What to expect from the potentially devastating winter storm

Geoff Bennett:

A sprawling and potentially devastating winter storm is projected to slam a massive swathe of the country tomorrow and through the weekend from New Mexico all the way to Northern Maine.

Heavy snow, life-threatening cold and dangerous ice accumulation are all in the forecast. More than 130 million people are currently under winter storm alerts, and nearly every American east of the Rockies will be affected. That's according to the National Weather Service.

To help break down what we expect to see and how you can prepare, we're joined now by MyRadar senior meteorologist Matthew Cappucci.

Thanks for coming in.

Matthew Cappucci, Senior Meteorologist, MyRadar:

Yes, good to be here.

I have to say, the scale of this storm is matched only by its intensity. I mean, the fact that we have roughly 1,800 miles nonstop of winter storm alerts, watches, warnings from Arizona all the way to the East Coast shows just how big this storm is.

It's getting going right now off the U.S. West Coast. That's an upper-level pocket of cold air or low pressure and spin, this big swirly twirl on the water vapor satellite. It's kind of the impetus for the storm system. But you will notice it's still offshore. So we can't launch weather balloons into it.

And so actually last night the hurricane hunters, those folks who fly into hurricanes, flew into this storm to collect data to help us figure out what this thing's going to do. We pump that into models. And you can see just an absolute mess on the simulated radar, rain, snow, sleet, freezing rain, the worst of everything from New Mexico, Texas all the way to Southern New England.

Geoff Bennett:

What does the forecast say about snowfall? Where do we expect to see the most?

Matthew Cappucci:

So I think the snow jackpot should be in roughly a 50-to-100-mile-wide zone north of the rain/snow line. It starts near Oklahoma City, pushes northeast all the way towards D.C., Baltimore, Philly, New York City.

All those places have a roughly 50/50 shot of seeing a foot or more of snow, Tulsa probably 12 to 18 inches. Then Southern Missouri, the Bootheel, Western Kentucky along the Ohio River, that's where the worst will be. But in addition to that, on the southern side. It's not just the snow. It's the sleet and the freezing rain too.

Geoff Bennett:

And what about the life-threatening cold? There's also threats of ice accumulation.

Matthew Cappucci:

Yes, the ice accumulation is really what worries me the most, because for folks at home, ice happens when you have rain that essentially falls as a liquid and then turns into ice on the ground, given sub freezing surface temperatures.

In that freezing rain zone, temperatures might be in the mid-40s a mile above the ground. So liquid rain is going to fall, but the surface might be 25, 30 degrees. So all that liquid freezes on the ground.

Two main areas. I'm really watching for the worst ice accretion, I think Northwestern Mississippi, Northeast Louisiana, probably south of Memphis along Interstate 55, that's the zone I'm really watching for potentially significant ice accretion. We're talking like a half-inch to an inch in spots.

And it only takes about a -inch of ice to pull down the power lines, get power outages, the roads impassable probably from Friday night all the way through Monday morning. And then behind it, of course, the cold comes in.

The other zone I'm really watching, northeast of Atlanta into for example the Western Carolinas, Asheville, Greensboro, Spartanburg, Greenville. I'm really worried that cold air at the surface draining down the Appalachians will keep the surface subfreezing even when it's warmer upstairs, so again serious ice accretions possible northeast of Atlanta.

And I wouldn't even be surprised for some thunder sleet and thunder ice to mix in too, thunder...

Geoff Bennett:

Thunder ice.

Matthew Cappucci:

Thunder, lightning, freezing rain all at once.

Geoff Bennett:

All right, Matthew, so two questions. What are the dangers of this type of weather and what should people be doing to prepare?

Matthew Cappucci:

You know, I'm really concerned about both the snow and the ice, especially, because, snow, you can pre-treat. You can put stuff down in the roadways.

Ice comes down as a liquid and it washes away any pretreatment. So I think it's going to be like a skating rink for a lot of people until the middle of next week.

And the worst part, given these cold temperatures invading, there's nothing to really melt this until the end of next week. Look at temperatures early Monday morning. We're talking negative double digits over the Upper Midwest, the Northern Tier, excessive cold warnings in effect for a wide area from really Minnesota down to Oklahoma City, single digits, below zero, Little Rock, Oklahoma City, single digits above zero in Texas.

And given how much ice is coming down, I think a lot of folks will likely lose power too. So you have systematic -- the issues with vulnerability. You're going into a cold air outbreak with a lot of people who won't have power. I'm very worried about that.

So, given the forecast, I'd say bundle up. Make sure you have everything you need for about three to five days off the grid. Make sure you're taking care of elderly, vulnerable neighbors, loved ones, and ultimately having a plan to hunker down for days on end.

Geoff Bennett:

That is good advice.

Matthew Cappucci, our thanks to you, as always.

Matthew Cappucci:

Thank you.