Good afternoon,
Let me begin by saying although we are watching Saturday and Sunday for chases due to the threat of severe weather, Monday by far looks to be the most ominous/significant at this point. Here is the day 4-8 convective outlook issued by the Storm Prediction Center.

This outlook works differently then the day 1 – 3 outlooks. In order to be highlighted on the graphic above, the risk must be great enough to support a 30% probability of severe weather within 25 miles of a given point. Thus, if you’re in any of the outlook areas above, you have the highlighted for the potential of at least a 30% chance of severe weather within your location. At this point, day 4 (Sunday) and day 5 (Monday) are our primary interest and have been highlighted, with a unusually large area highlighted for Monday. As we look at the model data, you should be able to see why.

Since we’re still five days out, a lot of this will most likely chance somewhat, but lets start looking at model data coming off the 12Z GFS. We’re going to start off at the mid to upper levels, so lets take a look at 500 MB (around 18,000 feet) at Monday Evening.

The first thing I see on this output (which has been fairly consistent) is the deep trough over Texas, associated with a strong piece of energy over the region. Winds at 500 MB look to be over 60 knots over most of the warm sector with this solution. One thing you would want to see generally is a more veered flow aloft, meaning the winds slightly more southwest, like over West Texas. This is a moot point this far out. This map is favorable for mid and upper level organization of convection.

As we lower down to 850 MB (roughly 5,000 feet off the ground) you can see the map is lit up like a Christmas tree. A very strong low level jet is centered from East Texas all the way over into the SE US. The peak value I see on this map is 65 knots, which is extremely high. These values are common with strong low pressure systems in the wintertime, such as a nor’easter, and winter time severe weather events where you have marginal instability. As we continue to look into this setup, you’ll see that we’re going to have a volatile combination of shear and instability present.

This system is definitely not your winter-type system. For the moment, the GFS has 60 degree dewpoints making it as far north as I-80 in the Chicago area, with 65-70F dewpoints making it up to central Illinois and Indiana. Whenever you get deep moisture that far north in early spring, you have the potential to create a nasty severe weather event should the right system come into play. Unfortunately for residents living in this large area, a very strong system is coming in and will tap this moisture.

 

When you begin to look at these instability graphics, I want you to keep in mind the 850 MB graphic above as I start talking about this. This run of the GFS has over 1,000 J/KG of surface based instability up into central IL, with a very large warm sector (area of instability) from the I-35 corridor in Texas eastward to Alabama. When you line up the very strong low level jet at 850 MB combined with this instability, you have the potential to create a very significant severe weather event, with all modes of severe weather possible. In fact, these are the types of setups that can create some of your more prolific events. I’m not saying that’s going to happen, but the possibility that Monday could end up with significant severe weather is definitely a possibility. What is also concerning is the amount of instability present. This is a large area with instability, even up north closer to Chicago. Folks living in Texas, Oklahoma, Missouri, Arkansas, Tennessee, Louisiana,  Mississippi, Alabama, Kentucky, Indiana (just to name a few states) should be getting ready for a very active severe weather day with the possibility of all modes of severe weather. While we’re still several days out, confidence is increasing that this will be a major day. Timing is still in question, but folks should be keeping a close eye on this as it has the potential to bring major implications to the affected areas. This graphic only shows surface-based instability. North of the ‘clear’ areas may have some elevated instability, which would allow storms to become stronger with mainly a hail threat. Your local weather service offices will be able to provide each of you more information on your specific threats.

 

The reason I’m becoming concerned about the possibility of a widespread event is the lack of any convective inhibition over many areas. For the past several weeks we have been dealing with cap issues that have prevented convection from really getting going. Last week that happened three times to us. Based off the current GFS, this would not be a problem, with convection underway by Monday afternoon across many areas (see graphic below). For a chase standpoint, it is simply way too soon to even start thinking about where we may end up on Monday, and I do plan on chasing Monday. I’ve already re-arranged my work schedule so I’ll be able to do that. We’re also too far out to talk about specific threats, but all modes of severe weather are possible (if not likely).

This graphic is indicative not where precipitation may be underway, but more of an indication of how weak the cap is and how widespread severe weather may be. It’s also interesting to note that even though there is precipitation being shown on the models, how high the instability is being kept, even though precipitation would normally lower instability amounts. This could be a volatile situation for sure. Stay tuned as we get closer to Monday as keep watching this system. We’ll be providing updates on the blog, facebook, and twitter with the latest regarding the upcoming severe weather chances. While we can’t answer everyones questions, we try. If you have any questions or comments about this upcoming setup, feel free to ask us on facebook or post a comment below. Also, be sure to check out our new live streaming page we brought online last night! This is the system we’ll be using this weekend into early next week as we’re out chasing.

Thanks for stopping by!

- David