Lake-effect snow, decoded. When a lake makes its own snow.
Some snow falls from a storm. Lake-effect snow falls from a lake. When bitter cold air blows across a lake that is still relatively warm, the air picks up heat and moisture off the water, rises, cools, and dumps it all as snow on the downwind shore — in bands so narrow that one town can get two feet while the next town over sees sunshine. This page is the short version of how it works, why the bands are so intense, where it hits hardest, and what to do when one parks over your road.
WHAT IT ACTUALLY IS.
Cold air, warm water, and a snow machine in between.
Lake-effect snow starts when cold air moves over a lake that is warmer than the air above it. The air picks up heat and moisture off the water, rises, cools, and wrings that moisture out as snow on the downwind shore — the lake is doing the work a whole storm system usually does. It needs two things: a big temperature gap between the lake surface and the air above it (roughly 13°C / 23°F is the rule of thumb) and a long stretch of open water for the air to travel over, so the longer the fetch, the heavier the snow.
WHY THE BANDS ARE SO INTENSE.
A few miles wide, two feet deep, sunshine next door.
Lake-effect snow does not fall evenly — it falls in bands only a few miles wide, and inside a band the snow can come down at 2–3 inches an hour or more, with sudden whiteouts that drop visibility to near zero. The band barely moves while the wind holds steady, so the same few miles keep getting buried while a town five miles away stays dry — which is why the morning forecast can be right for the whole county and still wrong for your street. The heaviest bands can even produce thundersnow, lightning inside a snowstorm, and the season only ends when the lake itself freezes over and cuts off the moisture supply.
WHAT TO DO ABOUT IT.
Do not drive into a band. Wait it out.
The Great Lakes are the famous case — Buffalo, Syracuse, Cleveland, and Erie measure their winters in lake-effect feet — but the Great Salt Lake and Japan's Sea of Japan coast do the same thing, so if you live downwind of any big lake, know your lake-effect season, roughly November through February. If a band is sitting over your road, do not drive into it: the wall of white arrives in seconds and the cars ahead of you disappear, so wait it out, keep your lights on, and check Brzzy's forecast, live radar, and severe weather alerts before the sky makes the decision for you.
What is lake-effect snow?
Lake-effect snow is snow made by a lake: cold air blows across water that is warmer than the air, picks up heat and moisture, rises, cools, and dumps the moisture as snow on the downwind shore. It falls in narrow, intense bands instead of evenly over a whole region.
Why is lake-effect snow so intense in one place and absent next door?
The snow falls in bands only a few miles wide, and a band barely moves while the wind holds steady — so the same few miles keep getting buried at 2–3 inches an hour or more while a town five miles away stays dry. Inside a band, visibility can drop to near zero with almost no warning.
What conditions cause lake-effect snow?
It needs cold air over a relatively warm lake, with a temperature gap between the lake surface and the air above it of roughly 13°C / 23°F, and a long stretch of open water for the air to travel over. The longer the fetch — the distance the air travels over the water — the heavier the snow downwind.
Where does lake-effect snow happen?
The Great Lakes are the famous case — Buffalo, Syracuse, Cleveland, and Erie measure their winters in lake-effect feet — and the Great Salt Lake and Japan's Sea of Japan coast do the same thing. The season runs roughly November through February and ends when the lake freezes over and cuts off the moisture supply.
Does Brzzy tell me about lake-effect snow?
Brzzy shows your local forecast with hourly updates, live radar, severe weather alerts, GIF forecasts, and activity ratings that weigh the sky for your plans. Brzzy is free to download on iPhone.
More from Brzzy: Full weather glossary, Snow, Winter Storm
