Lake Effect Summary: December 30 - January 2, 2015

Maximum Snowfall: Lake Erie 13.5" (Wyoming); Lake Ontario 24.2" (Scriba)

Duration: 60 hours +/-

Flake Scale: 3 flakes***

A strong and cold surface high pressure of arctic origins moved south into the Northern Plains on December 29^th and 30^th, pushing a very cold airmass into a large portion of the nation including the Great Lakes region.  The airmass was initially too dry and sheared to support any lake effect snow despite being cold.  This started to change during the late evening of December 30^th with the approach of an upper level disturbance moving through southeastern Canada.  This provided enough background moisture to allow lake effect snow to begin, and winds also became better aligned.  Conditions become more favorable for heavy lake effect snow on New Year’s Eve and New Year’s Day as somewhat deeper moisture and even colder air moved into the region and allowed lake induced instability to increase, especially across Lake Ontario. 

Off Lake Ontario…

This lake effect event had a very interesting beginning as a meso-low formed over Lake Ontario in response to increasing lake induced instability and a very weak background synoptic wind flow.  A meso-low is a small scale low pressure system, formed in this case by warmth released from Lake Ontario and land breezes converging from both shores of the lake.  Increasing westerly winds during the evening of December 30^th carried this meso-low into the eastern Lake Ontario region with a few hours of heavy snow.  Behind the meso-low a more traditional band of lake effect snow developed overnight across central and northern Oswego County extending into the southern portion of the Tug Hill Plateau.  Snowfall rates reached 2 to 4 inches per hour as the band intensified in response to deepening moisture and instability.  The band of heavy snow continued across Oswego County through the middle of the day on the 31^st before moving north toward Watertown in the afternoon.  As the band moved north it weakened somewhat as shear increased across Lake Ontario. 

The band remained across Jefferson and far northern Lewis County New Year’s Eve into New Year’s morning with subtle changes in wind direction forcing the band to meander several miles north and south at times.  The band occasionally split into two distinct bands of snow to the north and south of Watertown due to some shear, and also occasional upstream connections to bands from Lake Erie.  The band of snow became weak and disorganized for a few hours on the afternoon of New Year’s Day due to drier air and more shear over the lake.  The band of snow moved south on the night of January 1^st and intensified across the Tug Hill region overnight.  Snowfall rates reached 2 to 3 inches per hour by early morning on January 2nd as it moved further southward across Oswego County.  The band clipped portions of Northern Cayuga and northeast Wayne counties during the day on January 2^nd but high pressure building closer to the lake resulted in a rapid weakening trend as shear increased and moisture decreased.  The last vestiges of the lake effect snow dissipated on the evening of the 2^nd across Oswego County.

Snowfall amounts were moderately high in this event with around 2 feet across central and northern Oswego County, and 1 to 2 feet farther north across central and southern Jefferson County into far western and northern Lewis County.  The unique features of this event make it more memorable, with the meso-low to start and the split bands on New Year’s Eve.       

Off Lake Erie…

Multiple bands of light to moderate lake effect snow developed first on a westerly flow on the night of December 30^th across the western Southern Tier.  This remained weak through the night due to dry air and shear with just a few inches of accumulation.  The snow remained disorganized into the morning of the 31^st across the Southern Tier.  Lake effect snow then moved north towards Buffalo during the day as winds become more southwest over Lake Erie.  Conditions were never as favorable over Lake Erie with more shear, less moisture, and less instability; resulting in a much more disorganized band most of the time.  On New Year’s Eve shear resulted in the band being split in two over Buffalo most of the time, resulting in light and spotty accumulations.  Interestingly, the two bands of snow merged back together across Genesee County where much heavier accumulations occurred.  The band moved south into Southern Erie and Wyoming counties overnight.  Snow amounts remained light close to Lake Erie with greater amounts farther inland across far eastern Erie and Wyoming counties. 

On New Year’s Day lake effect snow shifted north through the Buffalo area as winds become more southwesterly again.  Increasing amounts of shear and decreasing instability kept this very light through the day with just occasional light snow showers across the Niagara Frontier.  A mid-level disturbance crossed western New York during the evening of January 1^st and provided some help to the lake effect snow in the form of deeper moisture and some added lift.  This allowed for a brief and modest uptick in snow, again mainly inland across Genesee and Wyoming counties.  By the morning of the 2^nd lake effect snow had pushed back into the western Southern Tier, where it remained a broad area of disorganized snow showers and only produced light accumulations.  The snow ended completely by the afternoon as instability became too weak to support any further lake effect.

The Lake Erie snow under-performed compared to Lake Ontario with lackluster snow totals.  The highest amounts were well inland across Wyoming and Genesee counties with 9 to 13 inches, while areas closer to the lake including the Buffalo metro area had far less.  Bands of lake effect snow moved into the Southern Tier several times during this event, but were weak each time with only a few inches of accumulation.  While weak, this event will be remembered for the unique placement of the heaviest totals well inland from the lake due to the band splitting around Buffalo.     

Here are some representative snow amounts from this event.