MESO: Mesoscale Discussion 2122

ACUS11 KWNS 252308
SWOMCD
SPC MCD 252307
NYZ000-260300-

MESOSCALE DISCUSSION 2122
NWS STORM PREDICTION CENTER NORMAN OK
0507 PM CST SUN NOV 25 2012

AREAS AFFECTED...PARTS OF WRN NY EAST OF LAKE ONTARIO

CONCERNING...HEAVY SNOW

VALID 252307Z - 260300Z

SUMMARY...A LAKE EFFECT SNOW BAND OFF OF LAKE ONTARIO WILL LIKELY
CONTAIN 1-2-IN/HR SNOWFALL RATES WHILE TRANSITIONING SLIGHTLY
NWD...THEN SWD...THROUGH TONIGHT.

DISCUSSION...ONE-HOUR PRECIP TOTALS IN ASSOCIATION WITH THE
WELL-DEFINED...PERSISTENT LAKE EFFECT SNOW BAND STRETCHING FROM
CNTRL/NRN OSWEGO COUNTY AND SRN JEFFERSON COUNTY EWD TO LEWIS AND
NRN ONEIDA COUNTIES ARE LOCALLY REACHING 0.25 IN/HR WITH THE
HEAVIEST SNOW BURSTS...PER MONTAGUE NY RADAR DATA. USING
SNOW-TO-LIQUID RATIOS OF 8:1 TO 10:1...SNOWFALL RATES OF 1 TO
LOCALLY 2 IN/HR ARE LIKELY OCCURRING IN ASSOCIATION WITH THE SNOW
BAND. THESE RATES ARE BEING AIDED BY THE LONG-FETCH-LENGTH...
OVER-WATER TRAJECTORIES PROMOTING SHALLOW CONVECTIVE
INSTABILITY...WITH NEARLY UNIDIRECTIONAL WSWLY/WLY FLOW THROUGH THE
CLOUD LAYER AS SAMPLED BY THE BUFFALO VWP. WHILE THE MAGNITUDE OF
THIS FLOW IS NOT PARTICULARLY STRONG -- GENERALLY 15-30 KT -- THE
UPSLOPE COMPONENT OF THE FLOW OVER THE UPWIND SIDE OF THE TUG HILL
PLATEAU WILL LIKELY MAINTAIN LOCALIZED 2-IN-HR SNOWFALL RATES INTO
THE EVENING AND OVERNIGHT HOURS.

THE SNOW BAND SHOULD REORIENT THROUGH THE OVERNIGHT HOURS. AFTER
00Z...A MODEST INCREASE IN PRESSURE FALLS TO THE NORTH SHOULD RESULT
IN BACKING OF THE LOW-LEVEL FLOW. THIS MAY INITIALLY DISRUPT THE
ONGOING EVOLUTION OF THE SNOW BAND...WITH THE BAND BECOMING
REDEFINED SLIGHTLY TO THE NORTH OF ITS ONGOING LOCATION EARLY THIS
EVENING. HOWEVER...THE HEAVIEST SNOW SHOULD REMAIN NEAR OR -- MORE
LIKELY -- SOUTH OF WATERTOWN. LATER IN THE NIGHT...LOW-LEVEL FLOW IS
FORECAST TO VEER TO MORE WLY...WITH THE SNOW BAND GRADUALLY SHIFTING
SWD.

..COHEN.. 11/25/2012

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

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

LAT...LON 43597620 43697622 43797627 43837630 43917620 43917585
43867550 43677539 43377541 43327571 43327607 43467631
43597620

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