A severe threat of destructive winds, flash flooding and tornadoes is in store for states like Iowa, Illinois and Indiana
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00:00Joining me right now is AccuWeather severe weather expert Guy Pearson, and you know Guy, here we are in July, very
00:06summer-like pattern, and we're talking about severe weather. Of course, you were pointing out those thunderstorms to me in southern parts of
00:14Minnesota, but let's get into the ingredients, and number one, it's just widespread heat across the southern plains today.
00:22Yep, good morning everybody. Certainly, this time of year, we've got our big dome of heat, and that is built, and being 107 in Wichita today, it's certainly not the most comfortable
00:38weather to be in, but that large dome of heat plays a significant part into how it fuels the
00:44thunderstorms and the length of time in which these summertime thunderstorms potentially goes
00:49into the evening and overnight hours. Yeah, dew point temperatures, you know, well in the 70s.
00:55Just a steamy, steamy air masses well, Guy, and then we have the heat, we have the humidity.
01:01I'm showing the water vapor loop now, pretty vigorous upper level system across Saskatchewan right now.
01:09That's correct, and you know, that's been, when we were looking at the storms that developed from
01:14just overnight last night, you know, the pieces of energy that were helping drive some of that
01:20weren't nearly as pronounced as this one is. So typically, as you have a more pronounced or
01:25stronger piece of energy like this diving southeast and moving through the area, it
01:31will help set off, it provides that additional wind energy aloft to help keep those, you know,
01:36the thunderstorm generation and development and movement going. Yeah, in fact, I want to show you
01:42a low-level jet, and you and I were just talking about this. Oftentimes, you don't see this much
01:47energy in at around 5,000 feet because the more energy, the more wind, the more energy and more
01:52likely severe weather. I'm going to stop this later on tonight, and we start seeing these
01:57dark purple showing up across Illinois, Indiana, and then during the overnight hours,
02:02the wind's actually increased, Guy.
02:07That is correct. Typically, that low-level jet does increase during the overnight hours,
02:12and so in a situation like this, we have that strong piece of energy from the north. You've got
02:16a lot of thunderstorm development in our complex that is looking to develop over Iowa later today,
02:23and, you know, that piece of energy is enough to drive it and keep it going long enough to where
02:28then the, you know, the low-level jet from the south can kick in during the overnight hours
02:33and continue to feed that moisture and that heat into the storm system itself, and then that'll,
02:38part of that is what will help it prolong and continue through the evening and into the
02:45overnight hours once again. Let's talk about Chicago, Guy. We're talking offline. Here comes
02:49a line of thunderstorms coming in around 7, 8 o'clock. I was certainly worried about Chicago.
02:55You think that the higher threat for those widespread destructive winds may be just off to the south?
03:02Yeah, typically, you know, one of the things that we're looking at model bias-wise is positioning
03:07things too far north, so certainly Chicago, you're still in it. You still should expect
03:13severe thunderstorms with damaging winds, but the strongest winds in all likelihood will remain
03:19south of Chicago, but could cut a pretty good swath through, you know, sort of north-central
03:25and central Illinois later tonight as the storms progress and move southeast. Not often times
03:33you've made the decision, you and the Severe Weather Forecast Team, AccuWeather local storm
03:38max of 105 miles per hour, wind gusts 80 to 90 miles per hour. We're worried about a deratio, aren't we?
03:47Yeah, we are, unfortunately. This is one of those scenarios that, you know, thunderstorms, when
03:52especially in microburst scenarios or longer duration wind events like this, where you have a
03:58lot of wind energy aloft, that wind energy does make down to the surface, and you can have wind gusts
04:03in microbursts and bowing segments of the severe thunderstorm anywhere between 100 and 120, and
04:09that's generally, you know, what lays over a lot of trees and things like that. You know, we do have
04:15the AccuWeather local storm max of 105, so this is certainly a complex to keep an eye on later
04:21tonight because there looks to be certainly a swath of damaging winds. AccuWeather severe
04:28weather expert, Guy Pearson. Guy, thanks for joining us, and keep us updated.