5 2009

.SYNOPSIS...UPPER LEVEL LOW PRESSURE APPROACHING FROM THE NORTH WILL 
BRING COOLING THROUGH THE WEEKEND. THIS LOW WILL MOVE ACROSS 
SOUTHERN CALIFORNIA EARLY NEXT WEEK BRINGING RAIN...MOUNTAIN SNOW 
AND STRONG WINDS MONDAY AND TUESDAY. A SECOND...WARMER STORM WILL 
BRING MORE RAIN THURSDAY AND FRIDAY. 

&&

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

LOW LEVEL MOISTURE RECOVERY HAS STARTED OVER ORANGE COUNTY WHERE 
DEWPOINTS WERE IN THE 40S AT 11Z. HOWEVER...DEWPOINTS WERE ONLY IN 
THE 20S AND 30S OVER COASTAL SAN DIEGO COUNTY...LIKELY DUE TO WEAK 
COLD AIR DRAINAGE WINDS KEEPING THE EXTENSIVE STRATUS DECK OVER THE 
COASTAL WATERS AT BAY. 

THE MARINE LAYER WILL DEEPEN RAPIDLY AND SPREAD INTO THE COASTAL 
ZONES TODAY...THEN INTO THE VALLEYS TONIGHT AHEAD OF A COLD UPPER 
LOW OVER THE PACIFIC NORTHWEST. THIS COLD LOW WILL SLIDE ACROSS 
SOUTHERN CALIFORNIA MONDAY AND MONDAY NIGHT. LIGHT SHOWERS MAY START 
AS EARLY AS SUNDAY AFTERNOON/EVENING...BUT THE BEST CHANCES FOR 
HEAVY PRECIPITATION WILL BE ON MONDAY WHEN THE HEART OF THE SYSTEM 
TRACKS OVERHEAD. THIS STORM IS STRONG ENOUGH...COLD ENOUGH AND WET 
ENOUGH TO HAVE SIGNIFICANT IMPACTS. STRONG WLY UPSLOPE FLOW AND 
ABUNDANT LOW LEVEL MOISTURE WILL BRING PERIODS OF HEAVY RAIN AND MTN 
SNOW. SNOW LEVELS WILL LOWER TO 4000 FEET ON MONDAY.  

PRELIMINARY RAINFALL TOTALS RANGE FROM ABOUT AN INCH TO AN INCH AND 
A HALF WEST OF THE MOUNTAINS AND NEAR HALF AN INCH IN THE DESERTS. 
WATER EQUIVALENT AMOUNTS IN THE MOUNTAINS SHOULD RANGE FROM ABOUT AN 
INCH AND A HALF TO THREE INCHES...TRANSLATING TO HEAVY SNOW 
ACCUMULATIONS OF A FOOT OR MORE AT THE HIGHER ELEVATIONS. DENSE FOG 
AND STRONG WINDS WILL IMPACT TRAVEL IN THE MOUNTAINS...AND WINTER 
STORM OR BLIZZARD WARNINGS WILL BE NEEDED IN THE MOUNTAINS AT THE 
TIME NEARS. 

MUDSLIDES AND DEBRIS FLOWS IN THE RECENTLY BURNED AREAS ARE A 
DISTINCT POSSIBILTY...AS IS FLOODING OF POORLY DRAINED STREETS AND 
LOW LYING AREAS. 

.LONG TERM (TUESDAY-FRIDAY)...A BRIEF RESPITE ARRIVES TUESDAY WITH A 
BIT OF A BREAK BEFORE THE NEXT STORM. ROUND TWO BEGINS THURSDAY AS A 
SECOND MOISTURE LADEN PACIFIC STORM WITH TROPICAL CONNECTIONS ROLLS 
ACROSS SOUTHERN CALIFORNIA. THIS WARM STORM WILL BRING ADDITIONAL 
HEAVY RAIN AND ALSO ELEVATE FLOOD CONCERNS FROM A POTENTIALLY RAPID 
SNOWMELT.  

&&

.AVIATION...
050830Z...HIGH CLOUDS WILL MOVE OVER THE AREA TODAY. THE MARINE 
LAYER IS EXPECTED TO BEGIN TO INCREASE THIS MORNING. STRATUS IS 
FORECAST DEVELOP ALONG THE COAST THIS MORNING AND MOVE INLAND 
AFTERNOON. AREAS OF FOG MAY DEVELOP EARLY THIS MORNING WITH VSBY 
3-5SM...LOCALLY 1-2SM AND ISOLATED 1/2SM OR LOWER. STRATUS BASES 
COULD BE AROUND 500 FT MSL EARLY AND THEN INCREASE THROUGH TODAY AS 
THE MARINE LAYER DEEPENS. BASES THIS AFTERNOON/EVENING EXPECTED TO 
BE AROUND 2500 TO 3000 FT MSL WITH VSBY MOSTLY ABOVE 7SM. DRIZZLE 
AND LIGHT RAIN MAY DEVELOP THIS AFTERNOON OR TONIGHT FROM THE 
DEEPENING MARINE LAYER AND CONTINUE THROUGH SUNDAY MORNING. 
SCATTERED TO BROKEN AREAS OF STRATUS EXPECTED SUNDAY AFTERNOON.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...

SPECIAL WEATHER STATEMENT...SEE LAXSPSSGX. 

EXTENDED HYDROLOGIC FORECAST...SEE LAXESFSGX.

&&

$$

PUBLIC...MOEDE  
AVIATION...WHITLOW