MESOSCALE DISCUSSION 0114
   NWS STORM PREDICTION CENTER NORMAN OK
   1049 AM CST SUN FEB 20 2011
   
   AREAS AFFECTED...FAR SOUTHERN MN/FAR NORTHERN IA AND SOUTHERN WI TO
   SOUTHERN LOWER MI AND EXTREME NORTHERN INDIANA/OH
   
   CONCERNING...WINTER MIXED PRECIPITATION 
   
   VALID 201649Z - 202045Z
   
   A RELATIVELY NARROW CORRIDOR OF MIXED PRECIPITATION...TYPICALLY
   AROUND 50-75 MILES IN NORTH-SOUTH EXTENT...WILL EXPAND NORTH AND
   EASTWARD FROM FAR SOUTHERN MN/FAR NORTHERN IA AND SOUTHERN WI INTO
   SOUTHERN LOWER MI AND THE IMMEDIATELY ADJACENT PORTIONS OF EXTREME
   NORTHERN INDIANA/OH. FREEZING RAIN AND SLEET ARE LIKELY FOR A
   SEVERAL HOUR DURATION...ALONG WITH THE POSSIBILITY OF
   ISOLATED/EMBEDDED TSTMS.
   
   CONSIDERABLE LOW LEVEL WARM ADVECTION/ISENTROPIC LIFT REGIME WILL
   CONTINUE TO SUPPORT A NORTH AND EASTWARD EXPANSION OF ONGOING MIDDAY
   PRECIPITATION ACROSS THE UPPER MS VALLEY/LAKE MI GENERAL
   VICINITY...INCLUDING FAR SOUTHERN MN/FAR NORTHERN IA AND SOUTHERN WI
   TO SOUTHERN LOWER MI AND IMMEDIATELY ADJACENT PORTIONS OF
   INDIANA/OH. WHERE NEAR-SURFACE TEMPERATURES REMAIN AROUND/BELOW
   FREEZING WITHIN THIS CORRIDOR...MIXED PRECIPITATION INCLUDING
   FREEZING RAIN/SLEET WILL DEVELOP/CONTINUE TO OCCUR OWING TO A
   PARTIAL/FULL MELTING LAYER ALOFT GENERALLY AROUND 1.5-2.5 KM AGL.
   PROXIMITY OF SLANTWISE/WEAK UPRIGHT BUOYANCY WILL CONTRIBUTE TO THE
   POSSIBILITY OF ISOLATED/EMBEDDED TSTMS...AND OTHERWISE YIELD
   CONVECTIVELY ENHANCED PRECIPITATION RATES THROUGH THE AFTERNOON. THE
   STRENGTH OF THE WARM ADVECTION REGIME WILL 1/ GENERALLY KEEP
   TEMPERATURES ONLY MARGINALLY AROUND FREEZING IN MOST LOCALES AND 2/
   RESULT IN A TRANSITION TO RAIN ON THE SOUTHERN PERIPHERY OF THE
   AFOREMENTIONED CORRIDOR. NONETHELESS...AT LEAST A LIGHT ICE GLAZE IS
   POSSIBLE FROM FREEZING RAIN...AS WELL AS SLEET...THIS AFTERNOON
   WITHIN A TRANSITIONAL/SPATIALLY NARROW CORRIDOR.
   
   ..GUYER.. 02/20/2011
   
   
   ATTN...WFO...DTX...IWX...GRR...MKX...ARX...MPX...DMX...FSD...
   
   LAT...LON   43889577 44089278 44009030 43318629 42598389 41938385
               41668486 42408625 42928776 43279474 43889577