It's often called the "Forgotten Outbreak" or the "Lost Outbreak" given the magnitude of what happened just two weeks later, but the tornado outbreak of April 14-16, 2011, stood as one of the worst in years up to that point.

A powerful low-pressure system moving across the country spawned tornadoes for three consecutive days, with a focus in Oklahoma on April 14, Alabama the following day, and North Carolina on April 16.

178 tornadoes touched down throughout the southern U.S. over that three-day window, making it one of the most prolific tornado outbreaks on record.

This was North Carolina's largest tornado outbreak on record, with 31 tornadoes touching down in the state. Five of N.C.'s tornadoes were EF-3s, with eight more EF-2s.

38 people died as a direct result of the storms that week. The event was one of nine billion-dollar severe thunderstorm events to strike the country in 2011.

A generational tornado outbreak unfolded across the southern and eastern United States on April 27, 2011. The event holds the record for the most tornadoes ever recorded in 24 hours, with 247 tornadoes confirmed by survey crews through April 28.

Tornadoes ripped across portions of 18 states during the outbreak, with the brunt of the tornadoes focused on interior sections of the southeast. Alabama bore the brunt of the outbreak with 62 confirmed tornadoes striking the state April 27.

Six of the tornadoes were scale-topping EF-5s with winds of 201+ mph. These high-end tornadoes scrubbed well-built structures clean off their foundations, debarked trees, and left behind extreme scouring of dirt and asphalt from the ground.

This was one of the deadliest tornado outbreaks on record. 348 people died from the storms on April 27-28; most fatalities occurred in Alabama. One high-end, long-track EF-4 tornado that cut from Tuscaloosa to Birmingham was responsible for 65 deaths and more than 1,500 injuries.

The longevity of the tornadoes matched their ferocity. Survey crews found that the Tuscaloosa-Birmingham tornado was on the ground for more than 80 continuous miles. Some of the supercells cycled with multiple tornadoes over hundreds of miles.

Forecasters predicted this tornado outbreak well in advance, giving days of notice that April 27 would be a red-letter weather day that required significant attention and precautions.

Making matters worse is that the outbreak was immediately preceded by a powerful squall line with embedded tornadoes that tore across the affected areas earlier on the morning of April 27.

Many of the communities shattered by tornadoes later in the day were still reeling and without power from that morning's awful storms, a potential factor in at least some of the subsequent deaths and injuries.

One of the strongest and deadliest tornadoes ever recorded in the United States ripped through Joplin, Missouri, in the early evening hours on Sunday, May 22, 2011.

A powerful supercell entered southwestern Missouri to find an ideal environment to produce a significant tornado. The twister touched down just west of Joplin and grew more than one mile wide by the time it reached town.

The multiple-vortex tornado churned through south-central Joplin, reducing street after street of homes and businesses to unrecognizable rubble.

Survey crews assigned the tornado a scale-topping EF-5 rating based on indications of 201+ mph winds amid the rubble. Very few structures can withstand the 201+ mph winds needed to achieve EF-5 level damage. Experts used clues like an entire hospital shifting on its foundation as the basis for this tragic tornado's rating.

158 people died as a result of the immense size and scale of destruction left behind by the Joplin tornado. It was the seventh-deadliest single tornado ever recorded in the U.S., and the deadliest since the advent of modern severe weather forecasting and warning systems.