Severe weather will be possible today from southern South Dakota to Texas. Storm coverage will be highest in the northern and southern ends of the risk area, with the middle portions having few or no storms before sunset. After dark, lift increases, and storms should become more numerous across the risk area. A couple of tornadoes, large hail, and damaging winds are possible.

Locations:

  • An enhanced risk of severe weather spans from SW South Dakota into Western Kansas
  • Western Oklahoma and Northwest Texas

Threats:

  • Large hail.
  • Damaging winds.
  • A couple of tornadoes.

Timing:

  • This afternoon into the overnight hours.

Discussion

Deepening upper-level low driving storms: A strengthening low-pressure system over the Central Plains creates an environment ripe for severe weather.

  • Storms will form across Nebraska and South Dakota in the afternoon, along and north of a warm front.
  • Further south, storm coverage will be more sparse in Kansas and Oklahoma.
  • There should be another localized concentrated area of supercell development along and just ahead of the dryline in NW Texas.

Supercells are the most likely storm mode before dark: Strong wind shear and moderate instability will lead to an environment favorable for the formation of supercell thunderstorms.

Cap Strength Concerns: A strong cap will exist across the region today.

  • The extent of dry air west of the dryline will cause issues for dryline convection today, especially north of the Red River and South of Nebraska.
  • Storms are very likely to form in NW Texas off of the dryline, but convective inhibition really only erodes in a narrow zone here. So robust supercells may form and die all before sunset.
  • Further north, upper dynamics will help drive storm development a bit more in Nebraska, but capping concerns will remain.

Tornado threat window: The greatest risk of tornadoes will be with any sustained, surface-based, and strong supercells in the evening hours, roughly in the hours around sunset.

Overnight storms: Storms will form throughout the night with a continued risk of large hail and perhaps a tornado across Kansas and Nebraska. Storm coverage further south overnight is more of a mystery and uncertain.

Technical Storm Chase Discussion

500mb mean.cp.f01200.

A powerful storm system will emerge east onto the Plains late this afternoon and overnight, increasing upper lift.

850mb mean.cp.f01200.

In response to the deepening surface cyclone which is in turn responding to the emerging storm system, low-level winds will increase markedly into the evening across the Plains. The 850s do tend to weaken dramatically south of I-40 in Oklahoma and into Texas. They are also relatively weak in the afternoon hours.

Ref1km 004hmax pb40.cp.f01200-2.

By early this evening, storms will likely be ongoing across NW Texas, perhaps Western Oklahoma and up in Nebraska and South Dakota. Models this morning came in with a dry signal on the dryline from NW Oklahoma to Nebraska. Given the late ejecting wave, strong capping, and diffuse dryline until late in the day this does make some sense. Very dry air on the west side of the dryline may tend to mix into updrafts and cause problems as well. This could be a situation where robust towers go up, then thin out unexpectedly, with thin and puny LPs off of the dryline. If a storm can go up and thrive though, the environment is capable of higher-end severe weather.

Srh01 mean.cp.f01300.

0-1km SRH over 100 will support low-level mesocyclones in the evening with any storm that can maintain surface-based characteristics. Capping will be on the increase at/after sunset so the window seems more narrow for supercell storms to produce tornadoes. Even earlier model runs that produced storms tend to kill the supercells just after sunset. This is a day where a lot of things are going to have to go right for a storm to form and then again for a storm to be able to produce tornadoes. It’s not impossible, just a lower chance than you might otherwise expect.