Forecast Discussions mentioning ACARS, received at FSL on 06/18/99

...SYNOPSIS... WEAK HIGH PRESSURE WILL HOLD OVER SOUTHERN CALIFORNIA THROUGH THE WEEKEND WITH SEASONALLY WARM TO HOT TEMPERATURES INLAND. NIGHT AND MORNING COASTAL LOW CLOUDS AND FOG WILL PERSIST NEAR THE BEACHES EACH AFTERNOON. FOR THE MOUNTAINS AND DESERTS...SOME MONSOONAL MOISTURE FROM ARIZONA IS EXPECTED TO DRIFT WESTWARD DURING THE WEEKEND WITH AFTERNOON CLOUDS EACH DAY AND A SLIGHT CHANCE OF THUNDERSTORMS SUNDAY AFTERNOON. ...DISCUSSION... WK HIGH PRESSURE ALF WL CONTINUE ACROSS SRN CA THRU THE WEEKEND WITH SEAONALLY WARM TEMPERATURES INLAND AND WITH CSTL NIGHT AND MORNING LOW CLOUDS AND FOG PERSISTING NEAR THE BEACHES EACH AFTERNOON. SOME MONSOONAL MSTR FM AZ WL BEGIN TO DRIFT INTO ERN SXNS OF SRN CA DURG THE WEEKEND WITH AFTERNOON CLOUDS OVR THE MTNS AND A SLIGHT CHANCE OF THUNDERSTORMS SUN AFTERNOON. EVENING ROABS/ACARS SOUNDINGS SHOW LTL CHANGE FM 24 HOURS AGO WITH THE BASE OF THE MARINE INVERSION ALG THE CST FM NR 1200 FT LAX TO 1500 FT SAN TO NR 2500 FT IN THE INLAND VLYS. SYNOPTIC AND MDL SUPPORT FOR A CSTL EDDY HAS WKND WITH STRATUS TONIGHT TO BE TRANSPORTED INLAND WITH THE WK ONSHR FLOW. MARINE LYR DEPTH IS STILL SUFFICIENT FOR PATCHY LOW CLOUDS/FOG TO REACH INLAND VLYS BY MORNING. LACK OF DECR IN THE INVERSION HEIGHT IN THE INLAND VLYS SUGGESTS HIGH TEMPERATURES IN THE INLAND EMPIRE FRI MAY BE CLOSER TO NGM MOS GUIDANCE THAN THE HIGHER TEMPERATURES IN THE CURRENT ZONE PACKAGE. THE MID SHIFT MAY WANT TO TAKE A CLOSER LOOK AT THIS. IN GENERAL...SLIGHT 850MB TEMPERATURE AND 1000-500MB THICKNESS INCREASES DURING THE NEXT 48 HOURS SHOULD SUPPORT SOME ADDITIONAL INLAND WARMING WITH IMMEDIATE CSTL SXNS REMAINING COOL DUE TO THE PERSISTENT CSTL STRATUS. AS AN ASIDE... TODAY WAS THE 56TH DAY IN A ROW THAT LINDBERGH FIELD HAS REPORTED AN AVERAGE DAILY TEMPERATURE THAT WAS NOT ABV NORMAL.

CSTL...SOME S TO SW SWELL GENERATED FM A STORM OFF THE CST OF NEW ZEALAND LATE LAST WEEK...SHOULD BEGIN ARRIVING AT THE BEACHES SAT AND CONTINUE THRU THE WEEKEND WITH MDT SURF FOR S AND SW FACING BEACHES.

EXTENDED...NCEP MARGINALLY FAVORED THE MRF OVR THE W VERSUS THE GREATER TROUGHING ALG THE W CST SHOWN BY THE EURO MDLS. THIS WOULD SUPPORT AT LEAST SOME CONTINED MINOR TRANSPORT ON MONSOONAL MSTR INTO THE ERN DESERTS AND SRN MTNS OF SRN CA THRU EARLY NEXT WEEK FOR SOME AFTERNOON CLOUDS AND A SLIGHT CHANCE OF THUNDERSTORMS. LTL CHANGE MOST AREAS OTHERWISE.

SAN 0000

.SAN...NONE.

MARTIN



18Z SFC ANLYS HAS 1027MB HIGH CNTRD OVR DBQ. 1748Z ACARS SOUNDING FROM ORD SHOWS STRONG INVERSION AND -0.3 DEG C AT 6KFT...ALLOWING FOR RATHER FLAT SCT-BKN CU. WITH SUCH COLD AIR ALOFT AND NE WINDS OFF OF LAKE MICHIGAN...AFTN TEMPS ONLY IN LOWER 60S ACROSS NRN IL/NW IND.

MODELS IN VERY CLOSE AGREEMENT IN BUILDING SFC HIGH INTO NE IL BY 12Z FRI. DRY AIR...CLR SKIES AND CALM WINDS SHOULD ALLOW FOR EXCELLENT RADIATIVE COOLING TNGT...AND WE SHOULD SET NEW RECORD LOW TEMPS FOR JUNE 18TH FOR BOTH CHI AND RFD. OLD RECORD LOW FOR BOTH CITIES IS 47. H85 TEMPS THEN WARM GRADUALLY INTO THE WEEKEND...ALLOWING READINGS TO GET BACK CLOSER TO NORMAL.

TWO S/WV TROFS APPROACHE THE AREA ON SAT...ONE DROPPING TO OUR SOUTH AND ONE FROM THE NORTH ACROSS THE WRN GRTLKS. MODELS PLACE BEST H85 THERMAL ADVECTION AND MOISTURE CONVERGENCE FM NRN IA INTO WI BY 18Z SAT...ALTHOUGH AIRMASS INITIALLY RATHER DRY. WL KEEP A LOW POP FOR SAT AFTN.

THANKS MKX FOR COORD.

.CHI...NONE

RATZER

SFC PATTERN HAS CHANGED SLGTLY DURG THE PAST 24 HRS...AS EDDY CRCLN HAS DISSIPATED...AS SUGGESTED BY YESTERDAYS MODELS. MARINE LYR DEPTH CONTS TO BE QUITE SIMILAR TO WED...WITH SOUNDINGS AND ACARS DATA SHOWING THE INVERSION BASE BETWEEN 1500 AND 2000 FT. AT THIS DEPTH...LOW CLDS AND LCLLY DENSE FOG MAY SPILL INTO SOME VLY LOCATIONS ONCE AGAIN OVERNIGHT...BUT LACK OF EDDY CRCLN MAY MAKE IT DIFFICULT FOR CLDS TO WRAP INTO WRN SAN FERNANDO VLY OR VTU COUNTY VLYS. VSBYS HAVE DROPPED ACRS CSTL SXNS OF SBA AND VTU COUNTY...A POSSIBLE INDICATION THAT THE MARINE INVERSION WAS IN THE PROCESS OF LOWERING ACRS THE NWRN HALF OF THE FCST AREA. WITH THE WAY VSBYS ARE TRENDING...A DENSE FOG ADVISORY MAY BE NEEDED FOR CSTL SXNS OF SBA AND VTU COUNTY. FOR NOW...WL UPDATE THE ZONES TO ADD SOME PATCHY DENSE FOG...AND TWEAK TEMPS A BIT. UPR RIDGE WL CONT TO STRENGTHEN SOMEWHAT ON FRI WITH THICKNESSES... H85 AND BOUNDARY LYR TEMPS CONTG TO RISE THRU SAT. THIS SHOULD CAUSE A COUPLE OF DEGS OF WARMING EACH OF THE NEXT TWO DAYS IN THE MTNS AND DSRTS...AND MOST VLY LOCATIONS AS WELL. WITH NO EDDY CRCLN...MARINE LYR DEPTH COULD BE SQUEEZED DOWN A COUPLE OF HUNDRED FT...LESSENING ITS INFLUENCE IN THE VLYS AND CAUSING A BIT MORE SUBSTANTIAL TEMP INCRS THERE. WITH UPR LVLS WARMING THE PAST COUPLE OF DAYS...INVERSION HAS STRENGTHENED SOME...AND NOT SURPRISINGLY...LOW CLDS HUNG TOUGH ALG THE IMDT CST TODAY. THIS WILL LIKELY HAPPEN AGAIN ON FRI...AND POSSIBLY SAT AS WELL.

OVERALL UPR PATTERN SHOULD REMAIN QUITE SIMILAR THROUGH SAT... WITH UPR LVL FLOW BECOMING INCRGLY MOIST DURG THE WEEKEND AND SOMEWHAT FAVORABLE FOR THE DVLPMENT OF SOME SHWRS/TSTMS ACRS THE MTNS AND DSRTS BY SUNDAY AND CONTG AT LEAST INTO MON.

LAX 0000. BRUNO.

.LAX...SMALL CRAFT ADVISORY...SEE LAXCWFLAX.

LATEST SFC ANAL HAS HI OVR SRN LK MICH. SOUNDINGS INDICATE FAIRLY ADIABATIC THRU 850 MB FOR ALL BUT CHI ACRDG TO ACARS. ALL HAVE A WEAK INVERSION ABV 850. W/O GOING SUPER WUD EXPECT TEMPS TO CAP AROUND 70. THE LEAN IS TWRD ETA MODEL WHICH HAS PERFORMED WELL LAST FEW RUNS. ETA A TAD QUICKER THAN OTHERS AND NGM OVRBLOWN ON RH. BUT ALL MODELS INDICATE RDG TO CONT SLIDING EWD AND SE WINDS OVR RGN BY MIDDAY. SE TRAJ TO CENTRAL INDIANA DIDNT MAKE IT TO MID 70S EITHER EVEN WITH FULL SUN ACRDG TO SATL. SO WUD WANT TO HOLD BACK TO EITHER ARND 70 TO 70-75 RANGE WITH MID 60S AT LAKE. WHILE WAA BEGINS TO RETURN TNGT AND SAT...ALL MODELS TEND TO HOLD PCPN BACK TO SAT NGT...MAYBE EVEN SUN IF SLOW DOWN THE ETA. PVA SHOT MOVG INTO PLAINS WEAKENS AS IT APPROACHES MS RVR SAT. THEREFORE WILL GO DRY FOR SAT...JUST PTCLDY. WLL TEND TO BRING IN SOME CI TO NRN IL TNGT BUT THINK FAIR FOR NERN IL A BETTER CHOICE THAN PTCLDY. NO RECORD TEMPS TO WORRY ABT TNGT EITHER.

.CHI...NONE

BRUMER

UPDATE MAY BE NEEDED TO TWEAK SOME HIGH TEMPS TODAY...CONCERNED ABOUT ONSHORE FLOW LIMITING THE WARMING IN FORECAST.

FOR THE NEXT 12 HOURS...PROFILER AND ACARS DATA BOTH SHOWING A SHALLOWER MARINE LAYER IN PLACE THIS AM. ACARS DATA SHOWING THE TOP OF THE MARINE LAYER AT 1500 FEET OVR LAX. USC PROFILER INDICATING THE TOP SOMEWHERE AROUND 1200 FEET. THIS IS IN CONTRAST TO YESTERDAY WHEN THE MARINE LAYER WAS AROUND 2000 FEET DEEP. SO INDEED...THE MARINE LAYER IS DROPPING AS EXPECTED. THE MAIN FORECAST QUESTION...HOW WARM CAN THE COASTAL AND VALLEY SECTIONS GET WITH A FAIRLY SHALLOW MARINE LAYER YET CONTINUED ONSHORE FLOW. CURRENT HIGH TEMPS LOOK A TAD HIGH...YET WITHIN THE BALLPARK SO PROBABLY WILL LEAVE ALONE.

FOR THE 12 TO 48 HOUR PERIOD...BY TONIGHT THE MESO-ETA SHOWS A MAJOR DROP IN LOW LEVEL RH WHICH WOULD INDICATE LITTLE IN THE WAY OF COASTAL LOW CLOUDS. HOWEVER...THE MESO-ETA ALSO SHOWS A CONTINUATION OF ONSHORE FLOW IN THE MSL PRESSURE FIELD...WHICH WOULD KEEP LOW CLOUDS ALONG THE COAST. THIS INTERNAL INCONSISTENCY RENDERS THE MESO-ETA A LITTLE LESS RELIABLE THAN NORMAL. THE ETA AND AVN BOTH SHOW CONTINUED ONSHORE FLOW THROUGH SAT. ALL MODELS SHOWING AN INCREASE IN HEIGHTS AND 850 MB TEMPS OVER THE CWA. THEREFORE...BELIEVE THAT THE WARMING TREND WILL OCCUR...BUT A LITTLE SLOWER THAN CURRENTLY FORECAST. WILL PROBABLY SCALE BACK SAT HIGH TEMPS A COUPLE OF DEGREES THIS AFTERNOON.

EXTENDED...AGREE WITH PREVIOUS SHIFT THAT THE SOUTHEAST FLOW ALOFT FOR THE LATE WEEKEND LOOKS TOO DRY TO GET TOO EXCITED ABOUT. MOISTURE WILL HAVE A LONG WAY TO TRAVEL FROM EASTERN ARIZONA. MAY INCLUDE SOME AFTN BUILDUPS BY SUN AFTN.

LAX 000. SWEET.

.LAX...NONE.