StormChat – Afternoon Forecast Discussion – 5-11-2022

Meteorologist Erik Dean talks about Thursday's threat for severe weather across the state.

Good Wednesday Afternoon. This morning we discussed the potential for some severe weather across Central and Eastern South Dakota for today. I threw a lot of jargon out and I want to go over what all that means.

The Storm Prediction Center in Norman, Oklahoma, has 6 different categories that they use to classify the severity of severe weather.

Spc Severe Threat Level

TSTM (Thunderstorm or 0 out of 5)
MRGL (Marginal or 1 out of 5)
SLGT (Slight or 2 out of 5)
ENH (Enhanced or 3 out of 5)
MDT (Moderate or 4 out of 5)
HIGH (High or 5 out of 5)

What does each one mean? Well, I am here to answer that for you.

TSTM: This is a general thunderstorm risk. Nothing severe expected, maybe a renegade thunderstorm or two. Lightning and flooding would be the main threats. Usually, you’ll see winds near 40 mph and small hail.

MRGL: This is a marginal risk for severe weather. I wouldn’t cancel plans over it. It just means isolated severe thunderstorms are possible. Just keep an eye on the weather just in case you get under something. The main threats here will be winds near 40-60 mph with hail up to 1” in diameter, and a very low tornado risk.

SLGT: If you see this, this is a slight risk for severe weather. Short-lived or isolated thunderstorms are possible. Main threats here would be maybe a couple of tornadoes, otherwise strong wind and hail near 1” in diameter, with some places seeing upwards of 2” in diameter.

ENH: This is an enhanced risk for severe weather. This category will consist of numerous severe storms that are more persistent. A few tornadoes are possible as well as several reports of wind damage and damaging hail near 1-2” in diameter.

MDT: Now we are getting into some extremely dangerous territory. This is a moderate risk for severe weather. Widespread, or long-lived thunderstorms are likely with the main threats being widespread wind damage, strong tornadoes, and hail near 2” in diameter.

HIGH: This one is rarely issued. (The last time one was issued was March 25, 2021, in Mississippi, Alabama, and Tennessee and March 17, 2021 in Mississippi, Alabama, Louisiana, and Arkansas. There were no high risks in 2020, and prior to that, the last one was in 2019, then 2017). This is tornado outbreak territory with long-lived, widespread and intense thunderstorms, destructive hail, widespread wind damage.

Thursday’s Forecast:

Day 2 Overview

As discussed in the previous post, Thursday has the chance to be worse as compared to today. Let’s analyze everything and I’ll give you my thoughts.

So as discussed earlier, for severe weather, temperatures need to be in the 70s.

Fc Temp Dma Sd
Again, East River is roasting again in the upper 80s – low to mid 90s. Temperatures: Check.

For dew points, I like to see them at 55 degrees and higher.

Fc Dew Point Dma Sd
They are well above 55 from Pierre to I-29 . Looking at Sisseton & Sioux Falls the dew points are in the mid 60s.

Let’s dive into Futurecast.

Ed Fc Radar Dma Sd Hd

Here’s the noon hour. Across the Black Hills region, rain chances will be on the increase. There may be a renegade shower or two at that time for East River. So you look at this and you’re like “Erik, what severe weather are you talking about? It’s sunny out!” And that’s the problem. The sun is going to allow for the daytime heating, which in this case will make the air even more unstable. This is one of those days where I would say “I’d much rather have a dreary overcast sky than plenty of sun.” Let’s start the clock again.
Ed Fc Radar Dma Sd Hd
By 5 PM, I-90 east of Chamberlain down to Charles Mix County will start to see the thunderstorms start to fire up.
Ed Fc Radar Dma Sd Hd
By 7:00 PM, it really starts cooking across I-29 from Roberts County all the way down to Union County, and well into Nebraska.

Ed Fc Radar Dma Sd Hd
By midnight, it’s out of the state, and we start to clear out. Now one thing I want to point out, if this system pushes through earlier in the day, that could mean some trouble. We really need to keep an eye on the timing, as it is critical.

So, let’s go through this again.

Day 2 Overview

We have the ENH (Enhanced or 3 out of 5) Risk of Severe Weather. It goes from Aberdeen, all the way to Southern Charles Mix County with a SLGT (Slight or 2 out of 5) Risk of Severe Weather stretching from Central & Eastern McPherson County down to Eastern Gregory County. The MRGL risk goes from Eastern Campbell County, SD. down to Eastern Todd County. I like the placement of this, but it would not surprise me if the SPC shifts everything a smidge east.

Day 2 Wind

Wind Threat: Not hatched, but it wouldn’t surprise me if it becomes hatched. The greatest chance for heavy wind is extreme Eastern South Dakota.
Day 2 Hail
Hail Threat: It’s already hatched for tomorrow for East River. The chances of 2″ diameter or larger is pretty significant.

Day 2 Tornado

Tornado Threat: The heaviest threat is across NE South Dakota. The threat for all of East River is still there as well, so don’t let your guard down.

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Categories: ConnectCenter1-Weather, Local News, Weather Daily