Overnight Lightning, Morning Squall Line, and Cold Front – May 20–21, 2024

A warm front approaches eastern Nebraska on May 20, 2024, setting up a volatile stretch of severe weather. Thunderstorms begin building at sunset, leading into constant overnight lightning that flashes across the sky for hours. By dawn, a fast‑moving squall line sweeps through, followed by rapidly increasing atmospheric instability and a tornado watch as the warm sector deepens. Early afternoon storms erupt along the boundary, and the colliding squalls on camera merge into the exact supercell that later produces the Greenfield tornado after it moves into Iowa. A sharp cold front pushes through later in the day, clearing the atmosphere and revealing a calm sunrise to end the sequence. This timelapse captures the full evolution of the event — warm‑front development, lightning structure, squall line dynamics, instability build‑up, supercell genesis, and the dramatic frontal passage. Timestamps: 0:00 – Warm front approaches, clouds develop 1:45 – Thunderstorms build at sunset 3:20 – Constant overnight lightning 6:30 – Squall line at dawn 8:19 – Major atmospheric instability builds in the late morning, tornado watch 9:22 – Thunderstorms blow up in early afternoon 9:47 – Squalls collide on camera, forming the exact supercell that later produces the Greenfield tornado 10:33 – Cold front pushes through 13:12 – Sunrise and lovely day Music: Olde Salooner Blues - Midnight North ‪@MidnightNorth‬ A Trip Around the Moon - Unicorn Heads ‪@UnicornHeads‬ March of the Hares - Nathan Moore ‪@NathanMooreSongs‬ How it Began - Silent Partner Vital Whales - Unicorn Heads ‪@UnicornHeads‬ YouTube Audio Library