[LeArc] Forecast Discussion : MLI@ 6/3/2002 2:46:42 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 031942
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
243 PM CDT MON JUN 3 2002

ELEVATED SHOWERS AND FEW TSRA ACROSS NORTHERN HALF CWFA HELPED ALONG 
BY MID LEVEL VORT MAX SEEN ON 88D LOOPS MOVING INTO NE IA AT 18Z. 
VISIBLE IMAGERY SHOWS LARGE AREA FULL SUNSHINE MOST OF DAY SO FAR 
FROM I-80 SOUTH BUILDING HIGH SURFACE INSTABILITY. THIS HAS RESULTED 
IN 30 DEGREE N TO S TEMPERATURE GRADIENT WITH RAIN COOLED...GREAT 
LAKES AIRMASS IN 50S NORTH AND 90S WITH DEWPOINTS IN 70S IN FAR 
SOUTH AT 18Z. KDVN SHOWS E-W OUTFLOW BOUNDARY...NOW LIKELY SYNOPTIC 
FRONT...ABOUT 25 MI S OF RDA AND INCHING SLOWLY N. WITH BOUNDARY 
CONTINUING TO BISECT AREA THROUGH TUESDAY...TIMING AND PLACEMENT OF 
HIGHEST TSRA POTENTIAL AND TRYING TO GET CLOSE TO REALITY WITH LARGE 
TEMPERATURE GRADIENT MAIN FORECAST CHALLENGES.

INITIAL CONCERN WILL BE LATE AFTERNOON SEVERE POTENTIAL AS H7 WAVE 
SEEN ON PROFILER NETWORK PUSHES INTO SW...THEN CENTRAL IA AND MAY 
INITIATE SURFACE BASED CONVECTION ALONG FRONT WHERE CAP WILL BE 
WEAKEST IN E-SE IA. WILL LEAVE OUT SEVERE WORDING FOR NOW SINCE MUCH 
UNCERTAINTY IN WHERE AND WHEN CONVECTION WILL INITIALIZE. MORE 
WIDESPREAD MCS EXPECTED TO FORM WELL N OF FRONT AS HAPPENED PAST FEW 
NIGHTS AND TRACK E THEN SE. WILL KEEP LIKELY POPS GOING IN NORTHERN 
2/3RDS WITH MENTION OF LOCALLY HEAVY RAINFALL AND CHANCE TSRA FOR 
FAR SOUTH OVERNIGHT. FORCING TO AID CONVECTION LOOKS BETTER TONIGHT 
THAN PAST FEW DAYS WITH IMPRESSIVE SHORTWAVE SEEN ON WV IMAGERY 
MOVING INTO SW KS UNDERPLAYED BY MODELS WILL LIKELY PLAY ROLE IN 
LATE EVENING MCS DEVELOPMENT IN NE NEB/NW IA. MODELS SHOW H5 POS 
VORTICITY CENTERS TAKING MORE SRLY PATH THAN LAST NIGHT AND 
ANTICIPATE TRACK AT LEAST INTO NRN ZONES. HEAVY RAIN POTENTIAL 
CONTINUES...ESPECIALLY LATE TONIGHT AND EARLY TUESDAY WITH H85 FLOW 
BECOMING PARALLEL TO LOW LEVEL BOUNDARY AND UPPER LEVEL FLOW. 

ALL MODELS AGREE ON BIG PICTURE WITH WESTERN H5 TROUGH MOVING 
THROUGH WEDNESDAY PRECEDED BY SURFACE CYCLONE CURRENTLY OVER WESTERN 
KS PASSING TO S EARLY WED TO END RAIN CHANCES. DO THINK ETA HAS 
BETTER QPF PLACEMENT TONIGHT FURTHER N...WHEREAS AVN TOO FAR S INTO 
CAPPED WARM SECTOR. THIS COULD SHIFT IF SIGNIFICANT EVENING 
CONVECTION PUSHES SURFACE FRONT BACK SOUTH. 

WILL KEEP LIKELY POPS GOING THROUGH TUESDAY EXCEPT IN FAR S...THEN 
LIKELY ALL ZONES TUESDAY NIGHT AS MAIN LOW RIDES ALONG FRONT TO 
SOUTH AND THEN SWEEPS IT EASTWARD. WARMER FWC HIGHS PREFERRED... 
EXCEPT IN FAR N AND NE...WHERE CLOUDS AND REENFORCING E-NE SURFACE 
FLOW TO KEEP TEMPS NEAR TO BELOW GUIDANCE. 

EXTENDED...MODEL CONCENSUS IS SURFACE HIGH THURSDAY...THEN FLAT 500H 
RIDGING/ZONAL FLOW FRIDAY INTO EARLY SATURDAY. MRF BRINGS SURFACE 
AND UPPER LOWS ALONG US/CAN BORDER SATURDAY NIGHT AND SUNDAY WITH 
FROPA FOR SHOWER CHANCES. WILL KEEP CHANCES GOING INTO MONDAY AS 
TIMING OF UPPER WAVE PASSAGE TO NORTH MAY KEEP INSTABILITY SHOWERS 
GOING. ONLY MINOR CHANGES MADE TO MOS TEMPERATURES.

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

DLS