In early December a storm hit the metro, dropping over 17 inches of snow. Usually that's not a problem for the Hubert H. Humphrey Metrodome's air-supported roof, which weighs about 580,000 pounds and reaches 16 stories at its highest point. The roof is made of two layers: the outer of Teflon-coated fiberglass, and the inner a proprietary acoustical fabric. The dead air space between layers is designed to insulate the roof, and in winter warm air is blown into it to help melt snow accumulating on the top. To prevent roof tears, workers also climb on the roof and use steam and high-powered hot-water hoses to melt snow. However, strong winds during that December blizzard made it unsafe for the snow removal crew to work. The roof began to sag. On a Saturday night, a Fox Sports crew setting up for the Sunday night football game noticed water leaking from the roof and kept their cameras on all night, capturing an eerie time-lapse video. The cameras showed first a rapid leak, followed by a steady stream of snow, and finally, early the next morning, the catastrophic collapse of three of the roof panels, sending an enormous avalanche of snow plummeting to the stadium floor. The amazing video went viral within hours.