SWOMCD
SPC MCD 110858
NYZ000-PAZ000-111130-
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
..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...BUF...CTP...CLE...
42148033 42797888 42907895 42987900 43057900 43097908
43277905 43427861 43547802 43347770 43117766 42687793
42067870 41977971
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