MESOSCALE DISCUSSION 1674
   NWS STORM PREDICTION CENTER NORMAN OK
   0437 PM CDT TUE AUG 07 2007
   
   AREAS AFFECTED...MI...IN....OH...PA
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 072137Z - 072230Z
   
   A WATCH IS POSSIBLE ACROSS PORTIONS OF THE UPPER MIDWEST/ERN GREAT
   LAKES FROM LOWER MI AND IND...EWD ACROSS NRN OH...AND PERHAPS INTO
   WRN PA. SLOW AIR MASS RECOVERY IN THE WAKE OF EARLIER MCS AND WARM
   AIR ALOFT MAY KEEP AREAL EXTENT OF THE SEVERE POTENTIAL LIMITED AND
   AREA WILL CONTINUE TO BE MONITORED.
   
   RECENT TSTM DEVELOPMENT ACROSS SWRN LOWER MI/NERN IND APPEARS TO BE
   OCCURRING ALONG WARM/STATIONARY FRONTAL ZONE SITUATED ACROSS THE
   REGION. WEAK BOUNDARY LAYER CONVERGENCE BUT STRONG MOISTURE FLUX
   ACROSS THIS BOUNDARY...COUPLED WITH STRONG HEATING...HAVE PROBABLY
   AIDED RECENT STORM INITIATION. LARGE SCALE FORCING FOR ASCENT ACROSS
   THE REGION IS FORECAST TO REMAIN WEAK/LIMITED IN THE WAKE OF SHORT
   WAVE/MCV NOW MOVING ACROSS NY/PA. HOWEVER..ANOTHER LOW AMPLITUDE MCV
   MAY BE SPREADING ACROSS LAKE MICHIGAN AT THIS TIME. WARM
   TEMPERATURES ALOFT HAVE BEEN SOMEWHAT OFFSET BY VERY MOIST BOUNDARY
   LAYER DEWPOINTS WELL INTO THE 70S F AND ARE CONTRIBUTING TO MLCAPE
   VALUES APPROACHING 2500 J/KG. AIR MASS FARTHER EAST...ACROSS OH INTO
   PA...HAS BEEN SLOW TO RECOVER AFTER PASSAGE OF EARLIER MCS.
   
   WHILE MARGINAL SEVERE HAIL MAY BE POSSIBLE...THE CHANCE FOR 
   DAMAGING TSTM WINDS MAY INCREASE OVER THE NEXT COUPLE OF HOURS. BAND
   OF MID LEVEL FLOW OF 40-50KT WILL SUPPORT BOTH FAST CELL MOTION AND
   SUFFICIENT SHEAR TO SUSTAIN STRONG UPDRAFTS. GIVEN CELL MOTION OVER
   30KT...AND ABUNDANT INSTABILITY...ONE OR TWO STORM CLUSTERS MAY
   SPREAD EAST ALONG THE FRONTAL ZONE AND POSE AND INCREASING THREAT OF
   DAMAGING WINDS. CURRENTLY...AREAL EXTENT OF THIS POTENTIAL APPEAR
   LIMITED BASED ON AIR MASS RECOVERY...TIME OF DAY...AND LATEST
   GUIDANCE. IF ACTIVITY CONTINUES TO INCREASE IN INTENSITY AND
   COVERAGE...A WATCH MAY BE NEEDED.
   
   ..CARBIN.. 08/07/2007
   
   
   ATTN...WFO...PBZ...CLE...ILN...DTX...IWX...GRR...
   
   42848425 42338180 41598013 40738132 40678327 41068573
   41828645 42888548