[LeArc] Forecast Discussion : MLI@ 7/18/02 2:50:13 AM

[learc@mailman.qth.net]

The following weather message is provided by McDonough County E.S.D.A.


FXUS63 KDVN 180750
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
250 AM CDT THU JUL 18 2002

ISOLATED TSRA OVER WESTERN SECTIONS OF CWA BEGINNING TO REALLY LOSE 
STRENGTH.  IT WAS AROUND THIS TIME YESTERDAY MORNING THAT OTHER TSRA 
N OF UPPER LOW CENTER DIED.  EXPECT NEW DEVEOPMENT TO BEGIN IN NW 
IA/SE SD/NE NEB...IN THE SHEAR ZONE APPARENT ON IR SATELLITE 
EXTENDING FROM NE NEBRASKA TO NRN WI...AND WHERE THERE IS AN OLD 
OUTFLOW BOUNDARY TO FOCUS ON.  UPPER LEVEL ANALYSIS INDICATING THAT 
PESKY UPPER LEVEL LOW OVER NE MO...STILL NO COHERENT FALLS TO 
INDICATE THAT IT WILL MOVE OUT IN THE NEXT 24 HOURS.  

MAIN CONCERNS THIS MORNING INCLUDE MOVEMENT OF THIS FRONT THROUGH 
SATURDAY...AND ACCOMPANYING PRECIPITATION CHANCES.  

00Z MODELS FINALLY COMING IN LINE WITH EACH OTHER ON THE HANDLING OF 
THE UPPER LOW THROUGH THE WEEKEND...SLOWLY PHASING IT WITH THE MAIN 
FLOW AND SHIFTING IT TO THE EAST.  MODELS ALSO IMPROVING ON HANDLING 
OF SURFACE FRONT TODAY AND TONIGHT...BUT STILL SOME SIGNIFICANT 
DISAGREEMENT IN POSITION FOR FRIDAY AND SATURDAY.  IN THE NEAR 
TERM...PREFER HOW THE ETA DEVELOPS QPF THIS MORNING...WITH THE AVN 
OVERDOING CURRENT ISOLATED CONVECTION OVER IA.  AS FAR AS THE 
FRONT...BOTH MODELS SEEM TO HAVE A REASONABLE HANDLE ON ITS POSITION 
AT 06Z.  ETA BRINGS DOWN FIRST WHAT LOOKS LIKE AN OUTFLOW BOUNDARY 
IN TO NORTHERN CWA THIS MORNING...AND THEN BRINGS IN THE MAIN FRONT 
TO CATCH IT UP AROUND MID-DAY AND SHIFTS SLOWLY SOUTH FROM THERE.  
ETA DOES NOT HAVE ANY QPF WITH THIS BOUNDARY...BUT BY 18Z FEEL THAT 
IT HAS A MUCH BETTER FRONTAL POSITION THAN AVN WHICH STILL HAS IT 
ACROSS SRN MN.  CONVECTION WITH CURRENT ND MCS SHOULD HELP PUSH THIS 
FRONT SOUTH AS IT FOLLOWS THE THICKNESSES.  BY TONIGHT THE FRONT 
SHOULD SIT ACROSS SOUTHERN CWA...WHICH IS BETTER DEPICTED IN 
ETA...THOUGH AVN ALSO HINTS AT THIS.  FRONT MOVES SOUTH TO JUST 
SOUTH OF CWA ON FRIDAY...AND THIS IS WHERE THE MODELS BEGIN TO 
DIVERGE.  ETA DEVELOPS A NEW LOW CENTER FRIDAY NIGHT OVER EASTERN 
WY...WITH THE AVN DEVELOPING A SIMILAR FEATURES MUCH FURTHER NORTH.  
THE ETA TURNS OUR FRONT IN TO A WARM FRONT...WITH THE AVN GRADUALLY 
WASHING IT OUT. THE UPSHOT IS THAT WE ARE GOING TO NEED LOW POPS IN 
THE FORECAST AT LEAST FOR THE SOUTHERN PART OF THE CWA FRIDAY NIGHT 
AND SATURDAY.  

EXTENDED(SUN-WED) 
ONLY CHANGE EXPECTED AT THIS TIME IS TO REMOVE LATE WORDING FROM 
TSRA WORDING ON SUNDAY.  THIS SYSTEM IS MOVING IN FASTER THAN 
PREVIOUSLY THOUGHT...AND AVN HAS BEEN GRADUALLY SPEEDING THIS SYSTEM 
UP SO THERE IS AT LEAST A LITTLE CONTINUITY.  OTHERWISE...NO CHANGES 
EXPECTED ATTM.

.DVN...
IA...NONE.
IL...NONE.
MO...NONE.

LRE