Suicide Basin above Mendenhall Lake has begun the expected glacial release and water is moving quickly into Mendenhall Lake and River.

Residents in Alaska have been warned to evacuate as snowmelt from the Mendenhall Glacier, which is about 12 miles from Juneau and is a popular tourist attraction, and heavy rains converge to threaten "record" flooding this week.

This year, a giant wall of reinforced sandbags erected with the help of the U.S. Army Corps of Engineers held back the worst of the flooding in Juneau, to residents' great relief.

Hood boarded a helicopter to investigate. Flying over the glaciers at the head of the Mendenhall River, he saw collapsed ice and stranded icebergs in a basin between the Mendenhall Glacier and one of its smaller tributaries, Suicide Glacier. That indicated water had just drained as a glacial dam released and caused the flood.

An overflowing glacial lake caused a surge in the Mendenhall River on Wednesday, prompting flood alerts and evacuations in Juneau.

The all clear has been given and residents have been allowed to return to their homes in Alaska’s capital of Juneau after a glacial lake outburst sent debris-filled water rushing down the Mendenhall River on Tuesday night and Wednesday morning.

A "glacial outburst" threatens major flooding in Alaska's capital city as a glacial lake flood phenomenon inundates the Mendenhall River.

Each summer in the mountains above Juneau, Alaska, meltwater from the massive Mendenhall Glacier flows into mountain lakes and into the Mendenhall River, which runs through town. Since 2011, scientists and local officials have kept a close eye on one lake in particular: Suicide Basin,