Lake effect snows developed off Lakes Erie and Ontario in a well-aligned, cold, unstable west to southwest flow.  Strong winds not along allowed the snow bands to extend well inland, but produced significantly reduced visibilities in blowing and drifting snow. The Lake Erie snows produced significant accumulations well into the Rochester metro area. Off Lake Erie, the event began in a southwest across northern Erie and southern Niagara counties, and then settled south into southern Erie and Wyoming counties by mid morning Thursday (10th) after dropping 2 to 4 inches. A short wave then approached and lifted the band northward for several hours during the day across the metro Buffalo area and across Genesee and Monroe counties, then settled slowly south and stalled out for many hours during the evening 10th with very intense snowfall rates across the Buffalo south towns and Wyoming county. This band also dropped down across the lakeshore areas of Chautauqua county with intense rates with major implications on the NYS Thruway. The NYS thruway was closed between Dunkirk and the PA line with hundreds of motorists stranded. The activity dropped further south and set up across the southern tier counties for much of Friday (11th) before drier air advected in during the evening. The activity weakened and ended by midnight. Specific snowfall amounts included: Springville 27 inches; Perrysburg 24 inches; Colden and Arcade 23 inches; Warsaw 22 inches; East Aurora and Batavia 17 inches; West Seneca 13 inches; and Buffalo and Rochester 3 to 9 inches (from north to south).
Off Lake Ontario, a similar scenario ensued, several hours later. The band initially set up in the Watertown area Thursday morning and slowly settled south later Thursday into early Friday (11th) with intense rates across southern Jefferson and central Lewis counties. The band then settled further into southern Lewis and Oswego counties later Friday as winds veered a bit further before weakening Saturday morning as the drier air advected in. Specific snowfall amounts included: Highmarket 40 inches; Port Leyden 37 inches; Lowville 30 inches; Redfield 28 inches; Copenhagen 21 inches; Carthage 15 inches; and Watertown 11 inches.

Lake-Effect Snow in LEWIS, NEW YORK
From 10-DEC-09 04:00:00 to 11-DEC-09 20:00:00 (EST-5)
Property damage: 35.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Lake-Effect Snow in OSWEGO, NEW YORK
From 10-DEC-09 15:00:00 to 12-DEC-09 09:00:00 (EST-5)
Property damage: 25.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Lake-Effect Snow in MONROE, NEW YORK
From 10-DEC-09 03:00:00 to 10-DEC-09 21:00:00 (EST-5)
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Lake-Effect Snow in SOUTHERN ERIE, NEW YORK
From 10-DEC-09 03:00:00 to 11-DEC-09 20:00:00 (EST-5)
Property damage: 16.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Lake-Effect Snow in CHAUTAUQUA, NEW YORK
From 10-DEC-09 06:00:00 to 11-DEC-09 20:00:00 (EST-5)
Property damage: 22.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Lake-Effect Snow in CATTARAUGUS, NEW YORK
From 10-DEC-09 06:00:00 to 11-DEC-09 20:00:00 (EST-5)
Property damage: 28.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Lake-Effect Snow in NORTHERN ERIE, NEW YORK
From 10-DEC-09 00:00:00 to 11-DEC-09 20:00:00 (EST-5)
Property damage: 16.00K
Crop damage: 0.00K
Reported by: Public

Lake-Effect Snow in GENESEE, NEW YORK
From 10-DEC-09 00:00:00 to 11-DEC-09 20:00:00 (EST-5)
Property damage: 35.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Lake-Effect Snow in JEFFERSON, NEW YORK
From 10-DEC-09 04:00:00 to 12-DEC-09 09:00:00 (EST-5)
Property damage: 22.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Lake-Effect Snow in WYOMING, NEW YORK
From 10-DEC-09 03:00:00 to 11-DEC-09 20:00:00 (EST-5)
Property damage: 22.00K
Crop damage: 0.00K
Reported by: Broadcast Media