MESOSCALE DISCUSSION 0116
   NWS STORM PREDICTION CENTER NORMAN OK
   1050 PM CST SUN FEB 20 2011
   
   AREAS AFFECTED...PORTIONS NRN/CENTRAL PA...NERN OH...WRN THROUGH
   SERN NY...NWRN NJ.
   
   CONCERNING...WINTER MIXED PRECIPITATION 
   
   VALID 210450Z - 210945Z
   
   CORRIDOR OF MDT-HEAVY SNOW FCST TO SPREAD FROM WRN NY AND NRN PA
   TOWARD MID-ATLANTIC COAST WHILE MAINTAINING POTENTIAL OVER
   N-CENTRAL/NWRN PA AND ADJACENT SECTIONS WRN NY THROUGH 10Z.  1-2
   INCH/HOUR RATES ARE POSSIBLE.  SRN PORTIONS DISCUSSION AREA...FROM
   NERN OH ESEWD ACROSS CENTRAL PA...LIKEWISE WILL SEE EXISTING
   PRECIP...IN THIS CASE FREEZING RAIN...SPREAD EWD...WITH SNOW
   TRANSITION TO FREEZING RAIN POSSIBLE OVER PORTIONS CENTRAL PA. 
   .05-.1 INCH FREEZING RAIN RATES MAY OCCUR IN EMBEDDED SHOWERS.
   
   ERN PORTION OF PRECIP PLUME -- SUPPORTED BY ELEVATED/LOW-LEVEL WAA
   AND RELATED UVV INTO DENDTRITIC GROWTH LAYERS -- WILL EXPAND EWD
   ACROSS DISCUSSION AREA.  AS THIS OCCURS...PRECIP INTO RELATIVELY DRY
   LOW-LEVEL AIR MASS NOW OVER NERN PA/SERN NY/NRN NJ WILL
   PROGRESSIVELY MOISTEN ANTECEDENT AIR MASS AND CONTRIBUTE TO COOLING
   VIA WET-BULB EFFECTS...AS ALREADY NOTED OVER CENTRAL PA AND AS FAR E
   AS AVP.  CONTINUED MOISTURE TRANSPORT INTO THIS REGIME OF BROADLY
   BANDED ISENTROPIC/FRONTOGENETIC ASCENT WILL SUPPORT INCREASING
   POTENTIAL FOR EMBEDDED HEAVY SNOW TO REACH GROUND.  MEANWHILE
   TRANSITION TO MIXTURE OF SNOW AND FREEZING RAIN...THEN JUST FREEZING
   RAIN...WILL OCCUR IN PORTIONS CENTRAL-WRN PA AS CONTINUED LOW-LEVEL
   WAA DEEPENS SUPERFREEZING LAYER JUST ABOVE SFC.  ALTHOUGH
   SMALL-SCALE VARIATIONS ARE LIKELY...LITTLE NET MOTION IN SFC
   FREEZING LINE IS EXPECTED DURING NEXT FEW HOURS ACROSS NERN OH AND
   WRN/CENTRAL PA WHERE WET-BULBING ALREADY HAS TAKEN PLACE...HOWEVER
   FREEZING LINE SHOULD SHIFT SWD SLIGHTLY OVER DE VALLEY REGION AND
   NRN NJ.  AFTER ABOUT 09Z...LOW-MIDLEVEL ASCENT IS PROGGED TO WEAKEN
   ACROSS THIS REGION...THOUGH POCKETS OF INTERMITTENT HEAVY SNOW STILL
   MAY OCCUR...ALONG WITH FREEZING RAIN ON SRN LIMB OF PRECIP PLUME.
   
   ..EDWARDS.. 02/21/2011
   
   
   ATTN...WFO...OKX...ALY...PHI...BGM...BUF...CTP...PBZ...CLE...
   
   LAT...LON   43167905 43087766 42897612 42377466 41747376 41217399
               40957489 40747815 40157863 40887939 40858030 41218143
               41758127 42247977 42547914 42717905 42787881 42957893
               43017900 43167905