MESOSCALE DISCUSSION 1954
   NWS STORM PREDICTION CENTER NORMAN OK
   0358 AM CDT TUE SEP 11 2007
   
   AREAS AFFECTED...PORTIONS WRN NY...SRN LAKE ONT...EXTREME NWRN PA
   NEAR LE...ERN PORTIONS LE.
   
   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 
   
   VALID 110858Z - 111130Z
   
   BKN LINE OF TSTMS -- MOVING EWD APPROXIMATELY 35 KT ACROSS CENTRAL
   LE AS OF 830Z -- SHOULD MOVE EWD OVER REMAINDER OF THAT LAKE AND
   ONSHORE BETWEEN ERI-BUF THROUGH 11Z.  ISOLATED STG GUSTS AND HAIL
   MAY OCCUR WITH ANY OF THIS ACTIVITY THAT PERSISTS...ESPECIALLY NEAR
   LAKE SHORE...HOWEVER THREAT APPEARS TOO MRGL/ISOLATED FOR WW.
   
   DEEP-LAYER SPEED SHEAR IS FAVORABLE BENEATH 50-60 KT 500 MB
   FLOW...AND SO IS LOW LEVEL CONVERGENCE ALONG FORCING BOUNDARY.  MAIN
   CONCERN WILL CONTINUE TO BE WEAK-MRGL INSTABILITY...ESPECIALLY AWAY
   FROM IMMEDIATE VICINITY OF LE.  OVER AND JUST DOWNWIND FROM
   LAKE...RELATIVELY WARM WATERS BOOST PRE-STORM SFC TEMPS INTO UPPER
   60S/LOW 70S...AMIDST UPPER 50S TO LOW 60S SFC DEW POINTS. 
   ACCORDINGLY MODIFIED RUC SOUNDINGS YIELD EFFECTIVE INFLOW LAYER
   ROOTED AT SFC...INDICATING SOME POTENTIAL FOR ANY STG-SVR GUSTS
   GENERATED ALOFT TO BE TRANSFERRED TO SFC IN DOWNDRAFTS. 
   HOWEVER...SUSTAINED INTENSITY OF UPDRAFTS AND DOWNDRAFTS IS IN
   QUESTION GIVEN VERY WEAK DEEP-LAYER LAPSE RATES THAT LIMIT
   MUCAPE/SBCAPE TO LESS THAN 500 J/KG.  ONGOING ACTIVITY INITIALLY
   DEVELOPED INVOF AND JUST E OF DTW ALONG SFC COLD FRONT...WHICH STILL
   IS EVIDENT AS REFLECTIVITY FINE LINE FROM N-CENTRAL OH NEWD ACROSS
   LE TO SERN ONT.  SOME BACKBUILDING IS POSSIBLE ALONG FRONT...HOWEVER
   RELATIVELY STABLE SFC AIR MASS S OF LAKE SHOULD PRECLUDE ORGANIZED
   SVR THREAT WITH ANY SUCH CONVECTION AS WELL.
   
   ..EDWARDS.. 09/11/2007
   
   
   ATTN...WFO...BUF...CTP...CLE...
   
   42148033 42797888 42907895 42987900 43057900 43097908
   43277905 43427861 43547802 43347770 43117766 42687793
   42067870 41977971