00:00Destructive hail, widespread damaging winds, flooding is going to be a concern, and we're projecting one to two dozen tornadoes.
00:09We're, of course, talking about Friday afternoon and Friday night.
00:12I want to show you the severe weather threat.
00:14I'm going to break it down here on the feed and show you why we're so concerned and why we
00:18have issued a high risk.
00:23There is the area that we're talking about. What's also significant is how large the moderate risk for severe weather
00:31is.
00:32It goes all the way up from Rhineland, Wisconsin, down to Oklahoma City.
00:36But again, right in here, there's your high risk from about Independence, Kansas, to Dubuque, Iowa, and probably just to
00:46the west of Madison.
00:47All right. Why are we so impressed with the severe weather for Friday?
00:52Well, let's go over the ingredients. The first thing you always look for.
00:56Do you have warmth? Do you have low-level moisture? You can check that off.
01:00Let me show it to you here on the modeling here.
01:03So this is tomorrow afternoon at around 2 o'clock.
01:06Look at the surge of warmth coming all the way up in the Wisconsin.
01:09The 80-degree line gets close to Chicago by tomorrow afternoon.
01:13So it may be mid-April, but as far as the weather is concerned, it's June, mid to late June
01:21on Friday.
01:23Also, dew point temperatures, what's the threshold? About 60.
01:26Take a look at our dew point temperatures. I mean, this is very high.
01:30This green here, right in here, is 65 degrees or greater.
01:36This 60-degree line, isodrositherm, that's a line of constant dew point temperature.
01:43It goes all the way up in the Wisconsin, 60.
01:45And you also notice, look how dry it is.
01:48This is a pretty strong dry line coming in here, where dew points go from the 30s to the 60s
01:55like that.
01:56So that's ingredient number one.
01:58All right, let's talk about the energy.
02:00Let's look at the 500 millibar here.
02:02This is what we're looking at.
02:04Very strong dip in the jet stream here across the Pacific Northwest.
02:10Today, watch that come across the area and then sweep through.
02:14See, right in here, Friday afternoon, Friday night.
02:18So what's going to happen is, you're going to have a lot of wind energy here on the southern tail
02:22of this 500 millibar trough.
02:25And you'll notice all the red, too, showing you the wind energy.
02:28Another way to look at it is look at the low-level jet.
02:32And in particular, how it increases.
02:35Watch this.
02:36Watch this area in here.
02:37You do have some wind all day.
02:39But I want you to zone in on this zone in here, how you go from about 30 knots right
02:46in here.
02:47Watch it increase.
02:48This is from 2 o'clock.
02:51Boom.
02:522 o'clock, 5 o'clock.
02:54And then watch how it goes right in there.
02:55All of a sudden, you're going up at about 40, 50 knots.
03:00So not only do you have a lot of wind, but it's an increase in wind, right?
03:04Like water through a pipe.
03:05If you restrict the pipe, the water comes out faster.
03:08That's what's happening.
03:09So that's going to increase your upward motion as you go through the afternoon.
03:14I mean, that is a lot of increased motion.
03:18Just to show you, just to show you how unstable the atmosphere is,
03:26we look at something it calls CAPE, convective available potential energy.
03:32Now, it sounds very complicated.
03:34But the higher the number, the more unstable the atmosphere is going to be.
03:40I want to show you where we're at here.
03:42This is Friday morning.
03:43Right off the bat, you could see this.
03:45You're starting to get in these areas.
03:47And, you know, you're above 1,000 on this number.
03:51That's good enough for severe weather.
03:53I want to show you, watch how it increases Friday afternoon.
03:56Boom.
03:57I mean, now, this is from the NAM.
03:59I tend to trust that when it comes to convection.
04:02But look at this zone in here where you're in the orange and the red.
04:07Remember, I talked about, you know, 1,000 would be a pretty good number here.
04:12You're in this air territory between 2,500 and about 4,500 at joules per kilogram.
04:21You don't really have to worry about that.
04:22But that just shows you how unstable this atmosphere is.
04:27So you've got the warmth and humidity.
04:30And because you have that dip in the jet stream coming in,
04:33you're going to have a lot of colder air aloft.
04:36That makes for a very, very unstable atmosphere here.
04:41Now, let me show you the surface map, and you can see we'll put it all together here.
04:46I was talking about the dew point temperatures here, but you also have this.
04:51You have a strong cold front.
04:52That's why you're getting that.
04:53So you've got your cold front right in here.
04:56All right.
04:57There it is.
04:58That's in the morning hours, right?
05:00Let's go to about 2 o'clock into the afternoon, and then we'll take it to the evening.
05:06So there's 2 o'clock.
05:08Watch this.
05:08You see what's going on here?
05:10You're not getting – and here we are at 2 o'clock, and you don't see any green here at
05:15all.
05:15You have no precipitation.
05:17Watch how it explodes in about six hours right here.
05:23Watch it right in here.
05:25Look at that.
05:26And here's why.
05:27You've got this strong cold front.
05:30And again, you have the difference in not only temperature but humidity right in here.
05:36And this whole area, this whole area just explodes with rain and thunderstorms between about 2 o'clock and 8
05:46o'clock tomorrow afternoon.
05:48I'll take off the front so you can see it, and I'll go over it again.
05:51Watch how it explodes from nothing to that in about six hours.
05:56So that means you have a tremendous upward motion field.
05:59The other thing to consider in this area is you've got these little areas of low pressure in here.
06:06And typically what they tend to do is they can produce directional shear, and you've got to worry about tornadoes
06:12with this.
06:13And that's why we're talking about one to two dozen tornadoes, not only in here but across Iowa.
06:24So when I go back to our map here, and this is what we'll end with, this is why we
06:30have the high risk.
06:31You're going to see golf ball size, baseball size hail, widespread damaging winds, and we think one to two tornadoes.
06:39The peak between 3 o'clock and 9 o'clock, it will then diminish overnight.
06:44Watch for the flooding as well.
06:46And that's the feed.
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