[LeArc] Forecast Discussion : MLI@ 6/10/2003 3:19:33 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 102015
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
312 PM CDT TUE JUN 10 2003

FINE LINE OF CONVECTION SEEN ON VISIBLE SATELLITE IMAGERY AND 88D 
FROM FREEPORT THROUGH KDVN INTO FAR SOUTHEAST IOWA OCCURRING ALONG 
SURFACE TROUGH EXTENDING FROM LOW JUST NORTH OF KLSE. ONLY SPRINKLES 
OCCURRED WITH PASSAGE AT OFFICE...BUT RADAR TRENDS SHOW CONVECTION 
MAY BE TAKING OFF...INITIALLY OVER NORTHWEST IL...AS IT MOVES INTO 
LOW LEVEL THETA E RIDGE AND WHERE BREAKS OF SUNSHINE HAS PUSHED LAPS 
SB CAPES INTO RANGE OF 1000 TO 2000 J/KG. 18Z ANALYSIS INDICATED 
MAIN COLD FRONT JUST ENTERING CWA IN EASTERN IOWA... EXTENDING 
SOUTHWEST TO EASTERN KS. SHORT TERM FORECAST CHALLENGE IS 
THUNDERSTORM CHANCES THIS EVENING...THEN TEMPERATURES.

AREA OF SCATTERED POPS IN GRIDS LOOKED TO HAVE A GOOD HANDLE ON AREA 
OF DEVELOPING CONVECTION NEXT SEVERAL HOURS AND WILL KEEP 30 PERCENT 
GOING. CANNOT RULE OUT A FEW SHOWERS ALONG COLD FRONT AND HAVE 
INTRODUCED SLIGHT CHANCE POPS FOR ALL BUT NORTHWEST CORNER OF  
FORECAST AREA. 3 HOUR PRESSURE FALLS MAX OF 2 TO 3 MB OVER EASTERN 
WI INTO WESTERN LOWER MI INDICATING THAT THE SURFACE LOW SHOULD 
CONTINUE EAST AS ADVERTISED BY SHORT TERM MODELS WITH HIGH CURRENTLY 
OVER ND SHIFTING EAST. MOST CU WEST OF LOW LOOKS DIURNAL...HOWEVER 
SATELLITE SHOWS SOME BANDS OF SC ACROSS SOUTHERN MN THIS AFTERNOON 
AND ANTICIPATE SOME TO LINGER WELL INTO MIDNIGHT UNTIL LOCAL FLOW 
BECOMES LESS CYCLONIC. SURFACE AIRMASS TRAJECTORY SUPPORTS CLOSE TO 
GOING GRIDS AND LATEST GFS MOS LOWS. WEDNESDAY...FLOW IS NEARLY 
ZONAL AT H5 WITH SHORTWAVE LIFT WELL TO SOUTH ALONG FRONT POSSIBLY 
BRUSHING FAR SOUTHERN CWFA WHERE SLIGHT POPS FOR SHOWERS INTRODUCED. 
OTHERWISE... PARTLY CLOUDY WITH EASTERLY SURFACE FLOW AROUND HIGH TO 
NORTH SUPPORTING HIGHS CLOSER TO COOLER MAV GUIDANCE. 

FURTHER OUT (WED NIGHT THROUGH TUESDAY)
AS STATED IN THE PREVIOUS AFD...MODELS ARE HAVING TROUBLE RESOLVING 
SYNOPTIC SITUATION THROUGH THE PERIOD.  IN ALL...THE LOCAL AREA WILL 
BE ON THE SOUTHERN EDGE OF AN ACTIVE WESTERLY FLOW AT MID LEVELS 
THROUGH EARLY THURSDAY.  SOUTH OF THIS FLOW...A CHAOTIC MIX OF LOW 
LEVEL CIRCULATIONS AND STALLED FRONTS WILL PERSIST.  AT THIS 
TIME...WILL CONTINUE TREND OF GOING FORECAST AND KEEP THIS FRONT 
SOUTH OF THE AREA THROUGH THURSDAY MORNING.  WE BELIEVE THIS FRONTAL 
PLACEMENT WILL BE CRITICAL THROUGH THE ENTIRE FORECAST PERIOD AS 
HEAVY RAINS AND RESULTANT STREAM FLOODING WILL OCCUR WHERE EVER IT 
IS FOUND. THE GREATEST THREAT APPEARS TO BE SOUTH OF THE CWA INTO 
MISSOURI AND CENTRAL/SOUTHERN ILLINOIS THROUGH THURSDAY.  THE ETA 
AND GFS DIVERGE SIGNIFICANTLY WITH THE PLACEMENT OF THE SFC AND 
850MB BOUNDARIES BEYOND 60 HOURS.  WITH OTHER EXTENDED MODELS 
SUPPORTING BRINGING THE MAIN SYNOPTIC BOUNDARY NORTHWARD SLOWLY 
WEDNESDAY NIGHT AND THURSDAY...WILL MAINTAIN CHANCE POPS THURSDAY 
EVENING AND FRIDAY.  LATEST GFS SOLUTION HOLDS THE MAIN UPPER LOW 
NEAR DES MOINES THROUGH SATURDAY.  TO SAY THE LEAST...CONFIDENCE IS 
LOW FOR ANY MODEL IN THIS WEAK FLOW REGIME THE LATTER HALF OF THE 
WEEK.  THE THREAT FOR HEAVY RAIN STILL EXISTS FOR A PORTION OF THE 
MID MISSISSIPPI VALLEY...BUT FURTHER REFINEMENT OF THE AREA MOST AT 
RISK WILL HAVE TO WAIT AT LEAST ANOTHER DAY.   


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

SHEETS/ERVIN

$$