[LeArc] Forecast Discussion : MLI@ 7/17/2003 3:47:32 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 170841
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
340 AM CDT THU JUL 17 2003

QUIET WEATHER EARLY THIS MORNING OVER FORECAST AREA WITH CONVECTION 
FIRING NOT TOO FAR TO SOUTH AND SOUTHWEST. AT SURFACE...HIGH THAT 
MOVED OVER AREA WEDNESDAY WAS CENTERED OVER NORTHEAST IN. RETURN 
FLOW HAS NOT YET DEVELOPED IN EARNEST AS WARM FRONT WAS STILL TO 
SOUTH...EXTENDING FROM LOW IN SW NEB TO FAR NW MO...THEN SE TO NEAR 
SOUTHERN TIP IL. NOCTURNAL CONVECTION WAS FOCUSED ON THIS SURFACE 
BOUNDARY TONIGHT OVER SE NEB INTO KS AND MO UNDER 00Z POSITION OF 
H85 THETA E RIDGE AXIS. CANADIAN COLD FRONT WAS POISED TO 
NORTH...FROM ABOUT SD/ND BORDER EAST TO LAKE SUPERIOR WITH ON-GOING 
CONVECTION AT ITS EASTERN END. AT UPPER LEVELS...RIDGE AXIS 
REMAINED OVER ROCKIES WITH LOW CHURNING OVER HUDSON BAY REGION. AS 
THIS LOW MOVES SOUTHEAST...THE STRENGTHENING NW FLOW WILL PUSH THE 
NORTHERN FRONT SOUTH INTO CWFA TODAY. MAIN SHORT TERM CHALLENGE IS 
SEVERE POTENTIAL THIS AFTERNOON INTO EVENING AS THIS FRONT MOVES 
INTO POTENTIALLY VERY UNSTABLE AIRMASS.

MODELS SIMILAR IN AGREEMENT WITH VORT MAX IN NW FLOW MOVING INTO WI 
TO PUSH THE SURFACE FRONT SOUTH INTO NORTHERN CWFA BY EARLY 
AFTERNOON. LIKE 06Z META HANDLING OF WARM FRONT PUSHING TO CENTRAL 
IA INTO SE IA AXIS BY EARLY AFTERNOON WITH COLD FRONT TO NORTH NOT 
REALLY ADVANCING MUCH UNTIL EVENING. ALL MODELS WERE IN AGREEMENT 
WITH VERY UNSTABLE AIRMASS AND DEEP MOISTURE POOLING ACROSS THE 
NORTHERN HALF OF THE CWFA THIS AFTERNOON...ESPECIALLY ON IA SIDE. 
OVER EASTERN IA...CAPES PROGGED WELL ABOVE 4000 J/KG...LI/S BELOW -8 
DEG C...AND STEEP LAPSE RATES IN PLACE BY LATE AFTERNOON. HAVE 
RAISED MAX TEMPERATURES UP TO LOWER END OF LATEST GUIDANCE WITH MID 
80S NORTH FAR NORTH TO LOWER 90S SOUTH. LOCAL BLEP TECHNIQUE 
CALCULATIONS SUGGEST POSSIBLE EXTREME WIND EVENT...STRAIGHT LINE 
WINDS WELL OVER 80S KTS...WITH INPUT OF LOW 90S TEMPERATURES AND 
SURFACE DEWPOINTS IN MID TO UPPER 70S OVER EASTERN IA TO SOUTHEAST 
IA IN LATE AFTERNOON AND EARLY EVENING TIMEFRAME. WILL ADD SEVERE 
POTENTIAL TO GRIDS AND ZONE WORDING. IN EVENING...ALL MODELS POINT 
TOWARD MCS OVER SOUTHERN HALF CWA WHICH LOOKS REASONABLE AND HAVE 
RAISED POPS TO LIKELY IN SOUTH AND KEPT SCATTERED IN NORTH...MAINLY 
BEFORE MIDNIGHT.

THE FRONT SETTLES WELL SOUTH OF THE AREA FRIDAY WITH EASTERLY FLOW 
OFF GREAT LAKES HOLDING TEMPS IN 70S EXCEPT FAR SOUTH. FEW CHANGES 
MADE TO GRIDS FRIDAY THROUGH SATURDAY NIGHT WITH DRY FORECAST AND 
MUCH LOWER DEWPOINTS. SIGNIFICANT DIFFERENCES APPEAR BY SATURDAY IN 
LOCATION OF SURFACE HIGH...WITH GFS ESPECIALLY AN OUTLIER WITH THE 
HIGH TOO FAR WEST AND DELAYING RETURN FLOW.   ...SHEETS   

EXTENDED...SUN-THU
FORECAST STILL LOOKS ON TRACK WITH GFS/EURO MODELS ROTATING A 
STRONG MID LEVEL TROF FOR LATE JULY THROUGH THE GREAT LAKES REGION.
TIMING OF FRONT STILL IN QUESTION WITH GFS SLOWER THAN UKMET.  
EVENING/EARLY AFTERNOON FROPA TIMING SUGGESTED BY EITHER MODEL 
BRINGS FRONT THROUGH DURING FAVORABLE TIME OF DAY FOR TSRA.  ABOUT 
THE ONLY ADJUSTMENTS MADE TO THE EXTENDED GRIDS...WAS TO TWEAK 
MONDAYS TEMPS UP A LITTLE.  I DIDN'T GO AS WARM AS THE MEX SUGGESTS 
WITH TIMING ISSUES...BUT GFS WAS HOLDING COOLEST AIR NORTH OF CWA 
UNTIL LATER IN THE DAY.  GFS STILL BRINGING H8 TEMPS AROUND +8C IN 
FOR TUESDAY AND WEDNESDAY.  MEX PROGGING MID 70S FOR HIGHS TUESDAY 
OVER CWA...NOT BAD FOR THE END OF JULY.

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

$$