EXTREME SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSAN 300 AM PDT THU AUG 5 1999
...SYNOPSIS...
AN UPPER LEVEL LOW OFF THE PACIFIC NORTHWEST COAST WILL MOVE TO THE
NORTHERN CALIFORNIA COAST TODAY...THEN REMAIN NEARLY STATIONARY AND
SLOWLY WEAKEN THROUGH SATURDAY. SOUTHWEST FLOW ALOFT WILL CONTINUE
ACROSS SOUTHERN CALIFORNIA WITH MODERATE ONSHORE LOW LEVEL FLOW AND
A COASTAL EDDY WEAKENING FRIDAY AND SATURDAY. COOLING THAT BEGAN AT
THE COAST WEDNESDAY WILL EXTEND INLAND TODAY...WITH A SLOW WARMING
TREND DEVELOPING FOR FRIDAY AND SATURDAY.
...DISCUSSION...
00Z MDLS ARE CONSISTENT IN MOVG THE CLOSED LOW OFF THE PAC NW CST TO
A POSITION OFF THE NRN CA CST LATE THIS AFTERNOON...WITH THE UPR LOW
THEN REMAINING CNTRD ALG THE NRN CA CST THRU SAT. HEIGHT FALLS OVR
SRN CA ARE GREATEST DURG THE FIRST 24 HOURS...CHANGE LTL FOR FRI...
THEN REBUILD SLOWLY ON SAT AS THE UPR LOW ALG THE NRN CA CST SLOWLY
FILLS AND THE UPR RDG ACROSS THE SRN TIER OF STATES BEGINS TO BUILD
BACK SLOWLY TO THE W. SWLY FLOW ALF SHOULD CONTINUE THRU SAT WITH
THE SLY FLOW BLO 500 MB OVR THE LOWER DESERTS DEVELOPING A GREATER
WLY COMPONENT ON FRI FOR DRYING OF THE SHALLOW MID LVL MSTR OVR THE
DESERTS. ONSHR LOW LVL FLOW WL PK THIS AFTERNOON AND EVENING...THEN
SLOWLY WKN FRI AND SAT. THERE IS STILL SYNOPTIC SUPPORT FOR A WK
CSTL EDDY TONIGHT/FRI MORNING...THEN JUST WK ONSHR FLOW FOR FRI
NIGHT/SAT MORNING.
EVENING ACARS SOUNDINGS FM LAX/ONT/SAN SHOWED QUITE A GRADIENT IN
MID LVL MSTR AND WIND FLOW WITH A SOUNDING WITH MSTR FM LAX SHOWING
WLY TO SWLY FLOW AT ALL LVLS AND A DRY ATMOS ABV A MARINE INVERSION
BASE OF AROUND 1000 FT. IN CONTRAST...A SOUNDING WITH MSTR FM ONT
SHOWED A SHALLOW MOIST LYR OF ABOUT 75 MB AROUND THE 600 MB LVL WITH
SELY FLOW FM BLO 700 MB TO ABV 600 MB. A SOUNDING WITH MSTR FM SAN
SHOWED SWLY FLOW AT ALL LVLS ABV THE MARINE INVERSION WITH ONLY A
HINT OF MSTR NR 650 MB. EARLY WED EVENING THE INVERSION BASE WAS BR
1000 FT LAX...AND AROUND 1500 FT POINTS VLYS E AND CSTL SXNS S. WITH
GRADUAL HEIGHT FALLS ASSOCD WITH THE UPR LOW MOVG S ALG THE PAC NW
CST TO THE NRN CA CST AND A PERSISTENT CSTL EDDY...THE MARINE LYR
SHOULD DEEPEN TO AROUND 2000 FT BY MID MORNING TODAY. LTL CHANGE
IN MARINE LYR DEPTH FOR THU NIGHT/FRI MORNING...THEN A DECR IN DEPTH
AND EXTENT OF CSTL LOW CLOUDS FOR FRI NIGHT/SAT MORNING.
SAN 000
.SAN...NONE.
MARTIN