Here's What Could Change With Sunday's Nor'easter

As with any storm, particularly in the winter, details become more clear as we approach the actual event.

The two things we are most confident in right now:

1. Ski Country

Pretty much any way you slice it, Northern New England does great with this storm. Most spots see a foot or more of snow.

2. Wintry Mix South

We have high confidence that Southern New England will flip from snow Saturday night and early Sunday, to a wintry mix of rain, snow, sleet and potentially freezing rain during the day Sunday.

What we don’t yet know: just how much, or just where, mixing occurs.

Extreme Weather Photos: Storm Causes California Mudslides

Justin Sullivan/Getty Images

With that in mind, let’s dive into some of the factors that we are still sorting out, and will impact the final forecast.

1. Storm Track

It’s a simplified way of looking at it, but the final storm track really is key to what happens on Sunday.

Chanel Visionary Karl Lagerfeld Dies at 85

If the storm passes south of New England, more cold air will remain locked across the area. This would allow more snow, including around Boston.

By contrast, a storm that comes farther north, or through New England, would draw in slightly warmer air that would result in lower totals in Southern New England than we currently anticipate.

2. Sleet vs. Freezing Rain

Top News Photos: Winter Storm Blankets East Coast

Chip Somodevilla/Getty Images

This, arguably, is one of the biggest questions to figure out. Who in Southern New England sees snow versus sleet versus freezing rain when we do flip to the "wintry mix."

Sleet, the small balls of ice, accumulates much more slowly than snow. And freezing rain doesn’t accumulate at all—it just coats everything in ice. So, nailing down what falls in any given spot is tremendously important.

If cold air remains locked at the surface, but a lot of warm air rushes in at higher levels of the atmosphere, we’ll see more freezing rain. This would cut down on the expected snow, but it would make travel even worse.

Father, Grandfather Among 5 Victims of Illinois Shooting

If the cold air at the surface is a little more intense, and less warm air surges in aloft, we may end up seeing a good deal of sleet around Greater Boston. That would also cut down on totals to some extent and be a little less menacing than freezing rain on the roads.

The extent of the warming aloft comes back to the first point—the storm track. The farther north the storm comes, the more warm air comes along with it.

As I said before though—we are confident that we go over to a wintry mix, we just have to nail down what type of mix it is, and how far north it goes.

Aurora Ill. Shooting: Victims Identified

All of these questions will become better answered as we get closer to Sunday.

---

Get the latest from NBC Boston anywhere, anytime:

Download our FREE app for iPhone, iPad and Android. You can also follow us on Facebook, Twitter and Instagram, and sign up for our e-mail newsletters.