An unrelenting snowstorm in the nation's midsection killed more than a dozen people by yesterday, causing plane crashes and traffic pile-ups and deflating the fabric dome of a stadium in Minneapolis.

Authorities reported 15 dead as well as numerous injuries because of the late fall snowstorm.

Two people were killed in Kenosha County, Wis., when their car was struck by another that had gone out of control on a slippery road. The driver of the other vehicle fled on foot, police said.

A helicopter plunged into the icy Hudson River off New York City during a thunderstorm, but both men aboard were rescued by a passing motorboat.

A storm dumping up to 14 inches of snow on northern and western Michigan was blamed for the crash of a state police airplane that landed and flipped over on a slick runway late Thursday at Marquette County Airport. Five people suffered minor injuries.

The storm that blanketed most of Minnesota with 12 to 14 inches of heavy snow was responsible for the death of two teen-agers, the loss of power to 100,000 homes and the deflation of a fabric roof on the Hubert H. Humphrey Metrodome, which is still under construction.

The double-layer roof deflated Thursday night, tearing on the way down. There were no injuries reported, but damage was estimated to be more than $25,000.