EXTREME SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSAN 310 AM PDT THU SEP 16 1999
...SYNOPSIS...
A WEAK UPPER TROUGH WILL REMAIN ALONG THE CALIFORNIA COAST THROUGH
THE WEEKEND WITH DRY SOUTHWESTERLY FLOW ALOFT AND WEAK ONSHORE LOW
LEVEL FLOW FOR SOUTHERN CALIFORNIA. SEASONAL TEMPERATURES WILL
CONTINUE INLAND WITH BELOW NORMAL TEMPERATURES NEAR THE COAST. NIGHT
AND MORNING COASTAL LOW CLOUDS WILL EXTEND LOCALLY INTO THE INLAND
VALLEYS.
...DISCUSSION...
A WEAK UPPER TROUGH WILL CONTINUE ALG THE CA CST THRU THE WEEKEND
WITH MDL DIFFERENCES IN TIMING OF WK SHORTWAVES MOVG THRU THE MEAN
TROUGH POSITION. FOR SRN CA...DRY SWLY FLOW ALF WL CONTINUE WITH WK
ONSHR LOW LVL FLOW. ETA INITIALIZED BEST THE WK SHORTWAVE EVIDENT IN
WATER VAPOR IMAGERY OVR THE CSTL WATERS S OF POINT CONCEPTION. THE
ETA MOVES THIS SHORTWAVE EAST SOUTHEASTWARD WITH THE SHORTWAVE WKNG
AND TRACKING ACROSS EXTREME NRN BAJA THIS AFTERNOON. A CYCLONIC
CRCLN CONTINUES TO BE CENTERED OVR THE SRN CA CSTL WTRS AT LWR LVLS
JUST ABV THE SFC WITH ACARS SOUNDINGS AT LGB/SNA/ONT SHOWING
CONTINUED ELY-NELY FLOW OF 20 TO 30 KT ABV THE MARINE INVERSION UP
TO AROUND 700 MB. THIS ELY FLOW ABV THE MARINE INVERSION...AT LEAST
IN PART...SEEMS TO BE RESPONSIBLE FOR THE SLOW RETURN OF STRATUS TO
SRN CSTL SXNS WITH MOST STRATUS IN SRN SXNS STILL ALG AND W OF THE
OFSHR ISLANDS. WL REMOVE STRATUS FM INLAND EMPIRE AND TRIM BACK
WORDING FOR REMAINING CSTL AREAS THIS MORNING. ALSO ADDED LCL NELY
WINDS TODAY FOR THE APPLE AND YUCCA VLYS AND ADJ MTNS AS SOME OF THE
NELY WINDS ALF SHOULD SFC LATE THIS MORNING AND AFTERNOON...NOT
UNLIKE WHAT OCCURRED TUE WED AFTERNOON IN HIGH DESERT LOCATIONS SUCH
AS DAG AND PMD. 00Z COMAPS SHOWS CYCLONIC CRCLN AT 925 MB PERSISTING
OVR THE CSTL WTRS THROUGH TONIGHT...BUT EXTENDING ONLY LCLLY...AT
MOST...TO THE SFC (I.E. LTL CHANGE FM PRESENT). WL USE GENERIC
"AREAS" WORDING FOR CSTL STRATUS W OF MTNS AND KP OUT OF INLAND
EMPIRE DUE TO ELY FLOW ALF. WL LET LATER SHIFTS FINE TUNE OR ADD
DETAIL AS APPROPRIATE.
EXTENDED...BY EARLY NEXT WEEK...MDLS DEVELOP A LARGE UPR CUTOFF LOW
OVR THE NRN AND CNTRL PLAINS WITH THE WLYS DISPLACED WELL TO THE N
ACROSS SRN CANADA. A WK UPR LOW WL REMAIN ALG THE CA CST WITH ONLY
MINOR DAY TO DAY VARIATIONS IN THE WEATHER FOR SRN CA THRU THE
MIDDLE OF NEXT WEEK.
SAN 000
.SAN...NONE.
MARTIN