What We Know About the Winter Storm About to Hit the US—and What We Don’t

On the past Over the weekend, when weather models first began predicting a winter storm that would sweep across much of the country, Shawn Sublette, a meteorologist who lives in Virginia, began telling people in his area to prepare for snowfall. “At that time, a lot of data was starting to point to a major snowstorm in the mid-Atlantic and Northeast, with a significant amount of ice heading south into the Tennessee Valley in the Carolinas,” Sublette says.

Then Split woke up Wednesday morning. “I look back at the data and say, ‘Wow,’” he says. The models were now structuring the storm much differently.

“Some of the data is showing significant amounts of ice loss in my area of ​​central Virginia,” he says. “That doesn’t mean I’m going to buy it yet. But there’s a whole lot of data that suggests heavy freezing rain, which is the kind of precipitation that’s liquid until it touches something and then freezes. That’s the thing that weighs down power lines. That’s the thing that weighs down trees and puts them on top of power lines.”

Meteorologists who spoke to WIRED say it’s still too early to say how this weekend’s storm will affect different areas of the country. But they say people in many states should start thinking ahead to the weekend and next week, and monitor more up-to-date forecasts from reliable local sources over the next few days.

On Wednesday morning, the National Weather Service issued a series of possible forecasts — what it called “key messages” — about the coming storm, forecasting heavy snow to fall Friday from the Rocky Mountain and Plains regions and move to the East Coast on Sunday. Freezing rain and freezing rain are expected to hit states south of the snow zone. Maps provided by the NWS show the storm struck nearly 30 states, from as far west as New Mexico and Texas, all the way to Maine and as far south as Georgia.

There is still a lot of uncertainty about how the storm will form and how it will affect specific areas. “We know that this storm system is completely saturated with water,” says Matthew Capucci, an atmospheric scientist and meteorologist who contributes to the Washington Post’s Capital Weather Gang. Capucci says the system collected a lot of moisture from the Gulf of Mexico, ensuring some form of precipitation across much of the southern and eastern United States. But there is still uncertainty about how other atmospheric elements shaped the storm. This includes a vortex of cold, low-pressure air in the upper levels of the atmosphere (called, in meteorological parlance, an upper-level low) that forms over the Pacific Ocean, the formation of which will help determine how and where precipitation falls.

“A wide area of ​​the southern and eastern United States will see more than two inches of water,” Capucci says. “Whether that comes in the form of rain, snow, sleet, sleet, or a combination of those, it’s still the wild card.”

The National Weather Service’s announcements are not winter weather warnings, but rather “messages,” Sublette says. The forecast will become more specific as the storm continues to develop. But there is enough data available to start preparing for the worst-case scenarios. Many of the areas a storm could hit are historically unprepared for severe winter conditions: A 2014 ice storm that swept through parts of Georgia and South Carolina left some areas without power for days. This storm will hit just a few weeks short of the fifth anniversary of a winter storm in Texas that caused two weeks of power outages and ultimately killed nearly 250 people.