This section of I-81 north where Monday’s pileup occurred is mostly a straight section of road, said Pennsylvania Department of Transportation District 5 press officer Ronald J. Young Jr.

“The average daily traffic volume for I-81 north at the crash location is 10,511 vehicles. The average daily traffic volume on I-81 south at the same location is 8,957 vehicles,” he said.

“Our data shows there were three crashes on I-81 north at this location between Jan. 1, 2016, and Dec. 31, 2020 (data from 2021 and 2022 are not yet available). There was one crash in 2017, one in 2018 and one in 2019. These crashes resulted in no fatalities, and the one crash in 2019 had a minor injury,” he said.

Weather’s role

The massive crash happened during a snow squall, a brief, furious, localized blizzard that can cut visibility to a few feet with little or no warning.

Emergency Response Specialist Peter Wichrowski is a meteorologist with the National Weather Service, Eastern Region Headquarters.

“These squalls can produce a quick accumulation of snow. They typically accompany a strong cold front (similar to showers and/or thunderstorms during the warmer season). In addition to moderate to heavy snowfall, the snow squalls can be accompanied by gusty winds, which will reduce visibility causing near whiteout conditions. Hazardous travel conditions are then expected as the snow squall moves through,” he said.

“Meteorologists know when the conditions are right for snow squall activity by analyzing data such as the presence of a front and ample instability.

“As an event nears, meteorologists will rely on radar data to track these squalls, and can issue a Snow Squall Warning (or a Special Weather Statement if the squall is less intense), with lead times from a few minutes to as much as an hour,” he said.

Wichrowski said the warnings “notify emergency personnel, our partners in the broadcast media, and go out on Emergency Alert Systems via the National Oceanic and Atmospheric Administration Weather Radio, which are special broadcast frequencies.”

He said that snow squall warnings, which the National Weather Service alerts specifically for, are relatively new, starting in 2018.

“In the past, many offices would issue Special Weather Statements to address these intense snow showers,” he said.

The National Weather Service advises drivers to follow this advice:

“If a snow squall warning is issued for your area, avoid or delay motor travel until the squall passes through your location. There truly is no safe place on the highway during a snow squall. However if you are already in transit and cannot exit the road in time, reduce your speed, turn on your headlights and hazard lights and allow plenty of distance between you and the car in front of you. It’s also best not to slam on your brakes. With slick/icy roads, this could contribute to the loss of vehicle control and also increase the risk of a chain-reaction crash.”