MESOSCALE DISCUSSION 0017
   NWS STORM PREDICTION CENTER NORMAN OK
   0617 PM CST SAT JAN 12 2013
   
   AREAS AFFECTED...NWRN INDIANA...NRN/CNTRL/W-CNTRL IL...PARTS OF
   E-CNTRL/SERN/S-CNTRL MO
   
   CONCERNING...WINTER MIXED PRECIPITATION 
   
   VALID 130017Z - 130615Z
   
   SUMMARY...WINTER MIXED PRECIPITATION WILL INCREASE IN COVERAGE AND
   INTENSITY THIS EVENING. THIS WILL INCLUDE THE THREAT FOR FREEZING
   RAIN WITH RATES OF 0.05 TO 0.10 IN/HR...WITH LOCALLY HIGHER RATES
   ALSO POSSIBLE. FREEZING RAIN WILL BECOME INCREASINGLY LIKELY IN THE
   CHICAGO AND ST. LOUIS AREAS AFTER 04Z.
   
   DISCUSSION...A LARGE SHIELD OF CONVECTIVE-DEBRIS-RELATED
   PRECIPITATION WITHIN A WARM CONVEYOR BELT WILL CONTINUE TO
   OVERSPREAD THE AREA THIS EVENING. THIS ACTIVITY SHOULD PERSIST THE
   OVERNIGHT HOURS AS ELEVATED WARM ADVECTION OCCURS THROUGH THE
   NIGHT...WITH A TENDENCY FOR HIGHER PRECIPITATION RATES TO SHIFT NEWD
   IN TANDEM WITH THE STRONGER ASCENT.
   
   AS SUBFREEZING SFC-LAYER TEMPERATURES UNDERCUT THE ELEVATED WARM
   ADVECTION...THE LEADING EDGE OF WINTER MIXED PRECIPITATION WILL
   ADVANCE ESEWD ACROSS THE REGION. IMMEDIATELY BEHIND THIS LEADING
   EDGE...A 40-70-MILE WIDE CORRIDOR OF POTENTIAL FREEZING RAIN WILL BE
   ASSOCIATED WITH LIQUID-EQUIVALENT RATES OF 0.05-0.10 IN/HR. LOCALLY
   HIGHER RATES MAY OCCUR OWING TO A MODEST CONVECTIVE ENHANCEMENT
   ASSOCIATED WITH NARROW ELEVATED CAPE PROFILES. THE FREEZING-RAIN
   CORRIDOR WILL LIKELY MOVE INTO NWRN INDIANA BY 07Z.
   
   SENSIBLE HEAT FLUXES ASSOCIATED WITH PREVIOUSLY FALLEN LIQUID MAY
   INITIALLY DELAY THE ONSET OF ICING ON MANY SURFACES...ASIDE FROM
   ELEVATED/METAL SURFACES. REGARDLESS...OBSERVATIONS UPSTREAM ACROSS
   CNTRL MO INTO NERN OK INDICATE PERSISTENT FREEZING RAIN
   OCCURRING...AND SFC ICING WILL BE LIKELY.
   
   TO THE WNW OF THE FREEZING-RAIN CORRIDOR...DEEPER COLD AIR WILL
   LIMIT/PRECLUDE MELTING OF DESCENDING HYDROMETERS AND SUPPORT SLEET
   AND LIGHT TO OCCASIONALLY MODERATE SNOW. REMAINING PRECIPITATION
   WILL PROGRESSIVELY TRANSITION TO SLEET/SNOW FROM WNW TO ESE DURING
   THE OVERNIGHT HOURS...ESPECIALLY ACROSS NRN IL. PRECIPITATION RATES
   ARE EXPECTED TO DECREASE AREA-WIDE BY 09Z AS STRONGER FORCING FOR
   ASCENT SHIFTS NE OF THE AREA.
   
   PLEASE REFERENCE MCD 16 FOR ADDITIONAL DETAILS REGARDING ONGOING
   WINTER MIXED PRECIPITATION ACROSS NERN OK...SERN KS...CNTRL MO...AND
   W-CNTRL IL.
   
   ..COHEN.. 01/13/2013
   
   
   ATTN...WFO...PAH...LOT...ILX...LSX...DVN...SGF...
   
   LAT...LON   42428783 41838762 41628732 41668710 41638697 41398697
               41168716 40538755 39478833 38798905 37649004 36759171
               36519342 36659386 36919364 37599270 38429166 39459025
               40098976 40779025 41449012 41868981 42368904 42428783