EXTREME SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSAN 900 PM PDT SUN JUN 20 1999
...SYNOPSIS...
WEAK FLOW ALOFT WILL BRING ONLY SMALL CHANGES TO THE WEATHER THROUGH
MID-WEEK. A TROUGH MOVING BY TO OUR NORTH WILL BRING A SLIGHT
INCREASE IN THE MARINE LAYER DEPTH MONDAY WITH SLIGHT COOLING TO
SOME AREAS...MAINLY THE INLAND EMPIRE. THE ONSHORE FLOW WILL WEAKEN
SLIGHTLY TUESDAY AND ALLOW TEMPERATURES TO INCREASE A FEW DEGREES
WEST OF THE MOUNTAINS. HURRICANE ADRIAN AT 8 PM PDT WAS 941 NAUTICAL
MILES SSE OF SAN DIEGO. SUMMER WILL ARRIVE MONDAY AT 1249 PM PDT.
...DISCUSSION...
THE DESERTS HEATED UP A BIT MORE TODAY THAN SATURDAY...SO THE
ONSHORE PRESSURE GRADIENTS WERE STRONGER. THIS BROUGHT SOME COOLING
TO MOST OF WESTERN SAN DIEGO AND ORANGE COUNTIES. THE 00Z NKX
SOUNDING HAD SOME COOLING IN THE LOWEST ONE MILE BUT A SIMILAR
INVERSION HEIGHT FROM SATURDAY. ACARS SOUNDINGS FROM LAX/SAN TONIGHT
BASICALLY MIRROR THE NKX SOUNDING AS THEY SHOW A FAIRLY DEEP
AREA...FROM 1500 TO 4000 FEET ABOVE SEA LEVEL WHERE THE TEMPERATURE
INCREASES WITH HEIGHT. THIS WILL HELP THE INVERSION HEIGHT INCREASE
IN THE NEXT 24 HOURS...BUT THE DYNAMICS OF THE TROUGH GOING BY TO
THE NORTH PLUS A WEAK EDDY SHOULD HAVE ONLY MINOR IMPACT HERE...SO
THE INVERSION WILL PROBABLY GO UP BY ABOUT 500 FEET TO A NEW HEIGHT
OF AROUND 2000 FEET BY MONDAY AFTERNOON. THIS SHOULD BRING COOLING
TO THE INLAND EMPIRE AND WEST SLOPES OF THE MOUNTAINS. EVEN THE
DESERTS MIGHT SEE A BIT OF COOLING AS THE 00Z ETA/NGM HAVE DECREASES
IN 850MB TEMPS. CLOSER TO THE COAST...MOST OF THE COOLING HAS
ALREADY OCCURRED TODAY SO TEMPS SHOULD DECREASE ONLY VERY
SLIGHTLY...IF AT ALL.
ON TUESDAY...WE SHOULD SEE A SLIGHT INCREASE IN TEMPS AGAIN AS THE
ONSHORE PRESSURE GRADIENTS DECREASE AS THE PAC NW TROUGH DECAYS AS
IN MOVES INTO THE NORTHERN ROCKIES. A COUPLE DAYS OF PERSISTENCE
SHOULD OCCUR WED/THU AS THE FLOW WILL BE VERY WEAK ALOFT UNTIL
ANOTHER TROUGH DEVELOPS JUST TO OUR NORTH OVER THE WEEKEND. THE 12Z
ECM ACTUALLY HAS NO DECREASE IN HEIGHTS HERE THROUGH SATURDAY...SO
ONLY SLIGHT COOLING IS EXPECTED THEN WEST OF THE MOUNTAINS SINCE WE
WOULD LIKELY HAVE INCREASING COASTAL EDDIES AGAIN.
HURRICANE ADRIAN SHOULD HAVE NO IMPACT ON OUR WEATHER AS THERE IS A
POOL OF BELOW-NORMAL SSTS SOUTHWEST OF BAJA TO ACT AS A SHIELD. EVEN ITS
HIGH CLOUDS SHOULD REMAIN TO OUR SOUTHEAST AS THE FLOW ALOFT WILL BE
LIGHT AND GENERALLY TOO WESTERLY LATER THIS WEEK.
THE FORECAST WILL BE UPDATED SHORTLY AFTER 9 PM...MOSTLY FOR
TEMPERATURE ADJUSTMENTS.
SAN 0000
.SAN...NONE.
MAXWELL