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Dangerous heat in the middle of the country and thunderstorms in the Northeast may seem like two completely separate forecasts, but they're actually linked. AccuWeather's Geoff Cornish explains how.
Transcript
00:00On the forecast feed, we're going to be talking about two unrelated thoughts that actually
00:05are connected to one another.
00:06We have heat in the Great Plains, it's going to be a big story, and also the return of
00:11some strong thunderstorms eventually, after a nice prolonged dry, quieter spell in the
00:16Northeast, we get back into it next week.
00:19They are related though, and I'll show you how.
00:21Before we get into that though, first a quick look at three big headlines for the weekend,
00:26so I'll get my head out of the way.
00:28We're looking at stormy weather in the Southeast, frequent downpours, lightning, and some localized
00:33flash flooding will be a concern in the Southeastern US.
00:36Another big headline this weekend, sizzling heat in the Plains.
00:40Some areas will be approaching record highs, we'll give you a few examples Thursday, Friday,
00:44and then we'll jump ahead to Sunday.
00:46There's still a wildfire threat in the Northwest that will actually be escalating as well, so
00:50the weekend is going to be actually very pleasant in the Northeast.
00:54But first off, let's talk about some of these near record highs in the Plains, and then I'll
01:00get into the computer models.
01:01I'm also sneaking a little bit of Florida in here, maybe perhaps a little awkwardly,
01:05but the record heat, or near record heat is occurring initially in Texas and parts of
01:10Florida Thursday.
01:11You can see Borgia, Texas 106, 104 in Amarillo, and then also Tampa may make a run at a record
01:18high.
01:19Before we get too far into this, I want to show you why this is happening.
01:23And overall, you can see a couple of different competing factors.
01:27We're going to go up about 20,000 feet up into the atmosphere, 500 millibars, and we have
01:32a strong upper level ridge of high pressure.
01:34By the way, this sneaky guy here just to the south is actually, again, the center of circulation
01:42could form a little farther south, but a loft is actually farther south.
01:45This is, that's Bertha moving west into Thursday morning.
01:50But overall, there's a big ridge of high pressure that is keeping areas unaffected by Bertha really
01:56hot here over parts of the southern plains.
01:59And as we give you another example of what some of this looks like here, again, here is
02:06another model.
02:07This is the NAM that also takes the upper level low pressure system associated with Bertha
02:11south, and then also the European generally south.
02:15So we've got to keep an eye on the future of this storm.
02:16But regardless, there's going to be a lot of heat that builds.
02:19And watch, after that storm fades, this big ridge of high pressure aloft, I'm going to
02:26circle it in a different color so you can see it a little more clearly.
02:30It's going to be pretty expansive.
02:31This is the 594 decameter line.
02:35So basically, talking about like a mountain of air, very, very high bubble of air in the
02:41atmosphere.
02:42And remember, hot air expands, colder air constricts, and this is like a mountain of
02:47air that expands.
02:47In fact, if we were to compare the footprint of the 594 line, if you think about almost
02:52like a topographical map, it's a little smaller this Wednesday evening.
02:56Fast forward, look how big it gets.
02:58This is a big swollen mountain of air, basically, over the south central U.S. into Friday night
03:03and Saturday.
03:04And then fast forward into Sunday, it holds strong, although by early next week it begins
03:09to get kind of tampered down from the north.
03:11Here's the European, and it has a fairly sizable ridge.
03:14I could just plot this high right over the center of it.
03:17So this is responsible for a lot of the heat in the short term.
03:20And as we go back to our graphics, I showed you some of the record-challenging highs for
03:25Thursday.
03:25Here's Friday, 106 in Roswell, New Mexico.
03:28That would tie a daily record, 103 in Amarillo, Texas would tie the record from just three years
03:32ago.
03:33And we're still pretty steamy in some other areas.
03:35And then let's fast forward to Sunday, I showed you that that big mountain of air is
03:38still present.
03:40106 all the way north into Rapid City, South Dakota.
03:42You might say, South Dakota is typically cool.
03:44They're landlocked, and they can have some tremendous extremes.
03:47So the daily record high for Sunday, for Sunday's date, which I'm trying to think what day it
03:53would be, 22nd, 3rd, 4th, 26th of July, the record high is 104 from 2021.
04:00They can see some tremendous heat there, but 106 would break the daily record.
04:03Amarillo, Billings, Montana, 102, the record 101 for the same date.
04:07Casper, Wyoming, 100 degrees.
04:09So tremendous heat.
04:10Denver, you're going to make a run at NERA record as well.
04:13And you can see, big picture, Friday, Saturday, Sunday, we have a big ridge of high pressure.
04:19Remember that mountain of air was kind of generally in that area as I'm kind of redrawing it on
04:24our forecast map.
04:25But you'll notice there's also this jet stream that eventually is going to begin to send
04:31some disturbances from Canada around the perimeter.
04:35And there's even a zone with some thunderstorms on the northeastern perimeter of the ridge
04:39of high pressure in the south central U.S.
04:41But overall, the storm track is going to get more active here.
04:44And we're going to begin to see some disturbances.
04:47Here you can see, while there is a large zone of low pressure to the north over the Hudson Bay,
04:56we still have this contrast with high pressure to the south.
05:00And as we move into next week, we're going to begin to see that disturbance to the north
05:05send some energy across the Great Lakes, these little ripples of energy.
05:09I know these bright colors, they look a little chaotic.
05:11This is a measure of vorticity or spin in the atmosphere.
05:15And these disturbances are going to lead to pockets of lift in the atmosphere.
05:20If you're east of one of them, you're in a posture of lift in the atmosphere.
05:23Here's another one, be some extra lift in the atmosphere east of there.
05:26So that's going to produce more showers and thunderstorms.
05:28Here's kind of a less grainy looking version.
05:31The European model has kind of lower resolution.
05:33So it shows more definitively this disturbance coming in right across the area with recent wildfires.
05:39You're going to see another round of storms there.
05:40And east of there, as that area of lift is approaching you,
05:43you can look out for thunderstorms in the Great Lakes Sunday night and Monday.
05:46And then Monday evening, look at this, we have a pretty sharp trough.
05:50And east of there, this is the area where we could expect to see
05:53some thunderstorms.
05:54So the actual modeling here is the GFS.
05:58The timing is a little different between the two models.
06:01Storms Sunday night into early Monday morning in the Great Lakes
06:05and then into the northeast Monday evening in the Ohio Valley.
06:08That's the GFS.
06:10The European, it shows a little bit more of a delayed start Sunday night in the Great Lakes.
06:15Monday, it's more of Michigan Monday night into the Great Lakes region
06:18and it'd be more of a Tuesday impact for the northeast.
06:21So there's still a little bit of question as to the details.
06:24But what we want you to know is sometime between Monday and Tuesday,
06:27the northeast will get back into some strong thunderstorms.
06:29But in the meantime, you can see we're running cool.
06:32This is a statistical look at how temperatures compare to normal.
06:35Cooler than normal in the Ohio Valley for a bit.
06:37But watch the heat build up into the northern part of the plains
06:41into the weekend with some record highs coming.
06:43Pretty significant heat coming your way into the Dakotas and Montana later this weekend.
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