Parts of U.S. face intense winter weather, including so-called ‘atmospheric rivers’

Amna Nawaz:

A major storm system is hitting the U.S., dropping snow in the North and Upper Midwest. Heavy rain floods and tornadoes are threatening parts of the South. And Northern California is preparing for severe rains just days after another deadly storm flooded homes and triggered widespread power outages.

Stephanie Sy has our report.

Stephanie Sy:

The first major us winter storm of 2023 is ushering in the new year with snow and ice from the Midwest on up to New England.

Snowplows are working overtime in Sioux Falls, South Dakota, to keep the roads clear for emergency vehicles.

Clara, Sioux Falls Resident:

I had to park on the street last night because there's no parking at my apartment. And the plows went by and snowed me. So, I'm just trying to dig myself out with a car scraper.

Stephanie Sy:

The winter storm is also triggering a new wave of flight cancellations and delays, especially at Minneapolis-St. Paul International Airport, which got nearly a foot of snow.

Last night, a Delta jet slid off the icy taxiway there after landing, but no passengers were injured. The severe weather also spawned at least six tornadoes across Illinois Tuesday, mostly in the central part of the state. The National Weather Service said it was the largest number of rare January twisters Illinois had seen since 1989.

Meanwhile, a large swathe of the South is contending with the threat of both tornadoes and flooding. Downpours made for treacherous driving conditions in Moulton, Alabama. This drone footage captured floodwaters in Shepherdsville, Kentucky, Tuesday.

All that comes as Northern California is getting walloped by another powerful storm system days after a New Year's Eve deluge. San Francisco residents like Tink Troy filled sandbags to help protect their homes from fresh flooding.

Tink Troy, San Francisco Resident:

They're saying this one is going to be a lot worse, so I want to make sure that I'm prepared and not having to do this when it's pouring down rain, like I did on Saturday.

(LAUGHTER)

Stephanie Sy:

That weekend storm, a so-called atmospheric river, dumped 5.5 inches of rain on San Francisco.

Daniel Swain, a climate scientist at UCLA, explained what it is.

Daniel Swain, Climate Scientist, UCLA:

It's a bunch of water vapor moving fast above your head. And, really, it's a large volume of water. We're talking about many times the volume of the Mississippi River, for example, in the form of water vapor in the air.

Most of California's water systems can reasonably handle even very intense one-off storms, but when you start to see long sequences over days and weeks of repeated moderate-to-intense storms like this and atmospheric rivers bringing copious precipitation, the cumulative effect over days and weeks becomes much more difficult to manage.

Stephanie Sy:

Forecasters have warned this new storm could bring as much as four more inches of rain to Northern California, coupled with wind gusts of up to 50 miles per hour.

Swain said the frequency of major storms on the West Coast is just one of the many mixed effects of climate change.

Daniel Swain:

Our own research published earlier this year suggested that climate change has already doubled the risk of a prolonged and extremely severe storm sequence capable of producing severe flooding in California.

So there is evidence at this point that climate change is starting to exert an influence on extreme precipitation in this part of the world.

Stephanie Sy:

At the same time, climate change is worsening the Western drought. And, at least in the short term, this week's flooding rains will refill the desperately low major reservoirs in Northern California.

For the "PBS NewsHour," I'm Stephanie Sy.