00:00In the forecast feed, we have a lot to talk about regarding severe thunderstorms ramping right up into Easter weekend.
00:07And we're going to be dealing with, again, some very heavy rain on Easter Sunday in the northeast along I
00:12-95.
00:12But in the short term, let's take a look at what's going on here this Wednesday night.
00:18And here we are with some heavy thunderstorms rumbling, escalating late in the evening into the overnight hours through the
00:25southern plains.
00:25We're going to look at the modeling behind this and track this setup here that's going to really ramp up
00:32into Thursday.
00:33Thursday, we have a larger zone.
00:36We've filled in the gap there in Chicago with a moderate risk, two out of four, on the AccuWeather four
00:41-tiered severe threat index.
00:43So let's take a look at the modeling here and what's driving this.
00:47Big picture, we have two separate storm systems to close out this sequence of busy days here this week.
00:55Let's just kind of press pause Thursday at 2 p.m.
00:59Here's one of them.
01:00You can see this trough.
01:01It's partially negatively tilted.
01:03It's a little bit negatively tilted.
01:04So that's storm system number one.
01:07And then we have number two here.
01:09Strong zone of low pressure moving through parts of the Great Basin.
01:14And that's going to be sliding east, digging down a bit here into the plains.
01:20So one lifts up into the Midwest here.
01:22It is a negatively tilted trough on Thursday.
01:25Say negatively tilted.
01:26We're talking about the tilt, the way it's kind of sloped northwest to southeast, tilted down and to the right.
01:33Even on a curved map, slightly more east on the south side than it is on the north side.
01:39But that storm system is going to be eventually lifting up and out.
01:45And it becomes less of a driver later in the week while the new storm system digs in.
01:50And this one is going to be on a trajectory.
01:52So again, one lifts up and out here.
01:56And another one digs down into the plains.
01:59So we're dealing with one storm system exiting and then the caboose.
02:02This is the big one here at the end of the week.
02:04Friday, Friday night into Saturday rolls right into the plains emerging from the Rockies.
02:09And that's the big driver in the late week severe weather threat.
02:13So we have kind of two days with storm system number one.
02:17That's tonight into Thursday.
02:19Here we are late tonight.
02:20Strong storms breaking out there in the southern plains.
02:22And then into the day Thursday.
02:25Thursday we're going to be dealing with some strong storms.
02:27Now the amount of precipitation you may be seeing may not kind of catch your eye.
02:32But there is a lot of wind energy out there in this area here between the warm front and the
02:37cold front.
02:39We call this the triple point.
02:41And some even call it Larco's Triangle in that area there, which includes Chicago.
02:46That's a pretty volatile place to be on Thursday.
02:50Here's another depiction of that.
02:51Again, it's not about the amount of precipitation.
02:53We're more concerned about the chance for rotation within storms, an isolated tornado threat here.
02:59And again, this area here between the warm front and the cold front with storm system number one on Thursday
03:07causing trouble in the Midwest.
03:09So when we look at the instability, here's the giant wild card.
03:14How much instability will there be?
03:17The jet stream dynamics are strong.
03:19There's a lot of wind shear, twisting of winds with height.
03:22What we're lacking a little bit is instability.
03:25This is CAPE, Convective Available Potential Energy.
03:29It's an acronym.
03:29And it basically is expressing the contrast between warm, humid air near the ground and much colder air aloft.
03:37Warm, humid air is less dense than colder air.
03:41And you get these bubbles of warm air to rise.
03:43They become updrafts.
03:44Now, you'll notice that on the mapping here Thursday evening, this is the GFS.
03:50You're going to see a lot of blue.
03:52And the blue on the scale is less than 1,000.
03:56It's 1,000 joules per kilogram.
03:58That's the unit of measure.
03:59So we're looking at maybe 500 to 750 joules per kilogram of CAPE here in Illinois and much greater instability
04:06down into Texas where you're going to have some taller thunderstorms.
04:09That's the GFS.
04:10Let's look at the NAM, another opinion.
04:12Slightly more CAPE here early, but then you can see Thursday afternoon and evening there's an axis of this in
04:18which we do crack above 1,000 joules per kilogram into areas north of St. Louis and into Rockford, Illinois.
04:24That's a little bit more unstable.
04:25Here's the European.
04:26Again, it's kind of maybe splitting the difference between the two, where if we take it literally, 1,000 joules
04:32per kilogram, kind of limited to areas south of Peoria.
04:35So that's one thing that we're keeping an eye on.
04:38And again, what we will be limited by will be limited instability, but there's plenty of shear, so the updrafts
04:43will probably get going just enough to spark a few tornado threats and damaging winds as well.
04:48Behind that, the next storm system, the caboose rolls in.
04:52Remember, we had one storm system lifting, and now the next one digs down Wyoming into the plains, Friday to
04:59Saturday.
04:59This is the final one in this sequence of stormy days.
05:01So what does this do?
05:03Here we go through Friday.
05:04Friday early afternoon, not much.
05:06Late afternoon, here we get into business in the southern plains.
05:09There's your cold front, and there are the storms erupting associated with that.
05:13So Friday evening and Friday night, there they are.
05:15It looks pretty aggressive with the European depiction of things.
05:18Let's take a look at this here.
05:20When it comes to the parameters that we're facing on Friday, we have medium amounts of moisture, medium amounts of
05:27warmth.
05:27There's no shortage of that here down into the southern plains.
05:31And we have high amounts of jet stream energy.
05:35So where does that land us?
05:36With a medium risk for a large area from Oklahoma up into southern parts of Iowa on Friday afternoon and
05:42night.
05:43This is Friday.
05:44This is the final storm system in the sequence.
05:46And then instability wanes a bit as this slides east into Saturday.
05:50So that's something we have to track.
05:52By the time this reaches East Coast Easter Sunday, and we do want to acknowledge this is Passover as well,
06:00for our friends who are celebrating that,
06:02it's going to be a very wet time along Interstate 95, drenching downpours, drenching downpours.
06:08And back to the modeling, if we go back to the instability, you can see it really Saturday, there's not
06:13a whole lot of instability in the Ohio Valley.
06:15There's some, there will be thunderstorms.
06:18The NAM is a little more aggressive into Ohio Saturday.
06:21The European, pretty limited in some of these areas.
06:24So those are some of the disruptions that we're facing.
06:26And then there's very limited instability back into the East Coast.
06:29Final thing I wanted to mention.
06:30There's a cold side to this.
06:32And look at this.
06:33We're looking at some accumulating snow.
06:35Two rounds of it.
06:36Wednesday evening through Thursday into Friday morning.
06:40That's storm system number one.
06:41We got some ice in storm system number two.
06:45This is going to bring freezing rain and even more snow into Saturday evening.
06:49That's your forecast feed.
06:51You got it.
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