[LeArc] Forecast Discussion : MLI@ 8/21/02 2:56:53 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 210800
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
300 AM CDT WED AUG 21 2002

SOMEWHAT COMPLICATED SYSTEM THIS MORNING...WITH ONGOING CONVECTION 
EXTENDING FROM SOUTHERN SD...ACROSS IA...CENTRAL IL.  TSTMS 
INITIATED OVER SERN SD EARLIER IN A TOUNGE OF HIGHER DEWPOINTS ALONG 
A SURFACE FRONT THAT 06Z EXTENDED FROM EAST CENTRAL SD...ACROSS SRN 
MN TO JUST SOUTH OF KLSE...AND ALMOST STRAIGHT EAST.  DEWPOINTS 
ACROSS CWA ARE RISING SLOWLY...AND CLOUDS INCREASING AS DEBRIS 
CIRRUS SPREADS SOUTHEAST FROM ONGOING CONVECTION.  850MB LLJ AT 00Z 
WAS DIRECTLY FEEDING INTO AREA WHERE CONVECTION WAS AT THAT 
TIME...AND PROFILERS NOW INDICATE IT HAS VEERED TOWARDS MN WITH 
CONVECTION.  EXPECT THAT STRONG MOISTURE POOL AT 00Z OVER WRN IA HAS 
ALSO SHIFTED EAST.  MISSING DATA ON PLOTS MADE IT HARD TO PICK OUT 
UPPER LEVEL FEATURES...THOUGH GOOD OLD SATELLITE IMAGERY AND 
PROFILERS SHOW A WAVE MOVING ACROSS THE DAKOTAS...AND ANOTHER MOVING 
ACROSS KS/OK BORDER AREA.

00Z MODELS ONCE AGAIN HAVING DIFFICULTIES AGREEING ON TIMING... 
PLACEMENT...AND THERE ARE SOME PROBLEMS WITH CONVECTIVE FEEDBACK 
ALSO.  GIVEN THIS...WILL BE CONSERVATIVE WITH FORECAST.  ETA APPEARS 
TO HAVE BEEN MISSING SOME INITIALIZATION DATA...AS IT IS FAR TOO 
WEAK WITH THE JET MAX OVER THE GREAT LAKES...ONLY 80-90 KTS...VS THE 
100+ KTS ON MN/CAN BORDER AREA ACCORDING TO AIRCRAFT DATA.  WHILE 
THE ETA INTENSIFIES THIS JET BY 06Z...SOMETHING UNREALISTIC MUST 
HAVE OCCURRED TO MAKE THIS OCCUR.  THE AVN PICKS UP ANOTHER LOVELY 
CONVECTIVE FEEDBACK BULLSEYE THURSDAY NIGHT...AND RUNS IT ACROSS THE 
FA FRIDAY NIGHT.  SO...HAVE DOUBTS ABOUT AVN FCST FRI 12Z AND 
BEYOND.  VORT MAX AND HEIGHT FIELDS LOOK OVERDONE ALSO...THOUGH 
SOMETHING WEAKER IS A BIT MORE LIKELY.  KIND OF PREFER NGM 
SOLUTION...WHILE IT DOES NOT QUITE CAPTURE THE ABOVE JET WELL...IT 
DOES BETTER THAN THE ETA WITH IT...AND WILE DOES NOT GO INTO 
FRIDAY...IS NOT AS STRONG WITH OMEGA BULLSEYE AT 48HRS. 

TODAY AND TONIGHT...WILL HAVE TO WATCH RADAR TRENDS FOR ANY MORNING 
CONVECTION...BUT HAVE DOUBTS.  MAIN TSTM THREAT WILL BE LATE THIS 
AFTERNOON...AND FURTHER WEST. MODELS ACTUALLY AGREE ON BRINGING  
PRECIP TO IA PART OF CWFA BY 00Z.  TIMING IS GOING TO BE FAVORABLE 
FOR SEVERE WX...AND WE ARE OUTLOOKED BY SPC FOR SLIGHT RISK.  DONT 
ANTICIPATE MUCH OF A CAP...AND INSTABILITY SHOULD BE HIGH...SO WILL 
MENTION POSSIBILITY OF SEVERE WEST OF MISSISSIPPI IN THE AFTERNOON 
AND EAST OF THE MISSISSIPPI IN THE EVENING. DAY SHIFT CAN REFINE AS 
THINGS DEVELOP.  HIGH TEMPS MAY BE HELD DOWN AGAIN WITH CLOUD 
COVER...BUT COMPRESSION AHEAD OF FRONT...WILL BRING TEMPS INTO THE 
MID 80S TO AROUND 90.  GOING TEMPS ARE VERY CLOSE TO THIS...AND MAY 
ONLY TWEAK.  LOWS TONIGHT IN GOING FCST SIMILAR TO AVAILABLE 
GUIDANCE...AND AGAIN WILL ONLY TWEAK.

THURSDAY AND THURSDAY NIGHT...THOUGH MODELS CANNOT AGREE ON POSITION 
OF FRONT...FEEL BEST POPS WILL BE TO SOUTHERN PARTS OF CWA AS FRONT 
SLOWLY SAGS SOUTH.  BUT HIGH CHANCE POPS SOUTH AND SLIGHT CHANCE 
NORTH DURING THE DAY. AT NIGHT...LOW LIKELY SOUTH...TAPERING TO LOW 
CHANCE NORTH.  DO NOT INTEND TO CHANGE TEMPS MUCH.  IF MODELS KEEP 
PUSHING FRONT TO SOUTH ON NEXT RUN...MAY NEED TO REDUCE POPS ACROSS 
CWA FOR THURSDAY NIGHT.  

NO CHANGES ANTICIPATED TO FRI-TUE TIME FRAME.

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

LRE