00:00Well, the Atlantic is quiet. Pacific's certainly active. We've been talking a lot about that with impacts in Hawaii there,
00:07as Lowell makes a side-swiping brush.
00:12The Atlantic, by the way, this is our third Labor Day in a row with no-name storms active, and
00:19that's pretty amazing.
00:20You have to go back to the 1930s, 1937, 1938, 1939, to find the last three Labor Days with no
00:27-name storms in the Atlantic for three consecutive years.
00:30That was long before the satellite era even began. Pretty impressive.
00:33Because the Atlantic has so much wind shear and large patches of dry air, I wanted to focus the forecast
00:39feed over the central and into the eastern U.S.,
00:44looking at a conflict in air masses and how that's going to drive some strong thunderstorms this week.
00:50So we begin with a big zone of heat, and we've been discussing the near-record highs in some areas.
00:58As we move through Tuesday, Wednesday, even into Thursday, a lot of the near-record highs are kind of scattered
01:05in the southern half of the red zone,
01:07and then we're going to see a slightly more spotty distribution by Thursday,
01:12some near-record highs generally kind of from parts of the south-central U.S. into the lower Mississippi Valley.
01:17And we've had a delightful stretch here in the northeast.
01:20Things are looking good for the remainder of this Labor Day.
01:23High pressure here, but overall, the heat's going to gradually return just for a day or so.
01:30Won't be widespread stifling heat, but it will get warmer into the 80s in some spots in the mid-Atlantic,
01:37down into the low 90s on Wednesday.
01:39And the humidity will sneak up on us as well.
01:42So when we find the conflict in air masses here, the boundary between very warm and unstable and humid air
01:50versus some cooler and less humid air,
01:54we begin to look for thunderstorms.
01:56And we're going to find one of these fronts, a cold front that drives on into the Midwest here at
02:01midweek,
02:02and that's going to be setting the table for some strong thunderstorms again southeast of that location here.
02:08So I wanted to switch over to the modeling to give us a better view of that.
02:12And as we switch over to that, I can show you what we're looking at.
02:16So let's begin with going upstairs.
02:20And overall, let's take us to Tuesday afternoon.
02:25Here you can see the zone of high pressure, a big 594 thickness line, this height line.
02:34That's an indication of where the upper-level high-pressure system is set up.
02:38Think of this as like a mountain of air.
02:40Hot air expands.
02:42Cold air is more constricted.
02:44So you have a mountain of hot air out there across much of the south-central into the southeastern U
02:50.S.
02:50and the core of the heat is mainly between I-75 and I-25.
02:55So a lot of this is kind of between the Appalachians and the Rockies.
02:58And as we move forward in time, we have another big feature on the map.
03:03It's a disturbance in the northern branch of the jet stream.
03:07And this is going to be driving a front through the region here.
03:10So Tuesday and Tuesday night.
03:12You can see a few of these disturbances.
03:14There are a couple of them.
03:14They're a little bit out of phase.
03:16Here's one.
03:17Here's another.
03:18They're a little discombobulated.
03:20And as we move forward in time, they do kind of phase.
03:23The southern, the slower one catches up with the northern one.
03:26But it happens so far north that it's going to be way up into Canada, deep up into Canada.
03:34So what we're going to find is that this disturbance, the driver behind our severe weather-producing
03:40thunderstorms in the plains, northern plains initially, Monday night into Tuesday, we're
03:44going to see it aboard the Midwest.
03:46The upper-level driver, I'm going to trace the path that the low-pressure system takes.
03:51There we are near Lake Winnipeg.
03:52And I'm going to take us into Thursday and look at the general flavor here by Thursday
03:58evening.
03:59We're kind of traveling northeastward.
04:02It's not hugging the U.S. coastline.
04:04It's pulling north.
04:05So what we're going to find is that the storms and the upper-level support for these storms
04:11that are going to be accompanying a front that does make it into the northeast, the upper-level
04:17winds are going to become a little weaker as we get into Wednesday and Thursday, because
04:20it's going to be more divorced from the storm driver, the energy aloft, farther to the north.
04:25Instead of it being near the international border, it's going to be way, way up north of Vermont.
04:31And there's another subtle feature that kind of feeds into the back end of this, this little
04:35guy, this disturbance here.
04:39If we go back, it's actually a separate feature that's going to kick the system a little bit
04:46farther east with a little more gumption.
04:48But it's so far north by the time that happens.
04:50So here is something called the shift of tails.
04:53It sounds kind of European, doesn't it?
04:54It's a statistical way of looking at how unusual the air mass is.
04:59When we get into the purples and the magentas, that is really unusually hot air.
05:04And the deep greens up into Idaho, cooler than normal air for this time of the year.
05:08So here we go through Tuesday and Wednesday.
05:12And you begin to see the yellows return to the northeast.
05:15It's going to get hot again on Wednesday, but just for a brief time.
05:17And then that front knocks us back down.
05:19But the warmth is going to be fuel for some of these storms.
05:22We have blisteringly hot air in the central plains Tuesday.
05:26Look at this.
05:27You can see modeling that it takes.
05:29Now there's a lot of variety between 108 up there in Manhattan, Kansas versus 98.
05:33That's the model spread here.
05:35The GFS tends to run a little hot.
05:37But you can see some of the contrast here.
05:39And then we begin to see the heat get suppressed a little farther south as a front swings through the
05:44northeast.
05:45So what I wanted to highlight was the instability here and the potential for some thunderstorms.
05:50And we're looking at areas around Omaha and Des Moines.
05:53This is where we have some somewhat limited wind shear, but there's plenty of lift in the atmosphere on Tuesday.
05:59So Tuesday, gusty winds and hail accompanying some storms there in Iowa and surrounding states.
06:06Let's go to Wednesday.
06:07Here we go into the Midwest and the Ohio Valley.
06:11So areas like Ohio and Indiana and places like Illinois.
06:15Strong storms.
06:16Damaging wind and hail are the main concerns.
06:18Not enough shear for many tornadoes, though, because remember the disturbance aloft is going to be way up in Canada.
06:24And by the time we get to Thursday, there will be some storms in the northeast, but the instability is
06:29a little more limited Thursday in the interior northeast than Friday into the mid-Atlantic.
06:34So, again, the upper-level disturbance that's going to be driving these storms will be so far north that we're
06:40going to expect some storms, but they may not be terribly intense by the time we get to Thursday in
06:46the northeast.
06:46Damaging winds for some, at least by then.
06:48That's your forecast feed.
06:49I'm going to see you next week.
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