PENNSYLVANIA, USA — As Snow Squall Awareness Week continues, the State College National Weather Service continues to educate Pennsylvanians about the dangers, especially when driving on highways.
“We want to keep everyone safe this winter. So, when I say there is no safe place on a highway during a snow squall, guard your safety this winter and heed the warnings,” says Greg DeVoir, lead meteorologist at the State College National Weather Service.
When describing snow squalls, DeVoir uses an analogy to summertime thunderstorms, because of the release of instability.
“Snow squalls have the mechanism of instability involved in wintertime and anytime you have that you have a source of lift and intense precipitation falling out,” says DeVoir.
Triggered by an arctic front, or a very cold day with just the right ingredients i.e. showers and peeks of sunshine. The result is a quick burst of snow that leads to “white out conditions” or visibility reduced to less than a quarter of a mile.
"Picture that you’re on a high-speed highway and someone throws a blanket [at your windshield]. You can’t see out of your windows, you don’t know where the sides of the roads are, and you don’t know who’s in front or behind you or if they can stop with a flash freeze with a fully loaded tracker trailer behind you,” says DeVoir.
On top of low visibility, flash freeze is a major factor to watch for, and is what creates extremely slick roadway conditions. An example of this was seen during the pile-up in March of 2022 on Interstate 81 during that snow squall scenario.
“When you have road surface temperatures well above freezing when a squall arrives, the air temperatures could be the mid-20s but with road surface temperatures in the 40s or 50s the falling snow will melt and will freeze as the surface temperature cools to the air temperature,” says DeVoir.
Heading into this winter season, listen to local forecasters and have a plan if a snow squall warning is issued.
“If you hear a forecaster mention snow squall possible this afternoon, if you have highway travel planned, have an alternate route in mind, realize that there could be a warning issued while you’re traveling and you want to have a way to react to that in a non-panic way,” says DeVoir.