The first accumulating snow of the season?

AccuWeather

In today's Forecast Feed, AccuWeather's Bernie Rayno takes a look at an upcoming stretch of December-like weather for the central and eastern United States.

Transcript

00:00December like cold? Absolutely. Accumulating snow? Probably not. And you're watching the feed.

00:10Let's get right into the cold. Sometimes people say, I bury the lead. I'm not going to bury it

00:14here. Take a look at this. This is what we're looking at as we head in the next week. A huge

00:20dip in the jet stream. Look how far south this goes, right toward the Gulf Coast. Widespread

00:24cold Monday and Tuesday. Record lows are probably going to be challenged here across the southeast.

00:31I'll show you that here in a second. But overall, temperatures 10 to 15 degrees below historical

00:36average. There will be a threat for snow in this area. Accumulating snow over the weekend?

00:43I think snowflakes will be falling, but I'm certainly not convinced we're going to see a

00:48whole lot of snow with this. But big pattern change. Let me show you how much, how fundamentally

00:53this pattern changes as we head into next week. So here's the pattern right now. And this is what

01:00I call a zonal flow. It goes from west to east. We see a zonal flow. All the cold air, and here's

01:05where it is. It's locked up in Canada. I'll put a C there. Now, across the south, boys, it's just been

01:11warm and dry in this whole area. I'll talk about that. That's a W right now. But watch how this changes.

01:17Let's focus on that. So here we are this morning. Let me take you to Monday morning. Watch the big

01:23change. We start from there, and we look at that change. So from here to there. Look at that. And

01:31then by Tuesday morning, look at that dip in the jet stream right in here. So with this dip in the

01:38jet stream, follow the lines. Where is it coming from? Straight from Hudson Bay all the way down

01:43into the southeast. That's why the cold is going to be so widespread. I want to show you the coldest

01:50time frame with this. It's going to be Monday night, Tuesday morning. These are the projected

01:54low temperatures. I know this might be a little hard to see, but look at this. This line here

02:00is the freezing line. Look how far south it goes. It goes all the way down to Interstate 10.

02:0620s all the way down to I-20 are in here. Look at that cold Tuesday morning across the southeast. Now,

02:15in the Midwest, your coldest mornings are going to be Monday morning. This is Monday morning with the

02:20freezing line down to about I-40. But look at this. Widespread 20s and even some teens. So again,

02:25it's cold, cold, cold. Now, oftentimes when you're dealing with cold air masses, you also have to deal

02:32with the possibility of snow. Well, we are going to be looking at a storm that will be arriving

02:38as we head in the set over the weekend. And this is the storm that can produce at least some snow here

02:45as it pushes across the U.S. here as we get in. Here it is Saturday and then here it is Sunday. So a

02:52lot of areas are going to get some snowflakes. The question is, are there going to be any areas that

02:58get accumulating snow? And I think it's odds are against that. And what I want to do is I want to show

03:04you some of the modeling with this storm. And I want to show you the tools that I use to help make

03:11a forecast here. So let me show you just a simple surface map here. So what's going to happen is

03:15this is storm number one. This storm right here. This is tonight's storm. This is tonight. This is

03:23going to go across Ontario and Quebec. And what it does is by Friday evening, it brings a little

03:29injection of cold air here. You see this line here. We call this the 540 thickness line. It's

03:35an approximation. I won't get into what it is. But this is where the air is cold enough aloft for snow.

03:41So you can see how far north that is. By Saturday morning, watch that line come south right there.

03:48Now by Saturday morning, by Saturday morning, that line goes all the way down to about Interstate 80.

03:55So cold enough aloft for snow, it doesn't mean you're going to snow, but at least that it's cold

03:59enough for snow. And then what you do is you bring in storm number two. That's going to be over the

04:04weekend. Here it comes Saturday morning. Watch that come eastward. There it goes. You see it now. You

04:10see a lot of the green. The green is rain. The blue is projected snow. And that includes cities like

04:15Madison, Chicago, Detroit, and then in the southwest Ontario. You see that? That'll be Saturday,

04:22Saturday night. So what the model is suggesting is, is that the air is cold enough for snow.

04:28Now, the question is, is it going to stick? And I think in a lot of cases, the answer is no. So I

04:36want to show you some more things that I look at here. What you're looking at here is this is called

04:41the upward motion field, because if you think about it for precipitation, you need upward motion. Now,

04:46what I want to show you is this. This is another way to look at this. You see this yellow here. Here

04:51comes our storm. Here's the upward motion. This black line is where it's cold enough aloft for snow.

04:59And you can see how far south it is. So all of this area, it's cold enough aloft for snow. And if

05:05you follow this out, you can see the upward motion. Look at all that red Saturday night.

05:10And it is south, though, of where you see a lot of the colder air. You see, this is where it's cold

05:16enough to snow, right? But where's a lot of the upward motion south of this line across Indiana,

05:21Ohio? Now, there is a little bit in here in Michigan, right in here. You see that little

05:26bit of yellow and orange and green? This is where you have upward motion and where there's going to

05:30be precip. And this black line is showing you where it is cold enough for snow. But most of the

05:36strongest upward motion and therefore precipitation is south of this line. That's why it's telling us

05:42much of what falls here is going to be in the form of rain. Let's play this out. Here's where it gets

05:47a little interesting, right in here. Sunday to Monday. Sunday afternoon in the Sunday morning here.

05:54You see that? All of a sudden, Sunday morning, look what's going on. You've got this area. Here's where

06:00that line is where it's cold enough for snow aloft. You got this upward motion in here across the Detroit

06:06area. Now, the question is, is okay, aloft, it's cold enough to snow in that area.

06:12But is the surface cold enough? And I want to show you one more tool. This is called the

06:16wet bulb temperatures. This is where you take the combination of the temperature and the humidity.

06:23And if you're precipitation in a dry atmosphere, you can get the temperature down to freezing.

06:28What I see here, this is your 32 degree line. All your upward motion is in here. So that tells me

06:35moving forward, while there is going to be a little snow with this on Saturday, the big story

06:41is not that we're going to be looking at a lot of snow here. I don't think we're going to see many

06:45accumulating snow. But I'll tell you what, for much of the country, though, the cold is the big story.

06:51And that's the feed.

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