Buffalo, N.Y.’s “insane” lake effect snow storm was remarkable, and not only for the tremendous amount of snow that fell in 24 hours. The incredible symmetry and sharp boundaries of the event, and the stubborn persistence of the factors contributing to its severity have turned this week’s lake effect snow storm into one for the ages.

Lake effect snow occurs when cold air moves over warmer water, most commonly during cold snaps in early winter. The transfer of heat and moisture from the water to the air creates a shallow layer of convective instability — a meteorological way to say “this air is going to rise fast.” As the moisture rises and condenses it soon begins to fall in the form of snow.

The biggest lake effect snow events will occur when the winds are blowing parallel to the length of the lake. In this case, a wind out of the southwest will have plenty of time to pick up moisture from the warm waters of Lake Erie, before dumping it in the form of snow over western New York. On Tuesday, the surface water temperature of Lake Erie was a steamy 54 degrees Fahrenheit — a full 40 degrees warmer than the surrounding land temperatures.


(NWS)

The net result was a shallow, unstable air mass lying along on what effectively is a coastal front – not dissimilar, except for the much deeper vertical extent, from cold season coastal fronts along the southeast Atlantic shoreline.

Strong lake effect snow bands can develop parallel to the lake when the temperature difference between lake and air is very high. As air converges on the area of highest warmth, it rises and forms the single, intense snow band. On Tuesday, the upper level winds helped to steer the snow in a beeline toward the south Buffalo suburbs. The bands are a relatively narrow few miles in width, so it’s not unusual for one neighborhood to get clobbered while a nearby might get only an inch or two.


Surface winds over New York on Tuesday. (College of DuPage)

This week’s winds were alarmingly favorable for an intense snow band to set up along Lake Erie. The southwest wind trajectory was nearly parallel to the orientation of the lake, thereby increasing the length of time that low-level cold air has to pick up heat and moisture.

As the band of snow begins to form, an interesting thing happens. Air rises in the snowy regions and then sinks on either side, which creates an often cloudless, high pressure zone, and amplifies the distinct transition between snow and no snow. This effect maximized along the northeast shoreline between Lackawanna and Buffalo where, not surprisingly, the multi-feet, record amounts of snow fell, while minimal —  if any — fell just a few miles away.