How does sea effect snow develop?

It’s something we experience every year – sea effect snow.

As we’re talking more and more about it in the forecast, some are curious just how these sea effect flurries and squalls develop in our region.

The processes for sea effect snow are virtually the same as lake effect snow.

The key is having an airmass that’s much colder than the water. As strong winds blow colder air over the ocean, heat and moisture rise and condense to form clouds. The clouds continue to develop and downwind can produce flurries or intense snow squalls over land.

These bands can sometimes persist for hours or days, which is why it’s not uncommon for these events to dump large amounts of snow.

For us, sea effect snow is often generated in west or northwest winds off the Northumberland Strait and the Gulf of St. Lawrence, having the greatest impact on Cape Breton, the north shore of Nova Scotia, the west coast of Newfoundland and Prince Edward Island.

However, sea effect flurries and snow squalls can also develop off the Atlantic along west-facing coastlines in Newfoundland and off the Bay of Fundy in Nova Scotia, which locals call bay flurries.

A temperature difference of 13 C between the water and 5,000 feet above the surface often leads to the most significant events, with the distance the wind travels before reaching land, known as fetch, also a factor.

Remember that sea effect flurries and snow squalls are often incredibly localized – it can be sunny in one spot with blizzard conditions 10 minutes up the road, making them tricky to forecast.

But until the ocean is near freezing or sea ice forms, there will be more snow squalls to forecast in the coming weeks.