Forecast Discussions mentioning "ACARS", "MDCRS", or "AIRCRAFT" received at FSL on 02/19/03

AVIATION DISCUSSION REGARDING 18Z TAFS:

MAIN PROBLEM CONTINUES TO BE TIMING ON CLEARING OF LOW CLOUD DECK. SATLT LOOPS SHOW CLRG LINE NOW EXTENDS FROM MSN-RFD-JUST E OF PIA. ACARS SOUNDINGS SHOW LOW LVL INVERSION GETTING MORE SHALLOW WITH TIME SO CLRG TREND SHOULD CONTINUE ACROSS TERMINALS FROM W-E...REACHING CHI AREA BY 21Z AND GYY BY 22Z.

RMNDR OF TAF PD WILL BE VFR WITH SCT V BKN CLDS AOA 120 AND NO RESTRICTION ON VIS. COLD FRONT FCST TO TO MOVE ACRS NRN IL/NWRN IN TNGT. ASSD WIND SHIFT EXECTED TO BE GRDL...REACHING RFD ARND 06Z...CHI ABT 07Z AND SHUD CLR TERMINAL AREA BY 08Z. WINDS TO SHIFT FROM SW ARND 230 DEG TO WNW ABT 290 DEG DURG THIS TIME WITH SPEEDS IN 10 - 15 KT RANGE.

MERZLOCK

PUBLIC DISCUSSION FOR 4AM ZONES/GRIDS

LOW CLOUDS HANGING ON THIS AM BUT SHOULD BEGIN TO DISSIPATE MID TO LATE MORNING AS LOW LEVEL RH DECREASES. SOME LIGHT FOG ALSO AROUND AND MAY SEE SOME LOCATIONS DROP BELOW A MILE ESPECIALLY IF CLOUDS CLEAR WESTERN SECTIONS. WILL WATCH LATEST TRENDS BEFORE ISSUANCE TO INCLUDE FOG AND WHICH AREAS.

WEAK SYSTEM PASSES WELL TO OUR NORTH ACROSS UPPER LAKES TODAY. NEXT SYSTEM MOVES ACROSS SOUTHERN PLAINS/MISSISSIPPI VALLEY TONIGHT INTO WED. ONLY GFS BRINGS PRECIP NORTH TO SOUTHERN CWA. ALL OTHER MODELS MUCH FARTHER SOUTH AND WITH HIGH PRESSURE BUILDING ACROSS THE MIDWEST BY WED MORNING ONLY INCREASE IN CLOUD COVER EXPECTED. GUIDANCE CLOSE ON TEMPS AND PERSISTENCE PROBABLY A GOOD FORECAST NEXT FEW DAYS.

MODELS SHOWING DIFFERENT SOLUTIONS FOR FRI-SAT TIME FRAME. SFC LOW DEVELOPS OVER TX THURS NIGHT AS A VORT KICKS OUT TO THE OH VALLEY BY FRI AM. THIS TO BRING A CHANCE OF PRECIP BUT SHOULD BE LIGHT AND MAYBE FARTHER SOUTH AND EAST AS LOW DOESN/T EJECT OUT UNTIL FRI NIGHT. GFS/UKMET/CANADIAN ALL IN AGREEMENT OF A TRACK ACROSS TN/KY INTO SAT MORNING. CRITICAL THICKNESS/850MB TEMPS ALL SUPPORT MAINLY RAIN FOR WHATEVER PRECIP DOES FALL THRU FRI EVENING BEFORE COLD AIR ARRIVES FRI NIGHT. WITH THIS IN MIND WILL BACK POPS OFF TO CHANCE ALL PERIODS. AFTER THIS WITH COLD AIR IN PLACE, CLIPPER SWINGS THRU MIDWEST LATE SUN INTO MON BUT WILL LEAVE THIS FOR LATER RUNS TO PIN DOWN.

.CHI...NONE.

CMS



.SYNOPSIS...A WEATHER SYSTEM APPROACHING FROM THE NORTH WILL BRING A CHANCE OF SHOWERS OR EVENING THUNDERSTORMS WEDNESDAY NIGHT INTO EARLY THURSDAY. GUSTY WINDS WILL OCCUR BEHIND THE SYSTEM...MAINLY THROUGH PASSES AND CANYONS. HIGH PRESSURE WILL BRING FAIR AND WARMER WEATHER TOWARD THE END OF THE WEEK...THOUGH ANOTHER SYSTEM WILL CAUSE MORE CLOUDS AND COOLING EARLY NEXT WEEK.

.DISCUSSION...SKIES WERE CLEAR THIS EVENING AS HIGH CLOUDS HAVE DRIFTED SOUTHEAST OUT OF THE AREA. THE FOG LOOP INDICATES PATCHY LOW CLOUDS/FOG FORMING ALONG THE BAJA COAST...AND SHORTLY THAT SHOULD SPREAD FURTHER NORTH. ACARS SOUNDINGS SHOW NO WELL-DEFINED INVERSION...AND IF A STRONGER INVERSION FORMS OVERNIGHT...IT WILL LIKELY BE BELOW 1500 FEET. SO...LOW CLOUDS/FOG SHOULD STAY PATCHY. GROUND FOG COULD FORM IN A FEW SPOTS DUE TO THE HIGH DEW POINTS/MOIST SOIL.

THE SYSTEM FOR WEDNESDAY NIGHT IS CURRENTLY A VORT MAX NEAR 40N/130W...EASILY VISIBLE ON THE WATER VAPOR LOOP. THE TRACK SHOULD BE VERY CLOSE TO SAN DIEGO AS IT MOVES SE...THOUGH THE VORT MAX WILL BE ON THE BACK SIDE OF THE LOW AT THE TIME...SO MOST DYNAMICS SHOULD STAY OVER THE WATER. GIVEN THAT THE WATER WILL BE WARMER THAN LAND AT NIGHT...THIS WILL MAKE ANY SHOWER/TSTORM ACTIVITY MOST LIKELY OVER WATER. HOWEVER...WITH DAYTIME HEATING THU...IF THE STORM TAKES A SLOWER TRACK THAN EXPECTED...SHOWERS/TSTORMS COULD FORM OVER LAND...BUT MOST LIKELY THIS WILL OCCUR ONLY OVER BAJA. STILL...WITH 500 MB TEMPS BELOW -20 DEG C FOR MOST OF THE DAY THU AND SOME MOISTURE WRAPPING AROUND THE N SIDE OF THE LOW...A TSTORM IS NOT OUT OF THE QUESTION OVER LAND THU. AN UNDERSUPPLY OF LOW-LEVEL MOISTURE WILL KEEP POPS FAIRLY LOW BOTH WED NIGHT/THU THOUGH. OFFSHORE FLOW RAPIDLY DEVELOPS THU...BUT SINCE THE LOW GOING BY TO THE S/SW WILL BE THE COLD CORE...NO COLD AIR ADVECTION WILL BE ABLE TO AID THE WIND...SO THE CANYON/PASS WINDS FROM THE NE WILL BE GRADIENT DRIVEN. HOWEVER...GRADIENT-DRIVEN WINDS CAN BE QUITE VIGOROUS AND WIDESPREAD...SO A WIND ADVISORY MIGHT BE NEEDED.

IN THE EXTENDED...ANOTHER SYSTEM WITH A SIMILAR PATH WILL GO BY MON/TUE...AND POSSIBLY YET ANOTHER SYSTEM COULD MOVE THROUGH IN A SIMILAR WAY LATE NEXT WEEK. IF THE NEXT MODEL RUNS SHOW THE MON/TUE SYSTEM IN OUR AREA...THEN CHANCE POPS SHOULD BE ADDED TO THE EXTENDED. .SAN...NONE.

MAXWELL