Happy #WeatherWednesday everyone! Now that we got our first taste of colder air across the Southern Plains, we switch from talking about hurricanes to talking about winter weather! Meteorological winter starts in under two months (December 1).
Lake effect snow is a term heard a lot in the Midwest and Northeast US. This phenomenon is common over the Great Lakes region in late October through late January, but in some cases can occur as late as March and early April. Lake effect snow requires several ingredients to come together. These conditions can last for a few hours or a few days.
L.E.S. in general is easy to forecast and almost a certainty to exist if you know what to look for in upcoming weather conditions. Relatively cold low level flow (below freezing) after cold front passages that encounter lengthy travel over unfrozen and warmer lake surfaces will modify due to thermal energy release from the water to the air. Once the flow reaches the lake shore after warming and gaining liquid water content, it encounters colder air. The onshore flow suddenly rises over the cold land air due to the air density differential. When it rises it gets colder and condenses and the surplus water content picked up over water precipitates downwind over land as snow.
Water has a high specific heat capacity, so a lake holds its heat many times longer than land does. This can allow for many long lives L.E.S. episodes in one season until the lake water is too cold or frozen to produce convection. If the lake surface is frozen during cross-lake flow, then thermal energy transfer into the environment is impeded, effectively killing the “lake effect snow machine.”
The fly in the forecasting ointment can be determining placement or lateral movement of the snow bands. This can make identifying which areas will have significant accumulation and which won’t fairly difficult. You could be seeing sunshine and clouds for a day with no snow while a community a mile away gets nonstop snowfall instead.
Southern Buffalo, NY had the most epic lake effect episode in 2014 from 11/17-11/20 where accumulations topped 7 feet. The “snow belt” is locally known as the lake effect prone area running from NE Ohio into SW New York. The combination of higher terrain just off the Lake Erie shore and the curvature of the coastline enhance the lift and onshore fetch needed for L.E.S.
In rarer cases some bigger lakes around the country (even in North Texas) can experience short-lived spells of lake effect snow.
There is also such things as lake effect rain and storms when the temperatures are above freezing downwind of a warmer lake.