StormChat – Morning Forecast Discussion – 5-11-2022
Meteorologist Erik Dean breaks down the possibility for severe weather across parts of the NewsCenter1 viewing area.
This Day in Weather History: On May 11, 1920: The second worst flood on record occurred as Rapid Creek crested six feet above normal flow, washing out all low bridges, damaging several of the railroad bridges coming into Rapid City, and causing $200,000 in damage and six deaths.
Good Wednesday Morning. I hope you have had a wonderful week so far. Let’s dive into the forecast as we have a lot of stuff to talk about.
First, the Storm Prediction Center in Norman, O.K. has posted the majority of the NC1 Viewing Area under some kind of categorized risk for Severe Weather. We’ll talk about the Black Hills region in this blog post, but I want to focus on Central & Western South Dakota as they are under a MRGL (Marginal) Risk for Severe Weather (or a 1 out of 5 on the scale) with some places East River under a SLGT (Slight) risk for Severe Weather (2 out of 5). As you know me pretty well, I don’t like to just regurgitate information. I like to thoroughly analyze the data, and I want to give you the best and most accurate forecast possible.
There’s a reason as to why I am throwing a lot of this information out this early in the morning. I’ll tell you why at the end of this blog post.
The things I look at when analyzing the threat for severe weather are as follows:
1- I like to see temperatures at least in the 70s. Mid 70s and higher to be exact.
2- I like to see Dew Points at LEAST in the mid-50s.
3- I like to see some kind of forcing mechanism.
The first thing we are going to look at are the temperatures as we roll into the afternoon.
As you can see, temperatures will be well above the 70 degree mark. Upper 80s even low 90s will be the rule East River. Temperatures above 70: Check.
How about Dew Points 55 degrees and above?
Let’s use Futurecast, and time everything out hour by hour.
By 3 PM, look at SE South Dakota near Yankton. See how the thunderstorms start to fire up? Watch what happens when we start the clock again.
1:00 AM Thursday, thunderstorm chances start to fire up across the Black Hills region, and over towards the Pierre & Chamberlain area as well.
Then by 6:00 AM Thursday, it’s basically just a nice, steady rain across the area.
We’ve discussed this before; but one thing that you need to pay close attention to on the maps below is this; sometimes the Storm Prediction Center puts the black hash marks on these maps. (You’ll hear me refer to this as the “Hatched Area”) Basically it means there’s a significant, or a greater threat, of the type of severe weather that is discussed at that time.
Hail: If you see a hatched area for hail, it means it’s likely that large hail will occur within the area. (2” in diameter or larger is considered large, or damaging hail.)
Tornado: The hatched area on a tornado outlook means a category EF-2 or higher is possible.
Wind: The hatched area for damaging wind means winds 74 mph winds or greater is possible.
**All of these are within a 25 mile of a specific point in the highlighted area.**
Notice the heavy wind percentage is at 30% percent extreme East River (hatched), with a 15% across the rest of East River, and a 5% across the majority of the state.
There’s that hatched area I was talking about, stretching East River and going into parts of Minnesota, extreme NW Iowa and NE Nebraska. 15% percent hatched is highlighted in the areas shaded in yellow, with a higher chance hatched (30%) in the areas shaded in red.
There is a chance for a spin-up or two East River. The heaviest threat is in yellow across I-29. The brown shading is a slightly lower threat, and same with the areas shaded in green. Now, I need to reiterate something as every time I say there is a “chance for a Tornado.” It’s just that, it’s a chance, it does not mean you’re going to see one. It just simply means the conditions are favorable to produce a tornado or two.
My Thoughts: Based on everything that I have discussed in this blog post, I completely agree with the Storm Prediction Center’s decision of placement of everything. So, the big thing is to keep an eye on the conditions for today.
So, why did I throw all this information out this early in the morning? Because not only do we have to deal with this today, but also tomorrow as well.
In the Wednesday afternoon update, we’ll discuss the category system, (the 1-5 scale, what it will look like on a map, and what it means for you.) and I want to discuss more about tomorrow as well.
Make sure you’re on the lookout for that.