MESOSCALE DISCUSSION 0621 NWS STORM PREDICTION CENTER NORMAN OK 1116 AM CDT THU APR 10 2008 AREAS AFFECTED...PORTIONS EXTREME SERN MO...SRN/ERN IL...WRN INDIANA. CONCERNING...HEAVY RAINFALL VALID 101616Z - 101845Z BAND OF TSTMS -- MOVING NEWD 40-50 KT ACROSS PORTIONS SRN IL AND SERN MO AS OF 16Z -- IS EXPECTED TO MOVE NEWD ACROSS REMAINDER DISCUSSION AREA DURING NEXT 2-3 HOURS. ALTHOUGH SVR POTENTIAL SHOULD CONTINUE TO DIMINISH AS THIS ACTIVITY MOVES OVER RELATIVELY STABLE SFC AIR MASS...MOISTURE/LIFT/INSTABILITY ABOVE SFC WILL FAVOR CONTINUING HEAVY RAIN. RATES 1-2 INCHES/HOUR SHOULD BE COMMON AS THIS ACTIVITY MOVES OVERHEAD. VWP/PROFILER DATA SHOWS STRENGTHENING/50-70 KT LLJ ACROSS THIS REGION...WHICH HAS BEEN INTENSIFYING IN RESPONSE TO NWD EJECTION OF OCCLUDING DEEP-LAYER CYCLONE IN CENTRAL PLAINS. STRONGEST FLOW ABOVE BOUNDARY LAYER LIKEWISE WILL CONTINUE TO SHIFT NEWD ACROSS LOWER OH VALLEY AND INDIANA...ACCOMPANIED BY STG MOIST ADVECTION...ISENTROPIC LIFT AND MOISTURE TRANSPORT. GPS PW...MODIFIED RAOBS AND MODEL SOUNDINGS INDICATE AROUND 1.5 INCH PW ALREADY PRESENT IN PRE-STORM ENVIRONMENT. RUC FCST SOUNDINGS INDICATE BUOYANCY WILL BE INCREASINGLY ELEVATED ABOVE SFC WITH NEWD EXTENT...BUT STILL FAVORABLE FOR TSTM -- WITH MUCAPE VALUES INCREASING TO 250-500 J/KG NEAR IL/INDIANA BORDER DURING 18-19Z TIME FRAME. ..EDWARDS.. 04/10/2008 ATTN...WFO...IWX...IND...PAH...LOT...ILX...LSX...