“We can measure that distance of each individual photon traveling inside the snow,” says Hu, a researcher at NASA’s Langley Research Center.Just as an ant wanders around its underground colony, a photon shot from a space laser takes a random route through the snow.

And while extreme events will continue to happen with greater frequency, what will also start to become common are “episodic low- to no-snow” events, when at least half of a mountain basin experiences low snow or none for five consecutive years.

Fueled by rapidly melting snowpack and a forecast of more rainstorms in the next few weeks, federal officials warn that 200 million people in 25 states face a risk through May. Floodwaters coursing through Nebraska have already forced tens of thousands of people to flee and have caused $1.3 billion in damage.

“For the future, that percentage will keep increasing,” says Zeng, who presented his findings at the annual meeting of the American Geophysical Union in Washington.LEARN MOREThe WIRED Guide to Climate ChangeAt the same time, the length of the snow season shrank by 34 days for the snowiest regions.