1:30 AM CDT | April 20, 2018
Our next weather system is moving through the Western US right now. By Friday evening, it will begin approaching the Southern High Plains. Lift ahead of this system will increase and result in the development of showers and storms. This activity will begin in the Texas Panhandle and West Texas late Friday, spreading eastward Friday night and early Saturday. For today, the Severe Risk appears marginal at best and limited to the higher terrain of West Texas.
Saturday's setup has my attention. I have mentioned over the last few days that there will be the possibility of Severe Weather. Most outlets are suggesting that the greatest threat will be heavy rain for North Central Texas on Saturday with only a low risk of Severe Weather. While nothing is set in stone, let me explain WHY I am watching Saturday's weather so closely. First, closed lows rolling through Arizona and New Mexico usually produce Severe Weather in the Southern Plains this time of year. It's more than that, however. It reminds me of past setups such as what we saw back on May 15, 2013. Now, I am NOT saying that it will be a repeat of that outbreak, but there are similarities. My main reason for referring to it is because it serves as a good example of how these setups can "sneak up" on you. It wasn't until the day began to unfold when it became really apparent that a second more intense round of storms would form. Take a look at the 500mb pattern at 7:00 PM on May 15th. Then, take a look at the Severe Weather Reports that occurred.
In the days leading up to the outbreak, the media kept stressing that widespread clouds and rain would hinder instability. Thus, they thought the risk would be very low. The SPC had a Marginal Risk up until the night before when they added a Slight Risk for western North Texas. As the day progressed, they gradually shifted the risk eastward and also bumped of the probabilities across North Central Texas. Why? Because it became more evident that enough clearing/heating would occur near the dryline for a second round behind the earlier activity. This second round developed by early evening to the west of I-35 and tracked east and southeast as another piece of energy rotated into the region. At the surface, there was a surface low in western North Texas, which aided in storm development. Compare the above graphic to this evening's NAM model. This is what it is predicting at 7:00 PM Saturday.
While earlier activity will delay destabilization, as mid-level winds become more westerly as the system pushes further into the Plains, I believe some clearing will occur closer to the triple point in western North Texas Saturday afternoon. This is most likely near/W of the I-35 corridor based on the current timing of the system. If this indeed occurs, a narrow band of instability would develop and increase the risk for a few Severe Storms. Wind fields will be supportive of organized storms, including Supercells. This is the latest outlook from the Storm Prediction Center. If you are in or near the risk area, keep an eye on your local forecast for Saturday. To reiterate, the purpose of this discussion is to explain why I believe we could see a few Supercells on Saturday. I am not saying that we will see an outbreak. What I am saying is that the risk will probably be greater than the marginal risk being advertised at this time. Check back here and on the Facebook page for updates!