Duluth gets its first snow squall warning — but what is a snow squall?

DULUTH – Phones buzzed across Duluth on Thursday morning as the National Weather Service's (NWS) local office issued its first-ever snow squall warning.

What is a snow squall, you ask?

According to the weather service, it's an "intense burst of snow and wind" that can make for bad road conditions. A warning typically lasts 30 minutes to an hour and is issued for a relatively small area, similar to a tornado or thunderstorm warning.

Parts of the Twin Cities metro area also saw a similar quick burst of snow and low visibility Thursday morning, though no accompanying squall warning.

"It is going to be a pretty rare thing for us," said Joe Moore, warning coordination meteorologist for the NWS in Duluth. "I would be shocked if we issued more than one to three a year across northeast Minnesota and northwest Wisconsin."

That's mainly because it's often too cold for snow squalls in the region. They're much more common in New England states.

This winter season is the first time all National Weather Services across the country have the ability to issue snow squall warnings. The Duluth office is one of the first in the Midwest to deploy the tool.

For meteorologists to make the call, it usually means they expect subfreezing road temperatures and visibility of a quarter mile or less. "It's going to coat the roads and make conditions really dangerous really quickly," Moore said.

Meteorologists can predict conditions in which snow squalls might happen, he added, often before or after a strong cold front.

Duluth's squall Thursday, which brought 1.4 inches of snow in a 30-minute period, happened because the temperature was changing at a faster rate higher up in the atmosphere — ripe conditions for heavy precipitation and big snowflakes.

Around the metro, "It was interesting here for about an hour," said Caleb Grunzke, a meteorologist with the Chanhassen office of the National Weather Service. "The more significant snow was in the Duluth area, though there were some intense snow showers that went through parts of the metro here."

The Duluth-area warning was in effect from about 7:40 a.m. until 8:30 a.m. Thursday and encompassed Interstate-35 down to Cloquet. Just as quickly as the flurry came, it disappeared, leaving behind a light layer of the white stuff.

"Most snow squalls are going to be an isolated incident," said Moore, who added that they also move like storms. A warning was issued for Superior and other parts of Wisconsin's South Shore later Thursday morning.

The weather service sends out push-alert notifications to smartphones for squalls (something they only do for tornadoes and some flash flooding) because of the "urgent, life-threatening" nature of the storm, Moore said.

"We want to alert people, so if they're heading out the door to go shopping or start their morning commute, they know this is a big deal," he said. "This isn't your average snow shower."

Katie Galioto • 612-673-4478