Chicago Weather

Weather 101: What Is a ‘Cutoff Low’?

Without the jet stream, storms can move very slowly

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The Chicago area is getting hit by a super-slow-moving storm that will bring a light snow chance for four straight days. The snow began Wednesday evening and won't completely leave until Saturday afternoon.

But "why" is this storm moving so slowly?

It's because this type of storm system is "cutoff" from the jet stream. The jet stream is a fast-moving river of air that carries storms across the country. If a storm is separate from the jet stream, it doesn't have that push needed to move quickly. These types of storms can spin over the same general area for days, keeping the rain and snow chance elevated a lot longer than a typical storm.

NBC 5 Storm Team Meteorologist Paul Deanno explains what a "cutoff low" is and how it's keeping the snow chance elevated for several days.

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