Forecast Discussions mentioning ACARS, received at FSL on 09/15/99

MORNING VISIBLE SATELLITE PICTURES SHOW VERY SHALLOW MARINE LAYER ALONG THE COAST EXTENDING INLAND ALONG THE COLUMBIA RIVER AND THROUGH THE CHEHALIS GAP. LOW ST AS FAR NORTH AS KTIW AT 15Z. PIREP JUST SOUTH OF KOLM INDICATING TOPS 700 FEET. WITH SUCH A SHALLOW MARINE LAYER INLAND EXPECT ST TO BURN OFF BEFORE MORNING ZONE PACKAGE FOR INTERIOR LOCATIONS BUT WITH TEMPS WARMING UP FAST OVER THE INTERIOR ST ALONG THE COAST WILL BE TOUGH TO BURN OFF. MORNING ACARS SOUNDINGS OVER KSEA SHOW TOP OF THE INVERSION AROUND 3000 FEET AND MAX TEMPERATURES WITH INVERSION BREAKING IN THE MID 80S. LOCAL MAX TEMP STUDY FOR KSEA SHOWS 1 DEGREE OF COOLING TODAY VERSUS YESTERDAYS MAX BUT ACARS SOUNDINGS SHOWING VERY LIGHT WINDS ALL THE WAY UP THROUGH 5000 FEET WHICH WILL HELP THINGS WARM UP. ALL THIS LEADS TO MAX TEMPS INLAND SIMILAR TO YESTERDAY. MORE MARINE AIR GETTING INLAND ON WED WITH STRONG THERMAL GRADIENT BETWEEN COAST AND INTERIOR SECTIONS THIS AFTERNOON. WILL KEEP AN EYE ON KHQM-KSEA GRADIENT. FIRST LOOK AT NEW MODEL RUNS SHOWING WEAK PUSH WEDNESDAY MORNING FOR 5 TO 10 DEGREES OF COOLING IN THE INTERIOR WHICH IS RIGHT IN LINE WITH CURRENT FORECAST. FELTON UIL OLM SEA 000

.KATX...VCP32/CSR32...OPERATIONAL.

.SEW...SCA STRAIT OF JUAN DE FUCA.

...SYNOPSIS... A WEAK UPPER TROUGH WILL REMAIN ALONG THE WEST COAST THROUGH THE WEEKEND WITH WEAK ONSHORE FLOW FOR SOUTHERN CALIFORNIA. FAIR WEATHER WILL CONTINUE THROUGH THE WEEKEND WITH SEASONAL TEMPERATURES INLAND AND BELOW NORMAL TEMPERATURES AT THE COAST. A COASTAL EDDY WILL BRING EXTENSIVE LOW CLOUDS AND FOG WEST OF THE MOUNTAINS THIS MORNING. FOR TONIGHT THROUGH THE WEEKEND...NIGHT AND MORNING COASTAL LOW CLOUDS AND FOG WILL EXTEND LOCALLY INTO THE INLAND VALLEYS.

...DISCUSSION... A WEAK UPPER TROUGH WILL CONTINUE ALG THE W CST THRU FRI WITH WK ONSHR FLOW FOR SRN CA. A CSTL EDDY WL CONTINUE THRU THIS MORNING AS SHOWN BY THE 12Z AND 00Z COAMPS..THEN DISSIPATE THIS AFTERNOON. ONSHR FLOW FOR THIS AFTERNOON AND THU AFTERNOON WL BE WK AND LESS THAN TUE AFTERNOON. TUE EVENING ACARS SOUNDINGS AND RAOBS SHOWED A MARINE INVERSION AROUND 1500 FT LAX TO 2000 FT ONT AND SAN/NKX. EXPECT A MARINE LYR DEPTH OF AROUND 2000 FT THIS MORNING FOR MOST AREAS WITH LTL CHANGE OR A SLIGHT DECR FOR TONIGHT AND THU MORNING. THIS DEPTH IS SUFFICIENT FOR LOW CLOUDS TO SPREAD INTO THE INLAND EMPIRE BY MORNING WITH THE PUSH PROVIDED BY THE EDDY. ADJUSTMENT BY THE SWING SHIFT HAS THIS COVERED. HOWEVER...WITH WK OFHSR PRESSURE TRENDS DEVELOPING TONIGHT AND THE GENERAL WKNESS OF THE ONSHR FLOW FOR THIS AFTERNOON AND EVENING...BELIEVE STRATUS WL HAVE A MORE DIFFICULT TIME REACHING THE INLAND EMPIRE TONIGHT AND THU MORNING AND HAVE THUS TRIMMED BACK LOW CLOUD WORDING FM "AREAS" TO "PATCHY" FOR THOSE TIME PDS. LATEST (00Z) COAMPS SHOWS THE EDDY DISSIPATING WITH WK ONSHR FLOW THIS AFTERNOON...HENCE CLEARING FOR MOST LOCATIONS BY AFTERNOON INCLUDING THE BEACHES. HOWEVER...COAMPS ALSO SHOWS THE EDDY REDEVELOPING THIS EVENING...THUS LOW CLOUDS SPREADING INLAND BY LATE AFTERNOON OR EARLY EVENING. COAMPS 10 METER AGL TEMPERATURE FORECASTS ON THE INTERMEDIATE 18 KM GRID HAVE DONE A REASONABLY GOOD JOB IN SHOWING THE AREAS OF MOST EXTENSIVE STRATUS...SHOWING MUCH OF THE STRATUS REMAINING OFF THE S CST THE PAST FEW DAYS...THEN SHOWING THE GREATER INLAND PENETRATION INTO THE INLAND VLYS THIS MORNING. LATEST COAMPS IMPLIES LESS INLAND PENETRATION OF STRATUS TONIGHT/THU MORNING...CONSISTENT WITH THE LESSER PENETRATION EXPECTED WITH WK OFSHR TRENDS AT NIGHT AND REFLECTED IN THE CURRENT FORECAST PACKAGE.

EXTENDED...ONLY MINOR DAY TO DAY CHANGES AS A WK UPR TROUGH REMAINS OVR CA WITH WK ONSHR FLOW FOR SRN CA. THRU THE WEEKEND...SEASONAL TEMPERATURES INLAND...BLO NORMAL TEMPERATURES AT THE CST...DRY ALL AREAS AS MONSOONAL MSTR REMAINS TO THE E...AND AREAS OF NIGHT AND MORNING CSTL LOW CLOUDS EXTENDING LCLLY INTO THE INLAND VLYS.

SAN 000

.SAN...NONE.

MARTIN

EDDY CIRCULATION HAS SPUN UP AND THIS WILL RESULT IN LATER CLEARING AND COOLER TEMPS JUST ABOUT EVERYWHERE EXCEPT THE MTNS AND DSRTS. LA BASIN PROFILER AND ACARS REPORTS INDICATE MARINE LYR HAS DEEPENED TO AROUND 2500 FEET THIS MORNING...WHILE VBG SOUNDING INDICATES MARINE INVERSION HAS STRENGTHENED CONSIDERABLY SINCE YESTERDAY. THIS COMBINATION TYPICALLY RESULTS IN A VERY STUBBORN BURN OFF AND SOME BEACHES MAY REMAIN CLOUDY AND COOL ALL DAY. THE ONLY FACTOR WORKING IN OUR FAVOR IS A WEAK ONSHORE FLOW...BUT THIS WILL RESULT IN VERY HAZY CONDITIONS ACROSS THE BASIN IN PLACES WHERE THE SUN DOES COME OUT.

SEE VERY LITTLE CHANGE IN THIS PATTERN NEXT 48 HOURS. CYCLONIC FLOW ALOFT WILL REMAIN IN PLACE AS THE PERSISTANT SUMMER TROF LINGERS AND IN FACT DEEPENS SOMEWHAT THRU THE PERIOD. WE SHOULD SEE A WEAKENING OF THE OUTER WATER WINDS LATER TONIGHT AND FRI WHICH WILL REDUCE THE SUPPORT FOR THE CSTL EDDY. HOWEVER...OVERALL DON'T SEE MUCH CHANGE RIGHT ON THRU THE WEEKEND AND INTO EARLY NEXT WEEK.

ISSUED A BRIEF UPDATE EARLIER TO BRING TEMPS DOWN A COUPLE DEGREES...MAINLY IN THE VALLEYS.

LAX 000. WOFFORD

.LAX...SMALL CRAFT ADVISORY (SEE LAXCWFLAX).

GOOD MARINE PUSH OVERNIGHT...SINCE WE'RE BURIED IN STRATUS/FOG THIS MORNING. USING ACARS DATA FOR LOW LVL TEMPS NEAR THE 1700-2000 FT ST TOPS...A BREAKOUT TEMP SHOULD BE SOMEWHERE NEAR 64F TODAY...OR SOMETIME AROUND NOON. UNNECESSARY TO MODIFY BREAKOUT TIME FOR CONTINUING STRONG ONSHR FLOW SINCE ALL GRADS 1 MB OR LESS THIS MORNING. THU MORNING LOOKS LIKE A REPEAT XCP FOR STGR ONSHR FLOW THIS EVENING AND SLGTLY STGR ONSHR GRADS THU MORNING. XPCT LESS LIFR CONDS AND HIR TOPS...BUT SLGHTLY LATER BREAKOUT. OTHERWISE...WK UPR TROF MOVS ACRS CNTRL B.C. LATE THIS AFTN...AS IT SHEARS AWAY WKNG GLFAK LOW. WK SFC FNT W OF OFSHR WATERS DISSOLVES AS SFC RDGG TAKES OVER BHND FNT. IN FACT...THIS RDGG IS WHAT HELPS INCRSS OUR ONSHR GRADS THIS EVENING.

IN FRI-SUN TIMEFRAME...MRF HAS BEEN CONSISTENT FOR THE PAST 3 RUNS IN PLACING THE NEXT UPR RIDGE OVR B.C. AND PACNW SAT AFTN. IT HAS ALSO TRENDED STRONGER WITH EACH RUN AS WELL AS SLOWER WITH THE TRAILING UPR LVL TROF. ECMWF/UKMET/CANSP VRY SMLR. CURRENT FCST LOOKS GOOD XCP NR 90 SW INTR SEEMS A TAD HIGH FOR SAT GIVEN JUST 24HR OF ELY FLOW. ANOTHER 2 DAY PUSH LOOKS GOOD STARTING SUN AFTN GIVEN STEADY PROGRESSION OF UPR RDG AND NXT WK APCHG TROF. KAM UIL 111 SEA 000 OLM 000

.KATX...VCP32/CSR32...OPERATIONAL. RADAR WILL BE DOWN LATER THIS MORNING FOR MAINTENENCE.

.SEW...SCA CENTRAL STRAIT OF JUAN DE FUCA.