How lake breezes and lake shadows impact our weather

BUFFALO, N.Y. (WIVB) — During the spring, summer, and occasionally during the fall, we can get boundaries known as a “lake breeze” off Lake Ontario and Lake Erie. These boundaries can impact our weather — and one did just that this week.

A lake breeze is caused by the temperature difference between the lake water temperature and the land temperature. On land, we have warmer air and higher temperatures compared to the cooler lake water. In the warmer months, it takes the lake water longer to warm up. When we get a wind direction that allows for cooler air over the lake to move over land, it can result in what is known as a lake breeze.

In the yellow circle, you can see a faint line moving south from Lake Ontario, this is the lake breeze. This radar loop also showcases the convection being initiated off the lake breeze.

An example of this was observed on May 14, when we had a southeast wind ushering warmer air into the region and then a northeast wind off Lake Ontario. On land, temperatures for many reached into the 70s, while the water temperature for Lake Ontario was at 48 degrees. What this does is lead to that warm, less-dense air to rise as that cooler air moves in. As a result of this vertical motion, it can lead to convective processes in the form of cloud cover, showers, and even thunderstorms. This effect can be seen in Tuesday night’s radar.

Showers and thunderstorms developed in Genesee County as a result of the lake breeze.

A concern with lake breezes can be the potential for continuous shower and thunderstorm development over the same area, leading to heavy rain and flooding concerns. This was thankfully not the case Tuesday.

The cool stable air behind the lake breeze is the lake shadow from Lake Ontario which caused the showers and thunderstorms to weaken.

Aside from producing this boundary, cooler air is more stable. At times, you may notice the lack of cloud cover over Lake Erie or Lake Ontario. Even when we track severe weather, occasionally it will weaken over the lakes due to this cooler stable air. When it moves over land, we can get what is known as a lake shadow. We also had an example of this on May 14.

The cooler air not only helped produce a lake breeze, but behind the lake breeze was the cooler, stable air. Once the showers and thunderstorms moved past the lake breeze, they fell apart due to the cooler stable air not being able to support convective processes. When we say stable air, it inhibits the rising motion.

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