Severe thunderstorms are expected today from central and western Iowa to northeastern Kansas. These storms are likely to produce large hail, severe gusts, and a few tornadoes, with the greatest threat centered in these areas. Further south in Oklahoma and Texas, isolated storms will form posing mainly a large hail risk.

Locations:

  • Primary Risk Area: Central and western Iowa to northeastern Kansas.
  • Secondary Risk Area: Western Oklahoma to Northwest and Central Texas.

Threats:

  • Large Hail: Hail sizes may exceed 2 inches in diameter, with some sizes near baseball size, especially in the secondary risk area.
  • Severe Wind Gusts: Gusts potentially reaching 60-70 mph.
  • Tornadoes: A few tornadoes are possible in the primary risk area.

Discussion

Weather Patterns: A near-zonal pattern persists east of the Rockies, with a mid/upper-level cyclone moving slowly over the Northern Rockies. A shortwave trough currently over eastern Montana and central/southern Wyoming will move eastward, impacting the Upper Mississippi Valley tonight.

Atmospheric Dynamics:

  • Surface Features: A low is moving from northwestern South Dakota to northeastern South Dakota with a triple point potentially forming over northern Iowa or extreme southern Minnesota. A cold front extends from northeastern to south-central Kansas, curving back through the Oklahoma Panhandle into northern Colorado.
  • Moisture and Instability: Moisture streaming northward from the Southern Plains will mix with diurnal heating to steepen lapse rates significantly. MLCAPE values will range widely, with the highest expected over eastern Kansas (up to 3000 J/KG).
  • Storm Development: Thunderstorm development is anticipated this afternoon, beginning around the Siouxland area and becoming more widespread southward. Supercells are likely given the favorable shear profiles and enlarged hodographs, particularly over eastern Kansas where instability is maximized.
  • Severe Potential: The environment supports both hail and severe wind, especially as storms initially develop in supercell modes capable of producing very large hail. As storms merge or grow in scale, wind threats may become more pronounced.
  • Southern Target: A few storms are likely to form along the dryline from Northwest Oklahoma down in Texas. These storms will have weaker shear to work with than those further north, but the degree of instability suggests a hard right-turner would be capable of becoming a robust supercell with a hail threat. The degree of capping is such that it seems unlikely that a storm will maintain itself into the evening to take advantage of rapidly improving low-level shear, but if that did happen, a tornado would be possible.

Impact: The setup today indicates a significant risk of severe weather across the central to northeastern parts of Kansas up through western and central Iowa. The potential for hail, damaging winds, and a few tornadoes makes this an important day for vigilant weather monitoring and preparedness in the affected regions.

Technical Discussion

Refcmp uh001h.us c-18.

Storm development today will be pretty late, with robust storm development likely by 4-6 p.m. from Kansas to Texas. Further north, storms will form earlier and be more robust, with strong supercells possible through the 7 p.m. hour.

Hrrr_2024043013_009_area_41.11 41.53. 95.73  95.18.

In the northern target, storms will have slightly veered low-level winds to contend with, but the storm relative hodographs still suggest the shape is sufficient for tornado production today with any sustained and robust supercell. This will be especially true as the low-level winds back into the evening with increasing speeds. The thing to watch for Iowa/Kansas is storm crowding/merging outflows in the evening, which could interrupt low-level processes. Because of that, the tornado risk isn’t thought to be enhanced or significant.

Hrrr 2024043013 012 32.39--99.67.

For the southern target, to get storms you’ll need to mix the atmosphere enough that any storms would tend to be higher-based storms. These cells will be capable of large hail and damaging winds though. By evening cloud bases will begin to lower but as the sounding shows, capping is also on the increase and the hodograph size is not that great. Effective SRH values generally at or less than 75 will tend to promote multicells or weak supercells south of the Red River. If you can get a robust storm off of the dryline in Oklahoma, the shear is just a bit higher and would tend to promote supercells.