ZCZC SPCSWOMCD ALL ACUS11 KWNS 241937 SPC MCD 241937 INZ000-242330- MESOSCALE DISCUSSION 0326 NWS STORM PREDICTION CENTER NORMAN OK 0237 PM CDT SUN MAR 24 2013 AREAS AFFECTED...CNTRL INDIANA CONCERNING...HEAVY SNOW VALID 241937Z - 242330Z SUMMARY...HEAVY SNOW WILL OVERSPREAD CNTRL INDIANA DURING THE MID/LATE AFTERNOON HOURS -- PRIMARILY AFTER 2030Z -- WITH RATES OF 1 TO LOCALLY 2 IN/HR LIKELY. DISCUSSION...BANDS OF HEAVY SNOW WILL DEVELOP EWD/ENEWD FROM CNTRL IL AND OVERSPREAD CNTRL INDIANA AFTER 2030Z. THIS SNOW IS IN ASSOCIATION WITH STRONG DEEP ASCENT TO THE N OF A MID-LEVEL JET MAX/DRY SLOT THAT IS SURGING EWD THROUGH THE LOWER OH VALLEY AND MID SOUTH. N OF THIS FEATURE...ASCENT ACCOMPANYING MODEST FRONTOGENETIC CIRCULATIONS WILL AUGMENT STRONG DCVA AT THE ENTRANCE REGION OF THE JET MAX TO MAINTAIN EFFICIENT PRECIP GENERATION. THIS WILL ESPECIALLY BE THE CASE AS GPS DATA INDICATE 0.5-0.7-INCH PW VALUES EXTENDING INTO THE REGION WITHIN A WARM CONVEYOR BELT THAT LEADS THE JET MAX/DRY SLOT. WHILE LOW-LEVEL THERMAL PROFILES ARE INITIALLY WARM FOR SNOW...ESPECIALLY ALONG AND SOUTH OF THE INTERSTATE 70 CORRIDOR...ADIABATIC COOLING ASSOCIATED WITH THE FORCED ASCENT COMBINED WITH LOW-LEVEL EVAPORATIVE COOLING WILL ALLOW WET-BULB ZERO HEIGHTS TO QUICKLY DESCEND SUFFICIENTLY TO SUPPORT HEAVY SNOW SUCCEEDING THE ONSET OF PRECIP. FORECAST SOUNDINGS SUGGEST THAT THE STRONG ASCENT WILL BE SUPERIMPOSED WITH SATURATED DENDRITIC GROWTH ZONES WITHIN THE 600-500-MB LAYER TO SUPPORT EFFICIENT SNOW GROWTH. SNOW RATES OF 1 TO LOCALLY 2 IN/HR WILL BE LIKELY...AND AN ISOLATED LIGHTNING STRIKE OR TWO CANNOT BE RULED OUT IN ASSOCIATION WITH THE HIGHEST...CONVECTIVELY ENHANCED SNOW RATES. SUCH RATES ARE ALSO SUPPORTED BY THE MULTI-MODEL CONSENSUS AMONGST THE LATEST HIGH-RESOLUTION WRF GUIDANCE. THE HEAVY SNOW...WITH SIMILAR RATES...WILL LIKELY CONTINUE INTO THE EVENING HOURS AS ASCENT ACCOMPANYING THE DEFORMATION ZONE N/NW OF THE MID-LEVEL CYCLONE TRACKS ACROSS THE REGION. ..COHEN.. 03/24/2013 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...ILN...IWX...IND...LOT... LAT...LON 39268595 39198689 39438746 39788711 40148700 40488718 40878685 40838616 40568531 40198511 39658526 39268595 NNNN