SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
230 PM PDT MON MAY 17 1999
LOW CLOUD AREA LURKING JUST OFF CENTRAL CST ATTM. SOME STRATUS MAY
DRIFT ONSHR INTO THE BEACHES OF WRN SBA AND SLO COUNTIES LATER THIS
AFTERNOON AND EVENING...BUT SHOULD PUSH INLAND WITH MORE VIGOR ALG
THE CENTRAL CST OVERNIGHT. PROFILERS AND ACARS DATA SHOW THAT WARMING
ON THE ORDER OF 6 TO 10 DEGREES CELSIUS HAS OCCURRED BETWEEN 1000 AND
4000 FEET SINCE SUNDAY. AS A RESULT...TEMPS WERE UP SHARPLY IN MOST
AREAS TODAY...WITH THE HIGHER VLYS AND LOWER MTN ELEVATIONS LEADING
THE WAY IN TEMPERATURE GAINS.
18Z ETA CONTS TO DEPICT WK EDDY CRCLN ACRS THE INNER WATERS THRU TUE
MORNING. THIS COULD BRING SOME LOW CLOUDS/FOG INTO CSTL PORTIONS OF
L.A. CNTY TONIGHT...BUT THE EDDY LOOKS TO BE QUITE WK...AND SHOULD
NOT SEND LOW CLOUDS MUCH N OF LAX...OR CAUSE APPRECIABLE DEEPENING
OF THE MARINE LAYER. LOW INVERSION AND WK ONSHR PUSH WL KEEP VLYS IN
THE CLR THRU TUE. INVERSION HGT...GRADS AND TRENDS ARE FAVORABLE FOR
THE DVLPMNT OF SOME LCLLY DENSE FOG ACRS CSTL AREAS OF L.A. CNTY AND
ALG THE CENTRAL CST TONIGHT/TUE A.M..
ALL MODELS ARE IN GOOD AGREEMENT THRU 48 HRS...SHOWING FLAT UPR RIDGE
OF TODAY GRADUALLY BEING REPLACED BY WK...FLAT TROUGH BY LATE TUE...
WITH WK BROAD TROFINESS CONTG ACRS SRN CA THRU WED. ONSHR FLOW WILL
BEGIN TO INCRS AGAIN TUE...WHICH SHOULD CAUSE SOME COOLING TUE...MOST
NOTICEABLE WITHIN A FEW MILES OF THE CST. WITH A SHALLOW MARINE LYR
AND LTL CHG IN H85 AND BOUNDARY LYR TEMPS...VLYS SHOULD STAY FAIRLY
WARM TUE...LOSING AT MOST A FEW DEGREES ON TEMPS REACHED TODAY. INCRSG
ONSHR FLOW AND GRADUAL DEEPENING OF MARINE LYR WILL CAUSE LOW CLDS TO
PENETRATE FARTHER INLAND AND POSSIBLY INTO THE VLYS TUE NIGHT AND
WED...WITH MORE WDSPRD COOLING OCCURRING AT THAT TIME.
AFTER 48 HRS...MEDIUM RANGE MODELS ARE IN SOME DISAGREEMENT WITH
THE DEVELOPMENT OF THE TROUGH OVER CA. WHILE ALL MODELS INDICATE
GENERAL TROFINESS CONTG THROUGH THE END OF THE WEEK...THEY DIFFER
SIGNIFICANTLY WITH THE AMOUNT OF AMPLIFICATION AND PROGRESSION.
THE MRF AND NOGAPS ARE MOST AGRESSIVE IN DEEPENING THE SYSTEM...
SHOWING THE DVLPMNT OF CUT OFF LOW OVR SERN CA BY THE END OF THE
WEEK. THIS SOLN IS SUPPORTED BY THE 12Z AVN. THE ECMWF AND UKMET
KEEP A WKR AND MORE PROGESSIVE LOOK TO THE TROUGH...BUT WL HAVE
TO WAIT AND SEE IF THEIR LATEST SOLNS TREND TOWARD THAT OF THE
MRF/NOGAPS. AT THE VERY LEAST...DEEPENING UPR TROUGH AND INCRSG
ONSHR FLOW WL LEAD TO A GRADUAL INCRS IN LOW CLD COVERAGE AND DEPTH...
AND COOLING ACRS THE FCST AREA LATER THIS WEEK. AT WORST...THE
SYSTEM COULD CAUSE SOME MSTR TO WRAP BACK INTO THE FCST AREA WITH
AN OUTSIDE CHANCE OF A FEW SHOWERS...MAINLY ACRS MTN AREAS...AT
THE TAIL END OF THE WEEK.
LAX 000. BRUNO
.LAX...SMALL CRAFT ADVISORY...SEE LAXCWFLAX.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
830 PM PDT MON MAY 17 1999
.OVERVIEW...FIRST FOR SOME OPTIMISM. WHILE DIFFERING IN THE DETAILS
ALL OF THE LONG RANGE MODELS ARE NOW FORECASTING A PATTERN CHANGE FRI
AND BEYOND AS THE LONG WAVE RIDGE ON THE EAST COAST RETROGRADES WWD
TO 120W. BEFORE THEN WRN WA WILL NEED TO CONTEND WITH MODERATE POST
FRONTAL ONSHORE FLOW TONIGHT AND TUE FOR COOL CONDITIONS AND SHOWER
ACTIVITY...ESPECIALLY COAST...NEAR THE CASCADES...AND OVER AN AREA OF
CONVERGENCE CENTRAL PGTSND. TUE NIGHT AND WED PROMISES BRIEF DRYING
AND WARMING WITH SHORT WAVE RIDGING AND LIGHT OFFSHORE SFC PRES
GRADIENTS. THE NEXT SHORT WAVE TROF THU APPEARS TO BE TAKING A
DIFFERENT TRACK THAN THE PREVIOUS ONES...IT DIGS SWD JUST OFF THE
COAST AS IT GETS CUT OFF FROM THE WESTERLIES. THIS WILL PRODUCE ONLY
A BRIEF SHOWER CHANCE THU AND THU NIGHT MAINLY ON THE COAST AND OVER
SRN PORTIONS OF THE WRN WA INTERIOR.
.SHORT TERM...AT 02Z AN INCREASINGLY ILL DEFINED SFC CDFNT EXTENDS
FROM THE OKANOGAN VALLEY SWWD TO KPDX. THE UPPER LEVEL FRONT SEEMS TO
BE OUTRACING THE SURFACE FEATURE PER SATELLITE IMAGERY. SATELLITE
IMAGERY AND OBSERVATIONS SHOW LEE SIDE DRYING NE OF OLYMPICS AND NRN
PGTSND...THIS IS CONSISTENT WITH 35-45 KT SWLY H85 FLOW AS SHOWN BY
ACARS SOUNDINGS. EXPECT ADDITIONAL SHOWER ACTIVITY THIS EVENING
EXCEPT VICINITY LEE LOW NE OF OLYMPICS...FOLLOWED BY CNTRL PGTSND
CONVERGENCE ZONE AND MAINLY OROGRAPHIC SHOWERS LATE TONIGHT AND TUE
AS NEAR GALE WLY FLOW GRADUALLY DEVELOPS STRAIT OF JUAN DE FUCA. WILL
CHANGE THE NATURE OF THE PRECIPITATION TO SHOWERS AND ADJUST POPS A
LITTLE DOWNWARD WITH POST FRONTAL CONDITIONS TONIGHT. WILL ALSO RAISE
SN LVLS IN MTNS 1KFT PER AIRCRAFT SOUNDINGS.
ALBRECHT
UIL 9611 SEA 761- OLM 761-
.KATX...VCP21/CSR21...OPERATIONAL.
.SEW...GALE WARNING STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY COAST.