ZCZC SPCSWOMCD ALL
ACUS11 KWNS 021555 
SPC MCD 021555 
NYZ000-022200-

MESOSCALE DISCUSSION 0113
NWS STORM PREDICTION CENTER NORMAN OK
0955 AM CST SAT FEB 02 2013

AREAS AFFECTED...JEFFERSON COUNTY NY INCLUDING THE WATERTOWN AREA

CONCERNING...HEAVY SNOW 

VALID 021555Z - 022200Z

SUMMARY...SNOW RATES OF 2 IN/HR ARE ANTICIPATED IN A LAKE EFFECT
SNOW BAND OVER JEFFERSON COUNTY NY THROUGH THE AFTERNOON...AFFECTING
THE WATERTOWN AREA.

DISCUSSION...BUF/TYX 0.5-DEGREE REFLECTIVITY DATA DEPICT A SHALLOW
REFLECTIVITY BAND BECOMING BETTER DEFINED OVER LAKE
ONTARIO...ORIENTED WSW-ENE. THIS BAND REPRESENTS A WAVY LAKE EFFECT
HEAVY SNOW BAND THAT EXTENDS DOWNWIND OF THE LAKESHORE INTO
JEFFERSON COUNTY NY...AND RECENT WATERTOWN OBS INDICATE MODERATE TO
HEAVY SNOW ONGOING. MESOSCALE ASCENT SUPPORTING THIS BAND EMANATES
FROM /1/ THE RELATIVELY LONG OVER-LAKE FETCH LENGTH CONTRIBUTING TO
MODESTLY DEEP CONVECTIVE BOUNDARY LAYERS -- REACHING 7-9 KFT PER
FORECAST SOUNDINGS -- AND /2/ WARM ADVECTION IN ADVANCE OF A
MID-LEVEL SHORTWAVE TROUGH MANIFESTED IN A WEAKLY VERTICALLY VEERING
WIND PROFILE WITHIN THE LOWEST 1.5 KM AGL PER BUF VWP. THE
ISALLOBARIC RESPONSE TO PRESSURE FALLS DRIVEN BY THE WARM ADVECTION
WILL YIELD A TENDENCY FOR THE SNOW BAND TO GRADUALLY SHIFT NWD
TOWARD THE ST. LAWRENCE RIVER THROUGH MID-AFTERNOON.
THEREAFTER...SLIGHT LOW-LEVEL VEERING SHOULD PROMOTE A SWD
PROGRESSION OF THE BAND BY LATE THIS AFTERNOON. THESE
CHARACTERISTICS ARE ILLUSTRATED BY THE CONSENSUS AMONGST
HIGH-RESOLUTION WRF GUIDANCE...WHICH SUGGESTS THAT 2-IN/HR SNOW
RATES WILL BE LIKELY...MAINLY IMPACTING JEFFERSON COUNTY.

..COHEN/CARBIN.. 02/02/2013

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

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

LAT...LON   44097630 44187614 44177592 44077577 43897582 43767593
            43737615 43827631 44097630 

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