EXTREME SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSAN 855 PM PDT THU JUL 15 1999
...SYNOPSIS...
A TROUGH OF LOW PRESSURE OVER THE PACIFIC NORTHWEST WILL BRING DRY
SOUTHWEST FLOW ALOFT AND WEAK TO MODERATE ONSHORE LOW LEVEL FLOW TO
SOUTHERN CALIFORNIA THROUGH THE WEEKEND. WEST OF THE MOUNTAINS...
NIGHT AND MORNING LOW CLOUDS AND FOG ALONG THE COAST...EXTENDING
LOCALLY INTO THE INLAND VALLEYS...WILL CLEAR EACH MORNING. IN THE
MOUNTAINS AND DESERTS...ONLY A FEW AFTERNOON CLOUDS ARE EXPECTED
EACH DAY...WITH SEASONAL WARM TO HOT TEMPERATURES IN ALL AREAS.
...DISCUSSION...
NO UPDATES PLANNED AS CURRENT PACKAGE APPEARS TO BE ON TRACK.
AN UPR TROUGH OVR THE PAC NW WL WEAKEN DURG THE WEEKEND WITH DRY WK
SWLY FLOW ALF REMAINING OVR SRN CA THRU THE WEEKEND. HEIGHTS ALF AND
THICKNESSES LWR SLIGHTLY FRI...CHANGE LTL SAT...THEN BEGIN TO SLOWLY
BUILD SUN. WK TO MDT ONSHR LOW LVL FLOW WL CONTINUE THRU SUN WITH
CONDITIONS FAVORABLE FOR WK CSTL EDDY FORMATION EACH NIGHT. ALG THE
SRN CA CST...THE HEIGHT OF THE MARINE INVERSION BASE RANGED FM 1000
TO 1200 FT ALG THE CSTL PLAIN OF THE ORANGE AND LOS ANGELES CSTS PER HIGH
VERTICAL RESOLUTION ACARS SOUNDINGS FM LAX AND SNA...TO AROUND 1500
FT ALG THE SAN COUNTY CST PER THE 00Z NKX RAOB AND SFC REPORTS. THIS
IS SLIGHTLY DEEPER THAN 24 HOURS AGO WITH SOME SLIGHT ADDITIONAL
DEEPENING EXPECTED DURG THE NEXT 24 HOURS...LTL CHANGE FOR SAT...
THEN A SLOW DECR IN MARINE LYR DEPTH FOR SUN. DEPTH OF MARINE LYR
APPEARS MARGINAL FOR STRATUS TO REACH THE INLAND EMPIRE...BUT
CURRENT "PATCHY" WORDING FOR EARLY MORNING HOURS EACH DAY APPEARS
REASONABLE (I.E. ...LATE ARRIVAL...SHORT DURATION...LIMITED AREAL
EXTENT).
A FEW SHOWERS DEVELOPED OVR THE ERN SBD MTNS THIS ARTERNOON...
EVENTUALLY BECOMING THUNDERSTORMS AFTER DRIFTING NORTHEAST INTO THE
DESERT BETWEEN DAGGETT AND TWENTYNINE PALMS. BOTH THE K/F ETA AND
MAPS/RUC PICKED UP ON THIS DEVELOPMENT...SOMETHING THE OPERATIONAL
ETA WAS UNABLE TO DO. MDLS SHOW SOME ADDITIONAL DRYING OF THE MID
LVLS FOR FRI WHICH SHOULD FURTHER DECR AFTERNOON CONVECTIVE
DEVELOPMENT IN THE MTNS AND DESERTS.
AS THE UPR TROUGH ALG THE W CST WKNS DURG THE WEEKEND INTO EARLY
NEXT WEEK...SOME MID LVL MSTR MAY BEGIN TO SEEP BACK INTO SRN CA FM
THE E FOR AT LEAST SOME AFTERNOON CLOUDS OVR THE MTNS...IF NOT
ISOLATED AFTERNOON SHOWERS OR THUNDERSTORMS. HOWEVER...ALL EXTENDED
MDLS KP SUFFICIENT...THOUGH WK...UPR TROUGHING ALG THE W CST NEXT
WEEK TO KP SUCH MSTR RETURN AND ASSOCD CONVECTION MINIMAL FOR SRN
CA.
SAN 0000
.SAN...NONE.
MARTIN