Severe weather risks have been outlined for both Thursday and Friday on the Southern Plains, but each day has a lot of caveats to them at this range. The high-end potential for each day would be supercells with a threat of tornadoes, but there are signs that we could be heading for a washout and a quickly surging cold front instead. Let’s dive in.
As an upper-low approaches from the west, moisture will be drawn up into the Southern Plains throughout the day on Thursday. A moistening airmass from a dry airmass through the day is not an impossible situation to get storms on a dryline, but it usually requires a bit of extra upper support in the form of an upper wave to make that possible (see: Last week’s severe event).
As we move into Thursday afternoon, most models are hanging the main upper level energy well west of the dryline. While this won’t entirely preclude storm formation in the late afternoon, it certainly doesn’t help.
The GFS in particular is *trying* to produce some precipitation along the dryline. But it seems somewhat dubious.
The dryline should set up somewhere in the Texas Panhandle on Thursday. The surface winds ahead of it will need to back (be more out of the east) to maximize convergence. But lots of convergence is usually not enough to create storms on the dryline, usually you do need a bit of upper support to get updrafts over that last hump.
Soundings from Thursday show a pretty favorable environment for Supercells across the Panhandles if a storm can go. There is quite a separation of the LCL and LFC still, which means there is still some work to be done in the atmosphere to make it fully conducive to storm development.
Overall: Thursday seems like a day of transition on the Southern Plains with the environment rapidly moistening with an approaching upper low. If you do get storms, I think they will be at/after dark and probably rooted above the surface. This might mean some large hail will be possible in the region as upper forcing arrives in earnest. If storms can form before the sun sets, then an actual robust tornado threat may develop over the Panhandles into the early evening.
Friday is a day I could see getting a pretty big risk assigned to it from the Storm Prediction Center because the environment likely will have a lot of things you look for from big severe weather days. However, I think most signs are pointing to this day being an absolute mess of a day with heavy rain being the biggest story.
The first place I want to start is out ahead of the front/dryline in the warm sector. While this can change, there is a pretty consistent signal developing across models in developing a thick layer of low clouds on Friday in the warm sector. The degree of upper forcing means this will not preclude storm development, but it will tend to limit low level instability and total instability if it comes to pass.
By Friday afternoon, a front will be on the move across Oklahoma and Texas, with it merging with a dryline as it zippers to the south. This will be a big source of surface convergence through the day and will likely lead to a line of storms given the orientation of the front in conjunction with the 0-6km shear vectors.
Upper forcing will be plentiful and increasing through the day on Friday. It is likely a lead wave will eject sometime during the overnight hours, leading to widespread elevated storms across Oklahoma with large hail possible. The number of storms will only increase through the day as upper forcing increases.
What we will need to watch for are small breaks in clouds that increase the 0-3km instability on Friday. Despite what I think is going to be a very messy storm mode evolution, the overall wind shear environment is somewhat favorable for supercells and tornadoes. If you can destabilize the low levels and keep cellular storm modes, tornadoes will absolutely be possible on Friday across Oklahoma/Texas.
With that said, the most likely scenario at this time is for Friday to have storms ongoing most of the day and increasing in number and intensity into the afternoon, eventually forming into a line along the advancing front. Severe weather does seem pretty likely, but the overall tornado threat will depend on a few factors that aren’t entirely clear at this range.
Friday could go either way. I think the thing to watch for on Friday will be the progress of any overnight convection on Thursday and then if you can get any sun through the morning into the afternoon on Friday. In a lot of ways, this feels like a storm event in the Southeast where you really need cloud breaks and then it would be game on even with messy storm modes. We’ll post additional updates on our latest thinking in the coming days.
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