MESOSCALE DISCUSSION 0180
   NWS STORM PREDICTION CENTER NORMAN OK
   1149 PM CST WED FEB 20 2013
   
   AREAS AFFECTED...NERN TX PANHANDLE...ERN OK PANHANDLE...NWRN AND
   N-CNTRL OK...SRN KS
   
   CONCERNING...WINTER MIXED PRECIPITATION 
   
   VALID 210549Z - 211145Z
   
   SUMMARY...INCREASING PRECIPITATION RATES...WITH PREDOMINANTLY MIXED
   P-TYPES INITIALLY...ARE FORECAST THROUGH EARLY THU MORNING. A
   TRANSITION TO HEAVY SNOWFALL MAY OCCUR IN A SW-NE CORRIDOR FROM THE
   NERN TX PANHANDLE INTO S-CNTRL KS...WHILE A MORE UNCERTAIN/MIXED
   P-TYPE IS LIKELY ACROSS NWRN AND N-CNTRL OK.
   
   DISCUSSION...STRONG ASCENT ASSOCIATED WITH UPPER DIVERGENCE AHEAD OF
   A SWRN CONUS UPPER TROUGH IS OVERSPREADING RICHER TROPOSPHERIC
   MOISTURE ACROSS THE SRN HIGH PLAINS...RESULTING IN AN INCREASE IN
   PRECIPITATION /PER RECENT RADAR LOOPS/. THIS TREND IS EXPECTED TO
   CONTINUE...WITH WIDESPREAD PRECIPITATION DEVELOPING ACROSS THE ERN
   TX/OK PANHANDLES AND INTO WRN OK...AS THE AFOREMENTIONED LIFT
   BECOMES JUXTAPOSED WITH ISENTROPIC ASCENT FOCUSED WITHIN THE 300-306
   K LAYER. 
   
   THE SFC FREEZING LINE...POSITIONED FROM 40 ESE GUY TO 30 E AVK PER
   05Z OBSERVATIONS...IS FORECAST TO SLOWLY SAG SWD AS MODEST BOUNDARY
   LAYER COOLING OCCURS /AS SUPPORTED BY 04Z RAP AND 00Z NAM FORECAST
   SOUNDINGS/. HOWEVER...A WARM NOSE CENTERED NEAR THE 800 MB LEVEL IS
   EXPECTED TO RESULT IN AN INITIALLY MIXED P-TYPES. AS THE LARGE-SCALE
   SYSTEM AND PRECEDING LOW-LEVEL JET SHIFT EWD...COOLING WITHIN THIS
   LAYER SHOULD EVENTUALLY LEAD TO A TRANSITION TO ALL SNOW ACROSS A
   CORRIDOR FROM THE NERN TX PANHANDLE INTO S-CNTRL KS...WITH RATES OF
   1-1.5 INCH PER HR POSSIBLE. FARTHER S...THE WARM LAYER CENTERED NEAR
   800 MB IS EXPECTED TO REMAIN MORE PRONOUNCED AND ABOVE
   FREEZING...WHILE NEAR- TO SUB-FREEZING SFC TEMPERATURES MAY FAVOR
   P-TYPES OF FREEZING RAIN AND/OR SLEET. CONVECTIVE ENHANCEMENT OF
   PRECIPITATION RATES IS ALSO POSSIBLE GIVEN THE PRESENCE OF STEEP
   MID-LEVEL LAPSE RATES AND ONGOING LIGHTNING S OF THE HIGHLIGHTED
   AREA.
   
   ..ROGERS.. 02/21/2013
   
   
   ATTN...WFO...ICT...OUN...DDC...AMA...
   
   LAT...LON   37169689 35789859 35170012 35130073 35510116 36020124
               36620096 37140032 37479959 37669894 37699771 37169689