00:00Well, the Atlantic is quiet. Pacific's certainly active. We've been talking a lot about that
00:05with impacts in Hawaii there, as Lowell makes a side-swiping brush. The Atlantic, by the way,
00:13this is our third Labor Day in a row with no-name storms active, and that's pretty amazing. You have
00:20to go back to the 1930s, 1937, 1938, 1939, to find the last three Labor Days with no-name storms
00:27in
00:28the Atlantic for three consecutive years. That was long before the satellite era even began. Pretty
00:32impressive. Because the Atlantic has so much wind shear and large patches of dry air, I wanted to
00:38focus the forecast feed over the central and into the eastern U.S., looking at a conflict in air
00:46masses and how that's going to drive some strong thunderstorms this week. So we begin with a big
00:52zone of heat, and we've been discussing the near-record highs in some areas as we move through
00:59Tuesday, Wednesday, even into Thursday. A lot of the near-record highs are kind of scattered in the
01:05southern half of the red zone, and then we're going to see a slightly more spotty distribution
01:11by Thursday, so near-record highs generally kind of from parts of the south-central U.S. into the
01:15lower Mississippi Valley. And we've had a delightful stretch here in the northeast. Things are looking
01:20good for the remainder of this Labor Day. High pressure here. But overall, the heat's going to
01:26gradually return just for a day or so. Won't be widespread stifling heat, but it will get warmer
01:34into the 80s and some spots in the mid-Atlantic down into the low 90s on Wednesday. And the humidity
01:40will sneak up on us as well. So when we find the conflict in air masses here, the boundary between
01:47very warm and unstable and humid air versus some cooler and less humid air, we begin to look for
01:55thunderstorms. And we're going to find one of these fronts, a cold front that drives on into the
02:00Midwest here at midweek. And that's going to be setting the table for some strong thunderstorms,
02:05again, southeast of that location here. So I wanted to switch over to the modeling to give us a better
02:11view of that. And as we switch over to that, I can show you what we're looking at. So let's
02:17begin
02:18with going upstairs. And overall, here, let's take us to Tuesday afternoon. Here you can see the zone
02:26of high pressure, a big 594 thickness line. This big, this height line, that's an indication of where
02:36the upper level high pressure system is set up. Think of this as like a mountain of air. Hot air
02:41expands. Cold air is more constricted. So you have a mountain of hot air out there across much of the
02:48south central into the southeastern U.S. and the core of the heat's mainly between I-75 and I-25.
02:55So a lot
02:55of this is kind of between the Appalachians and the Rockies. And as we move forward in time, we have
03:01another big feature on the map. It's a disturbance in the northern branch of the jet stream. And this
03:07is going to be driving a front through the region here. So Tuesday and Tuesday night. You can see a
03:13few of these disturbances. There are a couple of them. They're a little bit out of phase. Here's one.
03:16Here's another. They're a little discombobulated. And as we move forward in time, they do kind of
03:22phase. The southern, the slower one catches up with the northern one. But it happens so far north
03:29that it's going to be way up into Canada, deep up into Canada. So what we're going to find
03:34is that this disturbance, the driver behind our severe weather producing thunderstorms in the
03:41plains, northern plains initially, Monday night into Tuesday, we're going to see it aboard the
03:45Midwest. The upper level driver, I'm going to trace the path that the low pressure system takes.
03:50We are near Lake Winnipeg. And I'm going to take us into Thursday and look at the general
03:56flavor here by Thursday evening. We're kind of traveling northeastward. It's not
04:03hugging the U.S. coastline. It's pulling north. So what we're going to find is that the storms and
04:08the upper level support for these storms that are going to be accompanying a front that does make it
04:13into the northeast, the upper level winds are going to become a little weaker as we get into
04:19Wednesday and Thursday because it's going to be more divorced from the storm driver, the energy
04:23aloft, farther to the north. Instead of it being near the international border, it's going to be
04:27way, way up north of Vermont. So, and there's a little, another subtle feature that kind of feeds
04:33into the back end of this, this little guy, this disturbance here. If we go back, it's actually a
04:41separate feature that's going to kick the system a little bit farther each with a little more
04:47gumption. But it's so far north by the time that happens. So here is something called the shift of
04:52tails. It sounds kind of European, doesn't it? It's a statistical way of looking at how unusual
04:57the air mass is. And we get into the purples and the magentas. That is really unusually hot air. And
05:04the deep greens up into Idaho, cooler than normal air for this time of the year. So there, here we
05:09go
05:09through, uh, through Tuesday and Wednesday. And you begin to see, uh, the yellows return to the
05:14northeast. It's going to get hot again on Wednesday, but just for a brief time. And then that front knocks
05:17us back down. But the warmth is going to be fuel for some of these storms. We have blisteringly hot
05:24air
05:24in the central plains Tuesday. Look at this. You can see modeling that it takes. Now there's a lot of
05:29variety between 108 up there in Manhattan, Kansas versus 98. That's the model spread here. Uh, the
05:35GFS tends to run a little hot, but you can see some of the contrast here. And then we begin
05:39to see the
05:40heat get suppressed a little farther south as a front swings through, uh, the northeast. So what I
05:46wanted to highlight was the instability here and the potential for some thunderstorms. And we're looking
05:50at areas around, uh, Omaha and Des Moines. This is where we have some somewhat limited wind shear,
05:57but there's plenty of lift in the atmosphere on Tuesday. So Tuesday, gusty winds and hail
06:02accompanying some storms there in Iowa and surrounding states. Let's go to Wednesday.
06:07Here we go into the, uh, the Midwest and the Ohio Valley. So areas like Ohio and Indiana and places
06:14like Illinois, strong storms, damaging wind and hail are the main concerns. Not enough shear for many
06:19tornadoes though, because remember the disturbance aloft is going to be way up in Canada. And by the time we
06:24get to Thursday, there will be some storms in the northeast, but the instability is a little more
06:29limited Thursday in the interior northeast and Friday into the mid Atlantic. Uh, so again,
06:34the upper level disturbance that's going to be driving these storms will be so far north that
06:39we're going to expect some storms, but they may not be terribly intense by the time we get to
06:44Thursday in the northeast, damaging winds for some, at least by then.
