What is a snow squall?

Today, a narrow band of snow swept through the Twin Cities. At one point, the wind and heavy downburst of snow brought I-94 northwest of Minneapolis to a close thanks to a multi-vehicle accident. The Weather Service then issued a snow squall warning, but what is a snow squall, exactly?

In laymen’s terms, I would describe it as something similar to a severe thunderstorm, where the precipitation isn’t necessarily the most noticeable feature to the storm. In the northwest Twin Cities metro, for example, there were 40-50mph winds associated with the quick burst of snow. Buffalo, Minnesota reported 2.5 inches of snow in 90 minutes.

That’s another thing about a snow squall. The “squall” is important, because it is akin to a squall line, as with thunderstorms. There is a leading edge, and a well defined end, particularly as the storm is at it’s strongest. Instead of a bloated mass of snow showers you get with a typical winter storm, it’s a quick, intense line.

The primary impetus for the National Weather Service issuing a snow squall warning is the reduction in visibility, such as was the case in the accident seen above. The strong winds and heavy snow lead to white out conditions, in which visibility is at or near zero. They are targeted like a thunderstorm or tornado warning, to a very specific part of the storm, even if the entire line stretches for a longer distance.

This was Minnesota’s first ever issuance of a snow squall warning. They more frequently appear east of the Great Lakes, and are quite the curiousity in Minnesota.

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