209 
FXUS63 KLSX 272046
AFDSTL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
330 PM CDT SAT APR 27 2002

AFTER WAITING AND WATCHING THINGS ARE FINALLY BGNG TO GET GOING OUT 
WEST.  THE MID LVL DRY SLOT CONTS TO SURGE EWD ACRS THE FA ON THE 
HEALS OF THE ERN MO IMPULSE HELPING ALG WITH WAA GENERATE THE SECOND 
WV OF SHRA AND EMBDD -TSRA NOW MOVG EAST OF THE MS RVR.  SCT CNVCTN 
IS NOW DVLPG ALG DRYLN FM SE NEB INTO ERN KS WHERE CLDS HV CLRD AND 
DIURNAL HTG AND PBL MSTR ADVCTN HAS RESULTED IN A SWATH OF SFC BASED 
INSTABILITY.  THE BIG QUESTION IS HOW FAR EWD THE INSTABILITY WL 
SPRD DURING THE COURSE OF THE EVNG AND THE EXTENT OF THE CNVRGNC 
ALG THE DRYLN.  WRMFNT WAS LCTD FM SRN IL ACRS THE LAKE OF THE 
OZARKS INTO NW MO AT 20Z AND XTNSV LOW CLDS RMND OVR ALL OF THE 
BI-STATE.  STILL ALL THE MDLS INCLUDING THE LAST SVRL RUC RUNS ARE 
INDCG BOTH AN INCRS IN SFC DPTS AND TMPS THRU THE RMNDR OF THE AFT 
AND INTO THE EVNG IN ADVANCE OF EWD SURGING DRYLN.  THIS INCRS IN 
PBL MSTR/HEAT AND GOOD MID LVL CAA RESULTS IN THE MDLS MAINTAINING 
THE SWATH OF UNSTBL AIR WELL PAST SUNSET INTO THE NGT IN ADVANCE OF 
THE STG SYS.  DP LYR SHEAR IS IMPRSV TO SAY THE LEAST WITH LATEST 
LAPS 0-6KM BULK SHEAR AT 70-80 KTS...AND VALUES CLOSE TO THESE SHUD 
BE MAINTAINED DURING THE EVNG AS THE MID LVL JET CONTS TO PROP EWD 
IN ASSOCN WITH THE STG SHRTWV TROF.  THUS SVR THREAT STILL LOOKS 
GOOD IF PROGGED DESTABILIZATION IS INDEED CORRECT.  NATURE TO THE 
FRCG SUGGESTS THAT COVERAGE OF STRMS SHUD BE SCT AND WL WORD AS 
SUCH...ENDING WEST TO EAST DURING THE TNGT PD.

FAIRLY GOOD DRYING BHD THIS SYS AND MDLS ARE ALL NOW A BIT COOLER 
THAN PRVS RUNS FOR SUN/SUN NGT.  HV TRENDED THE NEW FCST DOWNWARD A 
TAD MORE BASICALLY SPLITTING THE DIF IN THE MAV/FWC NUMBS.  WL PRBLY 
SEE SOME WRAP ARND CLDS WORK INTO THE FAR NORTH LATE TNGT AND AT 
LEAST SCT INSTABILITY CU FRM SUN MRNG IN THE CYCLONIC FLOW IN THE 
WAKE OF THE LOW OVR THE NRN/ERN SXNS.  BREEZY AS WELL.

SFC HI BLDS ACRS SUN NGT WITH ANY LINGERING INSTAB CU DSIPTG AND LVG 
MCLR SKIES FOR A WHILE.  MDLS HOWEVER BGN SPRDG WAA CLDS ACRS THE 
NRN HALF OF THE CWFA LATE SUN NGT IN ADVANCE OF A QUICK MVG 
IMPULSE.  HV KEPT THE FCST DRY BUT WL HV TO WATCH TO SEE IF A FEW 
SHRA MAY DVLP FM MID LVL MSTR DECK.  

FM MON AND BYD THE FCST DETAILS BCM LESS CLR.  THE NEW AVN IS MUCH 
DIF THAN THE PRVS RUN AND HAS TRENDED TWDS YDAS CANADIAN AND THE 
LATEST UKMET/ECMWF SHWG MORE NRN STRM AMPLIFICATION AND THUS THE SWD 
FNT PROGRESSION ON MON/MON NGT IS ABT 24H FASTER THAN PRVSLY FCST.  
I HV KEPT SOME POPS GOING WITH IT AND HV TAILORED TMPS A BIT.  THE 
EXACT PSN AND WAVERING IN RSPNS TO SHRTWVS STILL RMNS QUESTIONABLE 
INTO WED.  ATTM AVN SUGGESTS THREAT OF ELEVATED TRW TUE NGT INTO 
ERLY WED THEN SFC BASED STRMS LATE WED/WED NGT WITH SFC WV 
TRANSLATING ALG THE E/W BNDRY.
     
.STL...NONE
GLASS