EXTREME SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSAN 145 PM PDT FRI JUL 30 1999
...SYNOPSIS...
ONSHORE FLOW AND A REDEVELOPING MARINE LAYER WILL BRING INCREASING
COASTAL NIGHT AND MORNING LOW CLOUDS AND A SLIGHT COOLING TREND
THERE THROUGH SUNDAY. OTHERWISE...DRY SOUTHWEST FLOW ALOFT WILL KEEP
THE WEATHER FAIR.
...DISCUSSION...
A MINOR COASTAL EDDY OCCURRED THIS MORNING AND BROUGHT SOUTH WINDS
TO LINDBERGH FIELD. IT HAD NO EFFECT ON THE INVERSION HEIGHT. LOW
CLOUD COVERAGE WAS SIMILAR TO THAT ON THURSDAY MORNING...BUT THERE
WAS SLIGHTLY MORE FOG. THE 00Z COAMPS DID A GREAT JOB AT DEPICTING
THE EDDY DESPITE THE FACT THAT IT WAS WEAK...AND THE 12Z COAMPS
PREDICTS ANOTHER EDDY FOR TONIGHT/EARLY SATURDAY OF SIMILAR
INTENSITY...WHICH I BELIEVE.
THE FORECAST IS MOSTLY PERSISTENCE...THOUGH TEMPS MAY TREND DOWN A
BIT WEST OF THE MOUNTAINS DUE TO A TREND TOWARDS MORE CYCLONIC FLOW
AND VERY SLIGHT INCREASE IN THE MARINE LAYER DEPTH. ACARS
SOUNDINGS...AT LEAST OUT OF LA...STILL SHOW OUR MARINE LAYER DEPTH
AT OR SLIGHTLY ABOVE 1000 FEET. OUR SST VALUES NEAR THE BEACHES ARE
IN THE LOWER 60S...SO THAT WILL NOT HELP TEMPS ANY IN THE UPWARD
DIRECTION. THE ONSHORE FLOW HAS INCREASED BY 2-3 MB TO OUR
DESERTS...BUT THE MODELS INDICATE FUTURE INCREASES TO BE SMALL.
LOOKING AT THE BIGGER PICTURE...THE LOW WELL WEST OF SAN FRANCISCO
WILL REMAIN FAIRLY STATIONARY UNTIL IT LIFTS OUT EARLY NEXT WEEK.
THE HIGH ALOFT OVER THE CENTRAL US PRODUCING THE HEAT WAVE THERE
WILL GRADUALLY TRANSLATE WEST INTO THE INTERMOUNTAIN WEST.
HOWEVER...THE HIGH EXTENDS FAR ENOUGH SOUTH INTO MEXICO THAT THE
EASTERLIES OVER MEXICO ARE WEAK AND SHOULD CONTINUE TO BE SO UNTIL
AROUND TUE/WED OF NEXT WEEK. THUS...AT LEAST UNTIL THEN OUR
MTNS/DESERTS SHOULD BE FREE OF THUNDERSTORMS. BY THAT TIME OUR FLOW
ON THE AVN/MRF IS MORE SOUTHERLY AND RH VALUES MOST CERTAINLY WILL
INCREASE JUST TO OUR EAST OVER THE COLORADO RIVER VALLEY...BUT HERE
THE RH VALUES LOOK SOMEWHAT MARGINAL. THE ECM KEEPS US UNDER DRIER
SOUTHWEST FLOW AS EVERYTHING IS SHIFTED A BIT SOUTH.
SAN 0000
.SAN...NONE.
MAXWELL