FXUS66 KSGX 281351 AAA
AFDSAN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN DIEGO
600 AM PST SAT FEB 28 2004

.SYNOPSIS...BUILDING HIGH PRESSURE BOTH AT THE SURFACE AND ALOFT 
WILL END THE SHOWERS THIS MORNING. DRY NORTHWEST FLOW ALOFT WILL 
CONTINUE FAIR WEATHER ON SUNDAY. HIGH PRESSURE WILL WEAKEN ON 
MONDAY. SHOWERS RETURN MONDAY NIGHT AND TUESDAY AS A COLD FRONT 
MOVES IN FROM THE NORTH FOLLOWED BY LOW PRESSURE ON TUESDAY. HIGH 
PRESSURE WILL REBUILD DURING THE SECOND HALF OF THE COMING WEEK FOR 
A RETURN TO FAIR WEATHER. 

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES.

.SHORT TERM...TROUGH AXIS IS EAST OF FORECAST AREA BUT UPSTREAM JET 
LEVEL WINDS COMPARED WITH THOSE DOWNSTREAM OF THE TROUGH ARE ABOUT 
50 KTS HIGHER WHICH IS SLOWING EASTWARD PROGRESS. SATELLITE WATER 
VAPOR IMAGERY SHOWED ONE LAST EMBEDDED IMPULSE...DROPPING SOUTH OFF 
THE COAST. AT 1030 UTC IT WAS OVER THE OUTER WATERS AND SHOULD MAKE 
THE TURN ACROSS NORTHERN BAJA CALIFORNIA IN THE NEXT FEW HOURS. THIS 
HAS ENHANCED SHOWER ACTIVITY AHEAD OF IT OVER FORECAST AREAS. 
HOWEVER EXPECT INCREASING SUBSIDENCE AND SHOWERS TO END BETWEEN 
SUNRISE AND MID MORNING. MODELS GENERALLY SUPPORT THIS IN SHOWING 
NEGATIVE VORTICITY ADVECTION/PREDOMINATE DOWNWARD VERTICAL VELOCITY 
AND SHRINKING MOISTURE LAYER IN LOW LEVELS AFTER 18Z. THUS HAVE  
LEFT A MENTION OF SHOWERS IN THE FIRST 6 HOURS OF THE FORECAST. THE 
ONLY OTHER LINGERING PROBLEM IS THE HIGH SURF. THE SMALL CRAFT 
ADVISORY WAS ALREADY DROPPED AND EXPECT TO CANCEL HIGH SURF ADVISORY 
AT 6 AM. IF SHOWERS HAVE NOT REDEVELOPED OVER WATER/COASTAL ZONES AT 
THAT TIME...MAY ELIMINATE THEM IN THE ZONE UPDATE AT THAT TIME.   
FOR THE REMAINDER OF TODAY THROUGH SUNDAY BUILDING HIGH 
PRESSURE...SURFACE AND ALOFT...COUPLED WITH MILD OFFSHORE 
FLOW...WILL PROVIDE CLEAR SKIES AND WARMER DAYTIME TEMPERATURES. 
ONLY OTHER SHORT TERM THREAT WORTH CONSIDERING IS FROST/FREEZE 
TONIGHT/SUNDAY NIGHT UNDER CLEAR SKIES AND DIMINISHING WINDS. 
MOS GUIDANCE IS STILL LATE FROM 28/00Z MODEL RUN. IF IT'S IN BEFORE 
0600 PST MAY REMATCH TEMP GRIDS AND INCLUDE CHANGES IN ZONE UPDATE.  

.MEDIUM RANGE...SAW THE 00Z EXTENDED PROGS, THEY ARE STILL IN 
AGREEMENT WITH EARLIER RUN ON TIMING OF OVERRUNNING PRECIPITATION 
REACHING SW SAN BERNARDINO COUNTY/ORANGE COUNTY MONDAY AFTERNOON 
WITH COLD FRONTAL PASSAGE ACROSS FORECAST AREA MONDAY NIGHT AND COLD 
UPPER LOW MOVING ACROSS SOUTHERN CALIFORNIA TUESDAY. MODIFIED POP 
GRIDS UPWARD FORM WHAT I HAD INHERITED OTHERWISE TREND OF FORECAST
OKAY. NEXT SHIFT MIGHT WANT TO JACK THEM UP SOME MORE. LEFT DAYS 5 
THROUGH 7 UNALTERED AS THERE IS SOME DISAGREEMENT BETWEEN THE MEDIUM 
RANG E MODELS ON WHETHER THE LOW WILL LEAVE A HANG BACK TROUGH OR A 
BROAD FLAT RIDGE WILL BUILD IN.  

&&

.SGX WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

BALFOUR