What are snow squalls and why they’re more dangerous than blizzards

By Allison Chinchar, CNN Meteorologist

Driving in a snow storm is difficult. Add in blowing wind and poor visibility, and travel can become downright dangerous. And driving in a snow squall is next to impossible.

“There is no safe place on a highway during a snow squall,” the National Weather Service (NWS) warned.

A snow squall is an intense, but limited duration, period of moderate to heavy snowfall, accompanied by strong, gusty surface winds and possibly lightning. Snow accumulation may be significant. The phenomenon is not new, but the term and warnings associated with it only began in 2018.

Snow squalls are different from a typical snow storm mainly because they are much shorter-lived, but also because they often have something called a flash freeze. Rapidly falling temperatures along with the freshly fallen snow can quickly glaze highways.

“The flash freeze is what separates snow squalls from a run-of-the-mill snow shower, which happens all the time,” said John Banghoff, a meteorologist at the NWS in State College, Pennsylvania

“The flash freeze component essentially makes travel and controlling a vehicle next to impossible,” added Jonathan Guseman, Warning Coordination Meteorologist at the NWS office in State College.

Snow squalls versus blizzards

There are two main types of snow squalls: frontal and lake effect.

Frontal snow squalls occur ahead, along, or behind an arctic front. The front provides the moisture and wind variables needed, and a very intense squall line develops producing the narrow bands of heavy snowfall. Very similar to a line of severe storms with tornadoes or damaging winds that occur in warmer temperatures, snow squalls are narrow but very intense.

A snow squall generally lasts less than 30 minutes at any given geographic point along its path, however, the entire line stretched out from its forward movement can cover large distances.

“A snow squall often occurs along an arctic front and the plummeting temperatures behind the snow squall turn wet pavement into a sheet of ice, making snow squalls much more dangerous than snow ‘bursts’,” Guseman noted.

Lake effect snow squalls occur only near a large body of water. Lake effect snow occurs when cold air, often originating from Canada, moves across the warmer waters of the Great Lakes. The two types of events differ in duration. Lake effect snow squalls can extend long distances inland, and can persist for many hours. Snow accumulations can exceed 6 inches in a matter of hours.

Snow squalls, while they have similar characteristics, are not the same as blizzards.

A blizzard is defined as a storm with “sustained or frequent winds of 35 mph or higher with considerable falling and/or blowing snow, frequently reducing visibility to 1/4 of a mile or less.” The conditions must persist for a minimum of 3 hours.

Snow squalls also have the requisite frequent wind gusts of 35 mph or greater and visibilities 1/4 mile or less, but are shorter in duration, must contain the flash freeze hazard, and require heavy snowfall.

Snow squall warnings are focused on very distinct, localized areas (like tornado and severe thunderstorm warnings).

There is ‘no safe place’ on a road during a snow squall

The greatest threat from snow squalls is travel. Visibility declines rapidly during snow squalls making travel almost impossible.

Guseman and Banghoff emphasized planning ahead and knowing when snow squalls are possible are key to avoiding getting caught on the road.

However, if you do get caught in one, Guseman and Banghoff have some tips

• First, remain calm. Panicking will not help.

• Try to safely exit the highway at the next available opportunity

• Don’t make any quick or sudden movements (gradually reduce your speed and increase following distance)

• Make yourself as visible as you can by turning on your headlights and hazard lights

Unfortunately, there is a long history of deadly traffic accidents associated with snow squalls, especially due to the quick reductions in visibility and flash freeze.

This video shows exactly what can happen when visibility drops rapidly during a snow squall on the highway. Back in January 2015, whiteout conditions were blamed for shutting down Interstate 94 after nearly 200 vehicles were involved in a chain-reaction pileup.

Guseman and Banghoff emphasized “there is no safe place on a highway during a snow squall,” so it is best to avoid the situation at all by not getting in your vehicle and just staying where you are, at home, work, or school.

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