SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
900 AM PDT TUE MAY 11 1999
LOW CLOUDS AND PATCHY DENSE FOG FORMED OVER THE SANTA BARBARA COUNTY
CENTRAL COAST INTO THE SANTA YNEZ VALLEY THIS MORNING...BUT SHOULD
BURN OFF BY 10 AM. LOW CLOUDS AND PATCHY FOG WERE NOTED OVER PARTS OF
LAX COUNTY OVER COASTAL AREAS AND INTO THE SAN GABRIEL VALLEY. USC
PROFILER SUGGESTS A MARINE LAYER ABOUT 2400 FEET WITH LIGHT SOUTHEAST
FLOW IN THE MARINE LAYER AND NORTHERLY FLOW ABOVE IT. ACARS DATA AT
LAX CONFIRMS THIS. NOT A CLASSIC EDDY CIRCULATION BUT ENOUGH OF A
BROAD SELY FLOW TO CARRY LOW CLOUDS UP THE COAST TO NEAR THE S COAST
OF SBA COUNTY. THIS FLOW SHOULD TURN ONSHORE THIS AFTERNOON WITH MUCH
OF THE CLOUDINESS BURNING OFF. HAVE UPDATED ZONES TWICE THIS MORNING
FOR THE LOW CLOUDS. ON THE LATEST UPDATE AT 825 AM WENT AHEAD AND
TWEAKED TEMPS DOWN A FEW DEGREES OVER LAX COUNTY SINCE MARINE LAYER IS
HANGING TOUGH.
12Z NGM/ETA IN. BOTH IN GENERAL AGREEMENT WITH 500 MB HEIGHTS
INCREASING OVER SOCAL THRU WED THEN A BROAD UPPER TROF STARTS TO MOVE
INTO CA WED NITE. BOTH MODELS ALSO SHOW MODERATE ONSHORE GRADIENTS
THIS AFTERNOON WITH EVEN STRONGER WESTERLY AFTERNOON GRADIENTS WED
AFTERNOON...ESPECIALLY OVER SLO/SBA COUNTIES. ONE PROBLEM OF THE DAY
WILL BE HOW QUICKLY THE MARINE LAYER SHRINKS THRU WED THEN INCREASES
BY THU AND HOW THIS COMBINED WITH THE ONSHORE FLOW WILL AFFECT HI
TEMPS. ANOTHER CONSIDERATION IS DETERMINING EXTENT OF LOW CLOUDS
TONIGHT AND WEDNESDAY NIGHT. THE ETA SUGGESTS A WEAK EDDY IN THE SEA
LEVEL PRESSURE FIELDS LATER TONIGHT ALTHO THE 30AGL WINDS DO NOT SHOW
A CIRCULATION. SOME ONSHORE GRADIENTS PERSIST WED NITE AS WELL. A
THIRD PROBLEM TO CONSIDER IS HOW STRONG WITH WINDS WILL GET WED
AFTERNOON WITH THAT GOOD ONSHORE GRADIENT. WILL LOOK AT OTHER MODEL
DATA...INCLUDING THE AVN AND MESO-ETA...TO MAKE DECISIONS ON THESE FOR
THE AFTERNOON ZONE PACKAGE.
LAX 000. SIRARD.
.LAX...SMALL CRAFT ADVISORY...SEE LAXCWFLAX.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
207 AM PDT TUE MAY 11 1999
AVN WELL INITIALIZED PER IR/ACARS/UA DATA WITH OCFNT CONTINUING TO
STRETCH ALG 133W. ELONGATED TROF BASE BTWN 130-150W...WITH DIFLUENCE
ALG W CST DRYING PCPN FIELDS A TAD. SPEED MAX ENTERING PIC FM SW
SHOWING 3-5C COOLING OF TOPS IN PAST 2 HRS JUST E OF TRIPLE POINT
(45N 131W AT 09Z)...YET COOLING ONLY TEMPORARY. AS SUSPECTED LAST
NIGHT THE MAIN ENERGY ASSOCD WITH THIS LOW GOING S INTO CA/OR WITH
WEAKER DYNAMICS OVR WA AFTER INTIAL SURGE. AMS MOST UNSTBL OVR WA TUE
NIGHT INTO WED MORNING...WITH RATE OF COOLING ALF LARGEST AND IN THE
L EXIT REGION OF 120KT JET. THANKS STEVE FOR POINTING OUT THE GREY VS
RED TROF TOPS! HOWEVER MICROSCALE FEATURES TO CONSIDER. WITH 25KT+
AT 85/70H XPCT TO SEE BOTH THE PGTSND CONV ZONE AND LEE TROF E OF
OLYMPICS TUE NIGHT AND WED WITH ISOLD TS IN BOTH. PER MTN
SNOWS...HEALTHY FLOW PLUS PCPN TO WARRENT SNOW ADVISORY THUS ISSUING
WITH PACKAGE.
.EXTENDED...JET SAGS S INTO OR/CA WED NIGHT THRU FRI...AS CENTER OF
UPR LOW SAGS SE OVR WA WITH MINIMAL VERTICAL MOTION. ALL THIS WASHES
OUT AS SHOWERS...WITH MTN SNOWS. SFC FLOW DMSHG THUS PGTSND CONV
ZONE AND LEE LOW TO FIZZLE WED NIGHT.
.LONGER RANGE EXTENDED...CONSISTENCY IN MRF OVER PAST 4 NIGHTS
TOTALLY A DELIGHT AND ENHANCING CONFIDENCES AS RIDGE OVER ALASKA
CREEPS W INTO SIBERIA...RESULTING IN DEEP ALEUTIAN LOW AND ITS
AMPLIFICATION OF THE RIDGE ALG THE W COAST FOR THE WEEKEND AND INTO
NEXT WEEK! IS IT TIME TO SAY GOOD BYE TO BELOW NORMAL TEMPS??? :)
QUERCIAGROSSA
UIL 987 SEA 987 OLM 977
.KATX...VCP31/CSR31...OPERATIONAL...
.SEW...SCA COAST...
GALE CENTRAL AND EASTERN STRAIT...