[MCD] SWOMCD

Mon Dec 4 17:57:58 UTC 2006

ACUS11 KWNS 041759
SWOMCD
SPC MCD 041758 
NYZ000-050000-

MESOSCALE DISCUSSION 2269
NWS STORM PREDICTION CENTER NORMAN OK
1158 AM CST MON DEC 04 2006

AREAS AFFECTED...FAR SWRN NY...INCLUDING PORTIONS OF THE BUFFALO
METRO AREA

CONCERNING...HEAVY SNOW 

VALID 041758Z - 050000Z

A PRE-EXISTING LAKE EFFECT SNOW BAND IS EXPECTED TO BECOME ORIENTED
IN A MORE FAVORABLE ORIENTATION TO UP TO 2 IN/HR SNOWFALL RATES
BEGINNING AFTER 22Z OVER PORTIONS OF SWRN NY.

A VIGOROUS MID LEVEL VORT MAX AND UPPER LEVEL JET NOTED ON IR/WV
SATELLITE IMAGERY WERE MOVING ACROSS SRN WI DURING THE EARLY
AFTERNOON. STRONG AND DEEP VERTICAL MOTION AHEAD OF AND TO THE LEFT
OF THE UPPER LEVEL JET ENTRANCE REGION HAS SUPPORTED MODERATE TO HVY
SNOWFALL OVER SWRN LOWER MI. AS THIS SYSTEM MOVES EWD...LOW LEVEL
FLOW OVER LAKE ERIE WILL CONTINUE TO BACK AND STRENGTHEN. IN
RESPONSE...THE PRE-EXISTING SNOWBAND OVER LAKE ERIE WILL LIFT NWD.
RELATIVELY UNIDIRECTIONAL SHEAR SHOULD CONTINUE TO SUPPORT A SINGLE
BAND TYPE STRUCTURE. HOWEVER SPEED SHEAR MAY CREATE OCCASIONAL
BREAKS IN THIS BAND. AS THIS BAND BECOMES ORIENTED SW-NE...AN
INCREASING FETCH DOWN LAKE ERIE WILL OCCUR LATER THIS AFTERNOON.
INCREASING VERTICAL MOTION WILL SUPPORT MID LEVEL COOLING AND RISING
INVERSION HEIGHTS FROM THE PRESENT 7000 FT TO OVER 10000 FT...ALONG
WITH INCREASING LAKE INDUCED CAPE VALUES TO OVER 300 J/KG. THIS WILL
FAVOR HVY SNOWFALL DEVELOPING OVER SWRN NY SNOWBELT REGION AND
PORTIONS OF THE BUFFALO METRO AREA BY EARLY EVENING /AFTER 22Z/.
COMBINED WITH A FAVORABLE UPSLOPE COMPONENT INTO THE HIGHER
TERRAIN...SNOWFALL RATES UP TO 2 IN/HR ARE POSSIBLE BY 00Z. THE
HEAVIEST SNOWFALL BAND IS EXPECTED TO EFFECT NRN
CHAUTAUQUA/CATTARAUGUS AND NRN/CENTRAL ERIE COUNTIES.

..CROSBIE.. 12/04/2006

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

...NOTICE...
SPC WINTER WEATHER MESOSCALE DISCUSSIONS WILL BE ISSUED ON A
SCHEDULED BASIS FROM DECEMBER 1 THROUGH FEBRUARY 28...FOUR
TIMES A DAY...AROUND 00 UTC...06 UTC...12 UTC...AND 18 UTC
FOR SIGNIFICANT SHORT RANGE WINTER WEATHER EVENTS.

ATTN...WFO...BUF...

42997850 42927902 42397972 42247963 42247871 42337841 