Strong tornadoes, giant hail threaten Iowa to southern Great Lakes as severe storms redevelop

An enhanced risk of severe thunderstorms is forecast from eastern Iowa through southern Wisconsin, northern Illinois, and the southern Great Lakes region, with threats including large to giant hail, several tornadoes—some potentially strong—and damaging wind gusts. The highest risk is centered near a stalled frontal boundary extending from eastern Iowa into southern Wisconsin, where conditions such as low-level wind shear and atmospheric instability are expected to overlap. Forecasters anticipate that storms will rapidly organize into supercells capable of producing all severe hazards from late afternoon through overnight. The Storm Prediction Center (SPC) highlights that moisture advection combined with steep mid-level lapse rates will support mixed-layer CAPE values at or above 2,500 J/kg across parts of Iowa and the Iowa–Wisconsin–Illinois border region. This environment favors intense supercell development, with the tornado threat particularly elevated near the frontal boundary due to enhanced storm-relative helicity. As the evening progresses, storms are expected to merge into a severe cluster, driven by a strengthening low-level jet, which will expand the damaging wind threat eastward toward the southern Great Lakes. Tornado risks may persist if storms develop ahead of the main line during boundary layer recovery. Farther south, scattered severe thunderstorms are also anticipated from eastern Kansas into Oklahoma and western north Texas, where a very unstable air mass with 2,500–3,000 J/kg MLCAPE and favorable wind profiles could support supercells capable of producing large to giant hail and possibly tornadoes. This severe weather threat follows an outbreak on April 13 that produced at least 14 tornado reports across Kansas, Minnesota, Iowa, and Wisconsin, with the most significant damage near Ottawa, Kansas, including structural damage and power outages. No fatalities have been confirmed, but storm surveys are ongoing. The current severe weather pattern marks the beginning of a multi-day event affecting the central United States. The Weather Prediction Center warns of repeated rounds of severe thunderstorms and heavy rain through April 16, driven by multiple low-pressure waves along the frontal boundary. This increases the risk of localized flash flooding in affected areas, underscoring the need for continued vigilance as the severe weather threat persists across the southern and central Plains, Upper Midwest, and Great Lakes regions.