Forecast Discussions mentioning ACARS, received at FSL on 04/13/01

...SYNOPSIS... FAIR WEATHER WILL BE EXPECTED THE NEXT FEW DAYS. THE ONSHORE FLOW WILL BE WEAK TONIGHT...BUT IT WILL STRENGTHEN AND ALLOW FOR A NEW MARINE LAYER TO DEVELOP BY FRIDAY NIGHT WITH THE RESULTING INCREASE IN THE COASTAL LOW CLOUDS. TEMPERATURES WILL INCREASE OVER MOST AREAS FRIDAY...THEN LITTLE CHANGE IS EXPECTED OVER THE WEEKEND.

...DISCUSSION... SKIES HAVE MOSTLY CLEARED OUT THIS EVENING. ACARS SOUNDINGS INDICATE THAT THE OLD INVERSION AROUND 4000 FEET IS ERODING AWAY AND HAS TURNED INTO A SEMI-ISOTHERMAL LAYER FROM 4000-7000 FEET...WHILE A NEW INVERSION APPEARS TO BE FORMING SOMEWHERE IN THE 1000-1500 FOOT RANGE. THIS IS QUITE PLAUSIBLE GIVEN THE SUBSIDENCE WE HAVE NOW. WE ALSO HAVE OFFSHORE TRENDS AT THE SURFACE...AND THE 850 MB FLOW IS SLIGHTLY OFFSHORE. SO...IF ANY LOW CLOUDS FORM TONIGHT...THEY SHOULD BE RESTRICTED TO NEAR THE COAST. WITH DEW POINTS IN THE 40S TO AROUND 50...I DOUBT IF TOO MUCH FOG SHOULD FORM...THOUGH I WILL REWORD THE FORECAST FOR COASTAL ZONES AS PATCHY LOW CLOUDS AND FOG FOR LATE TONIGHT.

TEMPS SHOULD INCREASE GENERALLY 5-10 DEG FRIDAY IN MOST AREAS DUE TO THE CORRESPONDING INCREASE IN 850 TEMPS...EXCEPT THE IMMEDIATE COAST WHICH WILL STRUGGLE TO GET MUCH ABOVE 60 DUE TO THE 60-ISH DEGREE OCEAN TEMPS. DUE TO A SLIGHT INCREASE IN THE TROUGHING OFF THE COAST LATE FRIDAY...WE SHOULD ONCE AGAIN RETURN TO DEFINITE ONSHORE FLOW AT THE SURFACE AND AT 850 MB...SO A MARINE LAYER SHOULD BECOME WELL-ESTABLISHED FRIDAY NIGHT/SATURDAY...AND MAY DEEPEN ENOUGH TO COOL SOME COASTAL VALLEYS...ESPECIALLY SAN DIEGO COUNTY...DESPITE WHAT MOS SAYS WITH ITS 1 OR 2 DEGREE INCREASE. MOST OTHER AREAS SHOULD SEE LITTLE TEMPERATURE CHANGE ON SAT.

IT APPEARS THE RIDGE THAT DEVELOPS EARLY NEXT WEEK WILL MOSTLY DEVELOP TO OUR EAST...SO EXPECT WARM WEATHER OVER THE MTNS/DESERTS BUT SOME LOW CLOUDS CLOSER TO THE COAST. IN THE UPDATE...I WILL TONE DOWN THE OPTIMISM IN THE EXTENDED A BIT...AT LEAST NEAR THE COAST. ANOTHER TROUGH MIGHT MOVE IN LATE IN THE WEEK.

THE ZONE UPDATE WILL BE OUT SOON.

SAN 0000

.SAN...NONE.

MAXWELL



...SYNOPSIS... THE MARINE LAYER AND WEAK ONSHORE FLOW WILL PERSIST THROUGH SATURDAY...WITH MORNING CLOUDS GIVING WAY TO MOSTLY SUNNY SKIES EACH AFTERNOON. ON SUNDAY...HIGH PRESSURE WILL BUILD OVER THE SOUTHWEST AND BRING WARM DRY WEATHER THROUGH THE MIDDLE OF NEXT WEEK.

...DISCUSSION... ACARS SOUNDINGS SHOWED THE MARINE LAYER DEPTH NEAR 4100 FEET THIS AFTERNOON...A DRAMATIC DECREASE FROM THE 6800 FOOT DEEP LAYER THE MORNING. REVERSE CLEARING DEVELOPED THIS AFTERNOON WITH SUNNY SKIES AT THE COAST AND STRATOCUMULUS INLAND. SCATTERED TO BROKEN CLOUDS IN AND WEST OF THE MOUNTAINS WILL LIKELY LINGER OVERNIGHT.

MEAN ZONAL FLOW AND WEAK ONSHORE GRADIENTS WILL KEEP THE MARINE LAYER INTACT THROUGH SUNDAY WITH MORNING CLOUDS EACH DAY. THE MOST EXTENSIVE CLOUD COVER WILL LIKELY BE SATURDAY MORNING AS A WEAK SHORTWAVE PASSES OVER SOCAL FRIDAY NIGHT. AS A RESULT...TEMPERATURES IN THE COASTAL AREAS WILL BE ONLY A COUPLE DEGREES WARMER OVER THE WEEKEND...BUT 10 TO 15 DEGREES WARMER ABOVE THE MARINE LAYER IN SOME OF THE FOOTHILLS AND MOUNTAINS. DESERTS WILL ALSO WARM NICELY AS 850 MB TEMPS JUMP FROM +8C TODAY...TO +12C FRIDAY...TO +14C SATURDAY.

IN THE EXTENDED...A BUILDING UPPER RIDGE IN RESPONSE TO DEEPENING EAST PAC LOW WILL BRING WARM DRY WEATHER THROUGH THE MIDDLE OF NEXT WEEK WITH ABOVE AVERAGE TEMPERATURES. SUCCESSIVE RUNS OF THE MRF HAVE PUSHED BACK THE ONSET OF HEIGHT FALLS AND SIGNIFICANT COOLING WHICH NOW LOOKS LIKE IT WILL ARRIVE LATER IN THE WEEK.

SAN 000

.SAN...NONE.

MOEDE



SYNOPSIS...WITH THE STRONG CYCLONE NOW MOVING WELL AWAY TO NE SURFACE ANTICYCLONE OVER WRN IOWA THIS MORNING WILL SLIDE ACROSS NRN ILLINOIS TODAY. ANOTHER WEAK DISTURBANCE OVER THE WESTERN HIGH PLAINS IS EXPECTED TO SKIP THROUGH THE WESTERN LAKES TONIGHT AND EARLY SUNDAY. MUCH COOLER AIR IS ON TAP NEXT WEEK...BEGINNING LATER EASTER SUNDAY...AS AN UPPER TROUGH BUCKLES SOUTHWARD OVER THE GT LAKES.

DISCUSSION...LINGERING STRATO CU ARE THINNING OUT OVER NE ILLINOIS DURING PREDAWN HRS. ACARS FROM RFD AND ORD SHOW VERY STEEP LAPSE RATES TO AROUND 850MB WHERE SOLID THERMAL LID EXISTS. WITH LAPSE RATES ABOUT ADIABATIC ALREADY ANY WARMING WILL BE A STRUGGLE THIS MORNING BUT AS SLIGHT WARM ADVECTION SETS IN THIS AFTERNOON AND STRONG SUN WORKS ON QUIET AIRMASS TEMPS LIKLEY WILL PEAK ARND 60 OR SO. EXPECT ONSHORE LAKE BREEZE TO DEVELOP EARLY AFTERNOON KEEPING LAKESHORE AREAS IN LOW 50S.

AS SURFACE HI DRIFTS BY LATER TODAY WEAK SW FLOW WILL PRECEED ANOTHER WEAK FRONTAL BOUNDARY EXPECTED AROUND SUNRISE SAT. BAND OF MID CLOUDS LIKELY TO AFFECT NRN IL TONIGHT HOLDING TEMPS UP A BIT. ONLY MINIMAL THREAT OF SPRINKLES TOWARD WISC BORDER AND WILL OMIT FROM GOING FCST.

A REPEAT OF TODAY IS A GOOD BET FOR SAT WITH MORNING CLOUDS GIVING WAY TO SUNSHINE. MEAN 850 TEMPS A BIT HIGHER ON SAT THAN TODAY IMPLYING A LITTLE WARMER TEMPS.

DEEPENING OF ERN CANADIAN TROUGH INTO GT LAKES BEGINS ON SUNDAY WITH INITIAL FRONTAL PASSAGE EXPECTED THEN. MODELS EXPECT A SURFACE LOW TO DEVELOP IN SRN BRANCH OF WESTERLIES SAT NIGHT OVER SRN PLAINS AND MOVE UP OHIO VALLEY SUNDAY. IF THIS OCCURS MOISTURE FEED INTO DIGGING CD FRONT WILL BE SHUT OFF AND ONLY MINMAL THREAT OF FRONTAL PRECIP IS EXPECTED. HAVE SOME DOUBTS ABOUT LACK OF CLOUDS IN SUNDAY FCST BUT WILL LEAVE OPTOMISTIC FOR NOW. OTHERWISE EXTENDED CRASH IN TEMPS WITH THREAT OF SNW SHOWERS ABOUT TUE SEEMS REASONABLE FROM 5 DAYS AWAY.

CLOSER IN TIME..MOS/FAN TEMPS GENERALLY REASONABLE ALTHOUGH MAXS ON SAT WILL BE TEMPERED TOWARD COOLER FAN/MRF NUMBERS. KML

...CHI...NIL



SKIES MOSTLY CLEAR ACROSS FORECAST AREA THIS MORNING...DUE TO OFFSHORE TRENDS. 12Z SOUNDINGS AND ACARS DATA SHOWING SUBSTANTIAL WARMING IN THE BOUNDARY LAYER THIS MORNING...AS COMPARED TO 24 HOURS AGO. THIS COMBINED WITH MORE SUNSHINE TODAY SHOULD ALLOW FOR WARMING TREND IN ALL AREAS. BASED ON SOUNDING DATA...APPEARS THAT MOST SUBSTANTIAL WARMING TODAY WILL OCCUR IN THE MOUNTAINS... WHERE THERE IS A 7 TO 10 DEGREE RISE BETWEEN THE 900 AND 800 MB LEVEL. EARLIER MORNING UPDATE HAS ACCOUNTED FOR THE RISE IN TEMPERATURES TODAY.

OVER THE NEXT 48 HOURS...FLAT ZONAL PATTERN WILL CONTINUE AT UPPER LEVELS. NEAR THE SURFACE...THERE WILL BE WEAK OFFSHORE GRADIENTS IN THE MORNING...THEN MODERATE ONSHORE FLOW DURING THE AFTERNOON AND EVENING HOURS. THIS WILL KEEP TEMPERATURES NEAR SEASONAL LEVELS THROUGH THE WEEKEND. ONLY OTHER CONCERN WILL BE INCREASING NORTHWEST FLOW ACROSS THE OUTER COASTAL WATERS LATER TODAY AND TONIGHT...WHERE A GALE WARNING WILL BE ISSUED. THIS INCREASING NORTHWEST FLOW WILL LIKELY SPIN UP AN EDDY CIRCULATION...WHICH COULD BRING A RETURN OF STRATUS FROM LA COUNTY SOUTHWARD BY SATURDAY MORNING.

LAX 000. GOMBERG.

.LAX...GALE WARNING/SMALL CRAFT ADVISORY (SEE LAXCWFLAX).



SATELLITE IMAGERY SHOWING A BAROCLINIC LEAF DEVELOPING OVER THE REGION. RAIN OVER EASTERN MD AND DE NOT FCST BY ANY OF THE MODELS I/VE SEEN INCLUDING MM5.

BASED ON EXTRAPOLATION...MAIN RAINFALL EXPECTED TO STAY SOUTH AND EAST OF EASTERN LI. A FEW SPRINKLES FORM THE MID CLOUDS UNTIL NOON ARE POSSIBLE.

BACK EDGE OF THE BAROCLINIC CLOUDS ARE TRANSLATING EAST AT 50 KTS. THIS PLACES THE CLEARING INTO WESTERN ORANGE AROUND 1530Z AND OVER EASTERN LI AROUND 1800Z.

WILL ISSUE AN UPDATE TO CLEAN UP WORDING OF 1ST PERIOD OF ZONE.

WINDS...SOUNDING AND ACARS DATA SHOWING A STRONG LOW LEVEL INVERSION. WITH FCST SOUNDINGS HAVING A DRY ADIABATIC LAPSE RATE IN THE LOWEST LEVELS THIS AFTERNOON...THIS ALLOWS THE WEST/NORTHWEST WINDS TO WORK DOWN (GUST) IN THE 20 TO 25 KT RANGE.

MAX TEMPS FROM THE 12Z OKX SOUNDING WERE NEAR 80...BUT ACARS FROM EWR IS CLOSER TO 70. COLD ADVECTION THIS AFTERNOON WILL KEEP TEMPERATURE FROM REACHING THESE POTENTIAL LEVELS. WILL GO WITH THE CURRENT FCST HIGH DESPITE PRESENT TEMPS THAT ARE ABOVE THE LAMPS GUIDANCE TRENDS.

NO MAJOR SYSTEMS IN TERMS OF PCPN FOR THE WEEKEND AND WILL LOOK AT THE EXTENDED FOR NEXT WEEKS DEEP EAST COAST TROF IN THIS AFTERNOON/S DISCUSSION. THIS TROF APPEARED YESTERDAY TO BE VERY CONSISTENT IN THE NCEP ENSEMBLES AND WAS 2 SIGMA BELOW MEAN.

MARINE...WINDS WILL HAVE A HARD TIME WORKING DOWN DUE TO THE COLD WATER TEMPS. EXPECT 15 KTS WILL BE IT MORE THAN A FEW MILES FROM SHORE. BUT...WILL KEEP SCA UP AS GUST POTENTIAL IS THERE FOR 25 KTS NEAR SHORE AND LI SOUND WILL BE NEAR 25 KT.

NOTE...DROPPED FLW FOR CTZ005-006 PER ALY'S REQUEST.

.OKX... CT...FLW FOR CT RVR CTZ007-011 (VIA WFO BOX). NJ...DENSE FOG ADV UNTIL 12Z THIS MRNG FOR NJZ002>006-011. NY...DENSE FOG ADV UNTIL 12Z THIS MRNG FOR NYZ069>081. MARINE...SCA FOR ALL WTRS...ANZ350-353-355-330-335-338.

$$

TONGUE