968 
FXUS63 KLSX 121915
AFDSTL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
215 PM CDT MON AUG 12 2002

FORECAST CHALLENGE DEALS WITH PCPN CHCS THE NEXT FEW DAYS.  CURRENT 
ZONES HAVE A GOOD HANDLE ON FORECAST AND WILL ONLY REQUIRE MINOR 
CHANGES.  AVN/ETA INITIALIZED FAIRLY WELL AND ARE IN PRETTY GOOD 
AGREEMENT THROUGH 60 HOURS.  

SCT TSRA DEVELOPED RAPIDLY THIS AFTN IN AREA OF -6 TO -9 LIS WITH 
SMALL CINH.  TSRA DEVELOPMENT AIDED BY MODEST MID LVL SYNOPTIC SCALE 
ASCENT AHEAD OF S/W TROF CURRENTLY OVR MO/KS BORDER.  THINK THERE 
SHOULD BE A DIMINISHING TREND BY LATE THIS EVENING WITH LOSS OF 
HEATING AND VORT MOVG EWD...BUT SHOULD INCREASE AGAIN LATER TONIGHT. 

BEST CHC FOR PCPN WILL BEGIN LATER TONIGHT AS UVV INCREASE GREATLY 
IN NRN AND WRN ZONES AHEAD OF NEXT TROF.  THIS TREND WILL CONT 
AREAWIDE THRU TUES NIGHT AS CWA LIES UNDER UPR DIV IN RIGHT ENTRANCE 
OF JET STREAK AND MID LVL UVV SEEN IN 500-700 Q-VEC CONV.  DECENT 
CONV EXPECTED ALG SLOW MOVING CDFNT AS IT BECOMES MORE PARALLEL TO 
UPR FLOW.  GOING ZONE TREND OF MOVING BEST CHC AXIS FROM NW TO SE 
ACROSS AREA STILL LOOKS GREAT...BUT MAY NEED TO BUMP UP SOME AREAS 
TO CAT POPS. FFG IS QUITE HIGH OVR MOST OF THE CWA... THOUGH WILL 
MENTION LOCALLY HEAVY RAINFALL IN WRN AND NRN ZONES TONIGHT AS 
STORMS SHOULD BE SLOW MOVING WITH PWS AOA 1.75 INCHES.  TROF AXIS 
MOVES E OF AREA ON WED AND WILL KEEP MORNING POPS IN S AND E.

WL USE A BLEND OF TMOS GUIDANCE ON TEMPS. 

SERIES OF FAST MOVING S/W TROFS IS FORECAST TO MOVE THRU FAIRLY 
ZONAL FLOW OVER THE NRN CONUS DURING THE EXTENDED PERIOD (FRI-MON).  
MEDIUM RANGE MODELS ARE HAVING DIFFICULTY WITH THE TIMING OF THESE 
TROFS.  12Z AVN STILL BRINGS HI 1000-500MB RH/QPF ACROSS REGION ON 
FRI...SO WILL KEEP CHC TSRA GOING.  FRONT THAT WAS PROGGED TO STALL 
OVR AREA ON SUN IS NOW MOVING INTO MO/IL A DAY LATER...SO WILL MOVE 
CURRENT CHC ON SUN TO MON.  MRF MOS TEMPS ARE LINE UP WELL WITH 
850MB TEMPS SO WILL FOLLOW CLOSELY.     

.STL...NONE

BRITT