00:00Here on the forecast feed, all week long we've been looking at different aspects of the major
00:04winter storm that is going to bring tremendous impacts to the southern plains, the southeast,
00:09even parts of the Midwest, the Ohio Valley and the northeast. A huge portion of the nation
00:14affected in a severe way here this weekend, Friday night through Saturday, Sunday, and into Monday,
00:20initially in the southern plains, then into the northeast. A quick overview, I'm going to spend
00:24a little bit more time taking us through the vertical profile of the atmosphere. Again,
00:30we want to talk about the difference between sleet and freezing rain and a disparity here in some of
00:35the computer models. About a 10 to 20 degree difference Sunday afternoon in Atlanta. Might
00:42be dealing with 50 degrees in rain or could it be freezing rain and 30. We're going to show you a
00:48huge disagreement there in certain spots and other areas that we're very confident in big, big trouble
00:53regarding snow north. And look at this, you can see also moisture from the southwest feeding into
00:58this. We've got an arctic front shoving south, making its way all the way down to the gulf. We
01:02got moisture and warm air near the gulf. So for many reasons, among them also some jet stream energy,
01:09obviously a big factor in this. Let's go back upstairs here to 500 millibars. Just briefly,
01:14you can see a couple of the players on the field. We have an area of, well, different spokes of energy
01:20here in the upper, the northern branch of the jet stream. We've got that big zone of low pressure
01:24over parts of the southwest. There's your low. And we're going to be dealing with a kind of a
01:31consolidation here of all these factors as an arctic front pushes south, driving a lot of trouble here
01:37into the southern plains initially. And then by Sunday, all the way up into the northeast, Saturday
01:43and Sunday, we're going to be dealing with an expanding storm as the northern branch of the jet stream
01:48and the southern branch of the jet stream work together here. And we're dealing with these phasing
01:53into a big mess. Now, we talked about some things aloft over the past couple days, differences between
01:59the European and the GFS. I want to focus on the freezing rain. We're going to begin briefly with
02:04rain in Dallas. It might be 50 degrees or 45 degrees, probably in the 40s, around early afternoon. We'll be
02:11in the 40s in Dallas as rain begins. But then quickly, this arctic front shoves south, and we're going to see
02:16a changeover in the area of pink here. That's going to be freezing rain. Then in peach, that's that sleet,
02:23and then snow to the north. So this is Friday evening and into Friday night as this really pushes south.
02:28And then we deal with the widespread icy mess into Tennessee. The Carolinas is a classic cold air damming
02:35setup. Look at the isobars kicked sharply down on the east side of the mountains. That means with this area of high
02:41pressure to the north, we're dealing with that cold press. Cold air is dense. It hugs the ground
02:47and it gets stuck east of the mountains here. So that cool flow traps the cold air. So upstairs,
02:55you're going to have warmer air overrunning cold air east of the Appalachians. Classic setup for an ice
03:01storm here. Now, if the cold air is deep enough, you get sleet. If it's very shallow, these raindrops don't
03:07get a chance to freeze until they hit the ground. So let's go upstairs here. This is where we get
03:11into something that's a little more technical. And we're going to begin in Dallas. Let's take you to
03:15Dallas. So this is the vertical profile of the atmosphere. Here's the ground, all the way down
03:21here at the ground. And then at 300 millibars, this is where an airplane would fly. We're going to try to
03:25draw an airplane here. This would be a 747, a big, large airplane, 30,000 feet up into the atmosphere,
03:32several miles up. The red line is the temperature. The green line is the dew point. So when they are
03:38pancaked together, you're going to have nothing but clouds. It's saturated. And this is a sign that
03:43we're dealing with a saturated atmosphere. Initially, Friday afternoon, here's the tricky
03:48thing. This is why it's a little bit tricky to interpret. This is the freezing line. And it's
03:54diagonal. So it's a little bit tricky. This is something that freshmen in college wrestle with
04:00when they're learning the first stages of, you know, meteorology 101. If you're right of that
04:05freezing line, you're warmer than freezing. If you're left of it, you're colder than freezing. So
04:09way upstairs, 10,000, 12,000, 15,000 feet up, you got snowflakes falling, and they reach this warmer
04:15layer in Dallas, and it rains. Well, that's just the very beginning of the event. The Arctic front
04:19pushes south, and watch what happens. We're going to go from rain, suddenly, Friday evening, when Tony
04:26Lawback is giving us some live reports on the AccuWeather Network. Look at this. We get below
04:30freezing for a chunk. So these are raindrops that are falling, falling, falling, and then they begin
04:35to freeze, but they probably don't get a chance to freeze until they hit the ground, because that
04:39layer of colder than freezing air is very shallow, just a few hundred feet deep. And then it deepens.
04:46Watch this into Saturday. It gets deeper. So now we've got an issue with warmer than freezing,
04:51and then for the lowest, maybe 2,000 feet, colder than freezing. So now you got raindrops that get
04:57a chance to freeze, and they bounce as sleet pellets onto the ground. That'll be easier to
05:02deal with in the freezing rain. Still, it's not good. And then we have a lot of sleet, tons of
05:06sleet into Dallas. Let's go farther east, though. This is where it gets messy. I'm going to just take
05:11us into, this is Atlanta. This is Atlanta, the GFS and the European. This is that big disparity
05:15that I was looking at here. So initially, we're saturated, and we're probably dealing with
05:23freezing rain with this sounding here. Here's the freezing line. There's zero. And this is warmer
05:30than freezing, and then just a little bit near the ground, colder than freezing. So the raindrops
05:35fall into that, and I'm going to exaggerate, the knee-deep chill, and the raindrops freeze on any
05:40surface. That's freezing rain. And there's pretty good agreement, generally, generally pretty good
05:45agreement here, approximately between the GFS and the European. Let's go to 1 p.m. Sunday.
05:50Look at this. Freezing rain in the GFS. Still warmer than freezing for a big chunk. Little tiny bit
05:58near the ground, colder than freezing. Look at the European model. 10 Celsius is 50 degrees Fahrenheit.
06:04The European says it's going to be raining in near 50 Fahrenheit, while the European is warm,
06:10the GFS still cold. So a huge disparity there. There's a lot of uncertainty with the
06:15Atlanta forecast. So I wanted just to make that real clear. And I'm going to go back to our graphics
06:19here just to wrap this up here. It's a fascinating story, I think, regarding the tricky challenges
06:24of Atlanta. We do have Atlanta in the significant ice. Freezing rain is a really difficult thing to
06:29deal with. We are very concerned about Atlanta. Just beware if the European is right. We may see
06:34warmer air charge in. And I'm going to quickly close with a look at the snowfall forecast here and get
06:39myself out of the way. Because we've got a bubble here of over a foot of snow in Iraqi weather forecast
06:45here. York, PA down to Charlottesville, Virginia. Big time snow coming in the northeast up there.
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