There’s a significant threat of large hail today, especially across portions of Eastern Oklahoma and adjacent areas of Texas, Kansas, Arkansas, and Missouri. Hail up to baseball and softball size seems a near certainty today. Additionally a damaging winds threat and a low tornado threat will exist.

Locations

  • Southern Plains: Texas, Oklahoma, portions of Kansas
  • Lower Missouri Valley: portions of Missouri and Illinois
  • Ohio Valley: portions of Illinois, Indiana, Ohio, and Kentucky

Threats

  • The primary threat this afternoon is large to destructive hail, especially across the Southern Plains.
  • Tornadoes: The tornado risk will be very low initially, as storms will struggle with a distinct lack of low-level shear and instability in the late afternoon. By early evening, shear will increase but the overall tornado threat may be modulated by more linear storm modes and increasing capping.
  • Damaging winds, especially near and after dark as storms form into linear segments or systems.

Timing

  • This afternoon through tonight

Discussion

  • Atmospheric Setup
    • A deep upper-level trough moving across the West will drive storm development across the Plains states.
    • Strong winds at different levels of the atmosphere and a warm, moist airmass set the stage for severe storms.
  • Storm Evolution
    • Initial storms will develop along the dryline and cold front, posing a significant hail threat. These cells likely will become supercells initially, with straight hodographs favoring early storm splits and robust left-split hail producers.
    • Over time, storms will likely become more linear (forming lines and clusters), leading to a damaging winds threat.
  • Tornado Potential Increases during early evening. Early supercells will pose a non-zero tornado risk, with a warning or two being likely. If a dominant supercell can maintain itself into the evening hours, the tornado threat could become locally enhanced across Southern Oklahoma/North Texas.

Uncertainties

  • The specific timing and location of individual storms are always subject to change.
  • The distribution of severe weather may be uneven and clustered depending on how smaller-scale storm interactions play out.

Technical Discussion

Storms should initially be supercells moving off the dryline and forming along the cold front. Given the degree of forcing, shear vectors being parallel to initiating boundaries/cell orientation, and the likelihood of copious left splits early, we may end up with a linear complex rather quickly, within an hour or two of storm development. The Red River Valley will be a notable exception to that, with supercells likely throughout the entire event.
At 7 p.m., storms will be more linear in nature everywhere but southern Oklahoma or northern Texas. Here, the tornado threat could become locally enhanced into the early nighttime hours if a supercell is able to maintain a dominant mode.
The threat will persist into the 9 p.m. hour with storm intensity on a gradual downward trend.
I can’t stress enough how significant the large hail threat is initially. This environment is one that you might find in a textbook for giant hail. Not everyone who gets a storm will get giant hail, but some people are going to see massive hailstones falling today. You have time now to take actions to protect your property. The effective SRH values generally at or below 140 m2/s2 don’t signal a robust tornado threat early on.
By 7 p.m. the low-level shear will become more conducive for tornadoes, but the capping may be on the increase with a large LCL/LFC separation evident on soundings. This is leading to meager 3CAPE values on various model skew-Ts. With storm mode becoming more linear and capping increasing, this may help keep the tornado threat in check near and after sunset. But a dominant supercell could pose a locally enhanced tornado threat if it can manage to maintain a robust low-level mesocyclone during this time period.