Lake Effect Summary: January 4-6, 2015

Maximum Snowfall: Lake Erie 8.0" (Brant); Lake Ontario 28.5" (Fulton)

Duration: 30 hours +/-

Flake Scale: 2 flakes**

Behind a powerful cold front, a brisk west to northwest flow of arctic air poured across the Great Lakes region on the evening of January 4^th.  This was the winter season’s first blast of arctic air as temperatures at 850 hPa (5k feet) plunged down to -20 to -24 Celsius across the eastern Great Lakes.

Lake effect parameters, and wind direction were nearly ideal for an intense early January lake effect snow band off Lake Ontario.  However, these same wind directions were not as favorable for a heavy Lake Erie snow band, as the westerly flow over the shorter fetch of the lake, with no upstream connection made for weaker bands of snow. The lake water temperatures were running a few degrees above normal at the start of this event, and both lakes were still virtually ice free. The lake waters contributed to lake induced equilibrium levels peaking at around 8 - 10k feet on Lake Erie, and 12 – 15k feet on Lake Ontario. Instability was further measured by lake induced cape values that rose to about 1000 J/kg over both lakes.

The classic west to northwest flow concentrated lake effect snows south of metro Buffalo, and south and east of Lake Ontario.

Sunday evening, January 4^th the lake effect snow bands were largely disorganized off Lake Erie with the westerly flow, though a little better organized east of Lake Ontario. Later in the evening, as wind shear diminished a band of heavy snow with an upstream connection to Georgian Bay was established over Lake Ontario. This intense band of snow arced over Lake Ontario and inland across Oswego and southern Lewis counties. Meanwhile minor bands of lake effect snow from Lake Erie fell across southwestern New York State through the night.

Behind an upper level shortwave the boundary layer winds veered slightly through the Monday morning hours. This brought a still intense band of lake effect snow off Lake Ontario southward, to now the shoreline of Cayuga and western Oswego Counties. Within the heart of this band, snowfall rates of at least 3 inches per hour fell. Lake Erie’s snow band still remained weak, and multi banded in structure through the Monday morning hours.

Monday afternoon winds again aligned to westerly, which organized a narrow but intense band of snow off Lake Erie over far southern Erie County. This narrow band of snow dropped up to an additional half foot of snow Monday night. Off Lake Ontario, while the lake effect snow band weakened some early Monday evening, and actually split into two separate bands for a time, it reorganized, and increased in intensity briefly late Monday evening upon the central Tug Hill region.

Backing wind directions and warming aloft Monday evening through Tuesday morning ahead of another shortwave trough of low pressure lifted the lake effect snow bands northward and weakened them through the Monday overnight hours. While the snow band off Lake Erie gave just a fresh coating to the Buffalo metro area, the Lake Ontario snow band continued to drop snow Tuesday morning with several inches falling over the Watertown area, slowing the morning rush hour.   

Here are some representative snow amounts from this event.