Coastal Flood Statement 6, NWS Los Angeles, CA

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
830 PM PDT WED APR 25 2007

.SHORT TERM (TODAY-SAT)...WEAK UPPER LEVEL TROUGH OVER NORTHERN CALIFORNIA
WILL DIVE SOUTHEASTWARD OVERNIGHT WITH LOWERING HEIGHTS ACROSS THE
FORECAST AREA. WITH GALE FORCE WINDS IN PROGRESS ACROSS THE OUTER COASTAL
WATERS...APPEARS PROPER PARAMTERS ARE IN PLACE FOR AN EDDY CIRCULATION
TO DEVELOP OVERNIGHT AND THURSDAY MORNING ACROSS THE INNER COASTAL WATERS.
CURRENT SATELLITE IMAGERY SHOWING LOW CLOUDS AND FOG DEVELOPING THIS
EVENING OFF THE COAST OF SAN DIEGO COUNTY...BUT WE SHOULD SEE THESE LOW
CLOUDS EXPAND NORTHWARD WITH TIME OVERNIGHT. LATEST ACARS DATA SHOWS
MARINE LAYER DEPTH AROUND 800 FEET ACROSS LA BASIN...BUT THERE SHOULD
BE SOME DEEPENING TO AROUND 1500 FEET BY MORNING. WITH THIS IN MIND...
WE COULD SEE SOME PATCHY LOW CLOUDS AND FOG SPREAD INTO THE LOWER VALLEYS
AROUND SUNRISE.

PRESSURE GRADIENT BETWEEN SBA-SMX HAS TRENDED SHARPLY OFFSHORE WITHIN
THE LAST FEW HOURS...CURRENTLY AT -3.8 MB. WITH STRONG NORTHWEST WINDS
UPSTREAM...HAVE INCLUDED WINDS BELOW PASSES AND CANYONS OF SBA COUNTY
IN EVENING UPDATE...WHICH COULD LOCALLY GUSTS OVER 35 MPH. WINDS SHOULD
DIMINISH LATE TONIGHT AS EDDY INFLUENCE BEGINS TO DEVELOP. WITH A RETURN
OF MARINE LAYER PRESENCE ON THURSDAY AND MODERATE ONSHORE GRADIENTS...
THERE WILL LIKELY BE SOME COOLING ACROSS COASTAL AND COASTAL VALLEY
LOCATIONS. MEANWHILE INTERIOR TEMPERATURES WILL LIKELY BE AROUND PERSISTENCE
OR EVEN A FEW DEGREES WARMER IN SOME LOCATIONS ON THURSDAY.

*** FROM PREVIOUS DISCUSSION ***

HIGH PRESSURE WILL BUILD RAPIDLY THU NIGHT AND FRI, CAUSING DAYTIME
HIGHS TO INCREASE 10-15 DEGREES FRI AND SAT. WARMER VALLEY LOCATIONS
WILL REACH THE LOW TO MID 90S. MEANWHILE, WEAK ONSHORE FLOW WILL
PERSIST, KEEPING COASTAL TEMPS QUITE A BIT COOLER. NAM IS EVEN
SHOWING THE EDDY CIRCULATION CONTINUING RIGHT ON THROUGH SAT AM SO
IM NOT CONVINCED THAT CLOUDS WILL CLEAR COMPLETELY. THE INVERSION
WILL BE VERY STRONG AND LOW, MEANING DENSE FOG COULD BE A PROBLEM
FOR COASTAL AREAS FRI AND SAT.

.LONG TERM (SUN-WED)...WARMING TREND COMES TO AN END SAT. ECMWF AND
GFS IN GOOD AGREEMENT EARLY NEXT WEEK, SHOWING THE RIDGE BEING
REPLACED BY A FULL LATITUDE TROF ALONG THE WEST COAST. ALTHOUGH
THERE ISNT ENOUGH MOISTURE OR ENERGY TO WARRANT ANY POPS, THIS
PATTERN WILL RESULT IN A SIGNIFICANT COOLING TREND, WITH TEMPS
BOTTOMING OUT WED, GENERALLY IN THE 60S AT MOST LOWER ELEVATION
LOCATIONS.

&&

.AVIATION...AT 0330Z...OR 830 PM PDT...CURRENT SATELLITE IMAGERY
SHOWING LOW CLOUDS AND FOG DEVELOPING OFF THE COAST OF SAN DIEGO
COUNTY. WITH EDDY CIRCULATION EXPECTED TO DEVELOP OVERNIGHT...
SHOULD SEE LOW CLOUDS AND FOG SURE NORTHWARD ALONG THE COAST...THEN
SPREAD LOCALLY INTO THE COASTAL VALLEYS SHORTLY BEFORE SUNRISE.
AT THIS POINT...BEST ESTIMATES FOR INITIAL CEILINGS WOULD BE
600 TO 1000 FEET AT KLAX AND KLGB AROUND 09Z TO 11Z...THEN DEEPING
TO 1000 TO 1500 FEET ON THURSDAY MORNING. SOUTHEAST WINDS OF 4 TO
8 KNOTS CAN BE EXPECTED OVERNIGHT AND THURSDAY MORNING AT BOTH KLAX
AND KLGB DUE TO INFLUENCE OF EDDY CIRCULATION. AT THIS POINT...
THERE IS STILL SOME UNCERTAINTY OF LOW CLOUDS AND FOG SPREADING
INTO KBUR OR KVNY BUT WILL KEEP MENTION OF A CEILING IN BOTH LOCATIONS
FOR NOW.

.MARINE...GALE FORCE WINDS WILL CONTINUE ACROSS THE OUTER COASTAL WATERS
TONIGHT. THE STRONG WINDS COMBINED WITH A LARGE NORTHWEST SWELL WILL
RESULT IN COMBINED SEAS OF 12 TO 15 FEET WITH A PERIOD AROUND 17 SECONDS.
THIS HAS TRANSLATED INTO HIGH SURF CONDITIONS ALONG THE CENTRAL COAST
WHICH WILL LIKELY PERSIST THROUGH THURSDAY AFTERNOON. SOME OF THIS SWELL
ENERGY WILL MOVE INTO THE INNER COASTAL WATERS...CAUSING ABOVE NORMAL
SURF OF 4 TO 6 FEET ACROSS WEST FACING BEACHES OF LA AND VENTURA COUNTIES.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
GALE WARNING (SEE LAXCWFLOX).
SMALL CRAFT ADVISORY (SEE LAXCWFLOX).
HIGH SURF ADVISORY (SEE LAXCFWLOX).
HIGH RIP CURRENT RISK (SEE LAXSRFLOX).

&&

PUBLIC...GOMBERG/WOFFORD
AVIATION...GOMBERG

WWW.WEATHER.GOV/LOSANGELES