(Illustration by Lisa Pringle)
This week’s question comes from Morning Brief reader Gabrielle, who asks, “Why is weather in Michigan always so unpredictable and changing all the time?”
Meteorologist Rob Shackelford: I would agree that Michigan’s weather can be surprising!
First off, when we’re talking about living near the Great Lakes, we always have to talk about lake-effect snow. The Great Lakes are the source of the warmth and then the continental air mass from Canada is the source of the cold. Those two temperatures clashing together are what get you the crazy lake-effect snow bands that produce sudden snowfalls.
Continental air masses are batches of air that stew and grow over large landmasses like North America. They become more severe the longer they sit before getting dislodged. During the winter months, the most common continental air masses that affect the US are polar or arctic in nature, which develop either in far east Russia or in Canada before being swept into the Lower 48 by strong northwest winds.
Let’s take Detroit. They’ll have a high of 40 and this cold front comes through. Their temperatures suddenly drop to a high below freezing with winds of 30 miles an hour bringing down the wind chill.
In places with less continental influence, you see less dynamic weather. Take Arizona, for example, you see certain times of year with very consistent temperatures. They don’t have as dynamic of weather, in my opinion, because you just don’t have as much air coming in and, if it does, it’s coming all the way from the West Coast.
It just doesn’t rain a lot there. If you look at the average precipitation in a year, it’s like 2 inches, which is crazy. Like, I can’t even imagine, like Atlanta gets that in like a day.
In Michigan, you can have a warm continental air mass forming over the Central Plains and it kind of spreads east. We’ve been seeing that a lot this year. A lot of the warmth always starts kind of just on the eastern side of the Rockies and the Central Plains, and it just kind of shifts over.
When a cold front comes through, boom, it’s like it never even happened.
Climate change may play a role here as well.
In the past, most of the Great Lakes would freeze over, and when that happens, you actually don’t have these crazy bands of lake-effect snow. That’s because you need the warm water of the lake to meet the cold front to create lake-effect conditions.
When the lake doesn’t ever fully freeze, you keep getting hammered.
It might sound counterintuitive, but a warmer lake temperature in that situation can lead to more dramatic, sudden snow.
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