EXTREME SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSAN 945 PM PST WED MAR 22 2000
...SYNOPSIS...
INCREASING ONSHORE FLOW AND A DEEPENING MARINE LAYER WILL BRING A
RETURN OF COASTAL LOW CLOUDS AND A COOLING TREND TO SOUTHWEST
CALIFORNIA THROUGH FRIDAY. A GULF OF ALASKA STORM WILL MOVE INTO
SOUTHERN CALIFORNIA SATURDAY AND SUNDAY BRINGING SHOWERS...COOLER
TEMPERATURES...AND A CHANCE FOR THUNDERSTORMS TO SOUTHWEST
CALIFORNIA.
...DISCUSSION...
IN THE NEAR TERM...RUC IS FORECASTING A CSTL EDDY TO DEVELOP LATE
TONIGHT...DECAYING THU MORNING. SYNOPTIC PATTERN WITH PROGRESSION OF
A PAC SHORTWAVE INLAND INTO THE PAC NW SUPPORTS THIS SCENARIO. EARLY
EVENING ACARS SOUNDINGS SHOW THE BASE OF THE MARINE INVERSION AOB
1000 FEET MSL. WITH HEIGHTS ALF CHANGING LTL OVERNIGHT OR LWRG ONLY
SLIGHTLY...NOT MUCH DEEPENING OF THE MARINE LYR IS EXPECTED. THIS
SUPPORTS POTENTIAL FOR LCLLY DENSE FOG ALG THE CST LATE TONIGHT INTO
THU MORNING. EXPECT GREATEST COVERAGE OF LOW CLOUDS OVR NRN ORANGE
COUNTY AND SRN LOS ANGELES COUNTY PER 18Z ETA LOW LVL (975 MB) RH
PROGS. SOME ADDITIONAL DEEPENING OF MARINE LYR THU NIGHT AND FRI AS
HEIGHTS GRADUALLY LWR AND ONSHR FLOW INCREASES. EARLIER FORECAST MAY
HAVE BEEN A LTL AGGRESSIVE WITH THE DEGREE OF DEEPENING FOR THU
NIGHT THRU FRI MORNING. MORE SUBSTANTIAL DEEPENING IS POSSIBLE FRI
NIGHT THRU SAT MORNING AS THE WEEKEND GULF OF AK STORM APPROACHES.
IN THE EXTENDED...NEW AVN IN GOOD AGREEMENT WITH PREVIOUS MRF.
ECMWF IS TRENDING A LTL FARTHER W WITH CLOSED UPR LOW FOR THE
WEEKEND...SIMILAR TO THE MRF. RAIN SHOULD SPREAD INTO SW CA DURG THE
DAY SAT WITH SHOWERS TO CONTINUE INTO SUN. IT IS WORTH NOTING THAT A
PERFECT PROG AVN WOULD BE VERY CLOSE TO THE SYNOPTIC PATTERN
FAVORABLE FOR WATERSPOUT DEVELOPMENT OVR THE SRN CA CSTL WTRS SAT
AFTERNOON AND EVENING. AS THE MID LVL COLD POOL MOVES TO THE VCNTY
OF SRN CA SAT NIGHT AND SUN...THUNDERSTORMS ARE ALSO POSSIBLE.
SAN 0000
.SAN...NONE.
MARTIN
AREA FORECAST DISCUSSION
NWS SEATTLE WA
AFDSEW 845 PM PST WED MAR 22 2000
UPR LVL TROF WILL MOV ACRS W WA TONIGHT WITH UNSTBL AMS. IR SAT IMGRY
SHOWS A LARGE FIELD OF CU XTNDG BACK TO ABT 134W...WHICH WL CONTINUE
STREAMING INTO W WA. GOOD THING IS UNSTBL LAYER ISN'T TOO DEEP WHICH
WL HELP LIMIT SHOWERS TO SCATTERED VARIETY OUTSIDE OF PGTSND
CONVERGENCE ZONE.
VIS SAT IMGRY SHOWED GOOD LATE AFTERNOON LEE SIDE CLEARING OVER
SEATTLE AND THE NW INTR FM BEHIND THE OLYMPICS AND S VRISL
RESPECTIVELY...WITH PGTSND CONVERGENCE ZONE IN THE MIDDLE. THE PSCZ
MOVED OVR THE CASCD FOOTHILLS BRIEFLY THIS EVENING BUT HAS NOW
DEVELOPED BACK WWD OVR WRN SNOHOMISH CNTY AND ALG THE KING/SNOHOMISH
CNTLY LINE. WLY GALE GOING STRONG THRU STRAIT BUT WITH INCRS IN E
ENTRANCE WINDS...WNDS IN PGTSND HAVE BACKED OFF. GRADS ALSO LOOK LIKE
THEY HAVE PEAKED. NEW 00Z MDLS SMLR TO OLD 12Z RUN AND SHOW MAIN AMS
INSTABLITY IS TONIGHT. AMS BEGINS TO STABILIZE THU AS UPR TROF MOVS
E...BUT STILL UNSTBL ENOUGH FOR SCT SHWRS IN FCST. BASED ON SATELLITE
AND MDLS WL TRIM POPS BACK TO SCT VARIETY XCP FOR PGTSND CONVERGENCE
AREA NR KPAE. NO UIL RAOB BUT ACARS DATA SHOW PGTSND FRZLVL NR 4000
FT.
NEW AVN IS CONSISTENT WITH OLD MRF IN DIGGING MAIN ENERGY FM UPSTREAM
SYSTEM DOWN TWD CA...AND MOVING AN ELONGATED UPR TROF TO 130W FRI
AFTN. MAIN DIFF IN NEW 00Z MDLS IS AVN BRINGS AN IMPULSE ACRS WA AFT
MIDDAY FRI ALONG WITH SOME LIGHT PCPN WHILE ETA HOLDS IT OFF CST. WL
DELAY SIGNIFICANT CHGS TO MIDSHIFT. KAM
UIL 5531 SEA 4421 OLM 4421
.KATX...VCP21/CSR21...OPERATIONAL.
.SEW...GALE WARNING CENTRAL AND E ENTRANCE TO STRAIT.
SMALL CRAFT ADVISORY CST FOR HEAVY SWELL.
N