People view Mendenhall Glacier from the Mendenhall Glacier Visitors Center area Sunday in Juneau, Alaska. (Marc Lester/Anchorage Daily News via AP)

Officials on Tuesday urged residents in some parts of Juneau to evacuate ahead of what could be a record surge of flooding after rainwater and snowmelt in a huge basin dammed by Alaska’s Mendenhall Glacier started to flow downstream.

Officials in recent days have been warning people in the flood zone to be ready to evacuate. On Tuesday morning they confirmed water had started escaping the ice dam, with flooding expected late Tuesday and on Wednesday. They advised people in the city’s flood zone to leave.

The Mendenhall Glacier is about 12 miles from Juneau and is a popular tourist attraction due to its proximity to Alaska’s capital city and easy access on walking trails. Homes on the city’s outskirts are within miles of Mendenhall Lake, which sits below the glacier, and many front the Mendenhall River.

The water that’s being released in the glacial outburst is flowing into the river, putting homes that are closest to the river at risk. The National Weather Service said it expected flooding to peak at 4 p.m. local time Wednesday.

“This will be a new record, based on all of the information that we have,” Nicole Ferrin, a weather service meteorologist, told a news conference Tuesday.

Flooding from the basin has become an annual concern, and in recent years has swept away houses and swamped hundreds of homes. Government agencies installed temporary barriers this year in hopes of protecting several hundred homes in the inundation area from widespread damage.

The thinning, retreating glacier in southeast Alaska acts as a dam for Suicide Basin, which fills each spring and summer with rainwater and snowmelt. The basin itself was left behind when a smaller glacier nearby retreated.

When the water in the basin builds up enough pressure, it forces its way under or around the ice dam, entering Mendenhall Lake and eventually the Mendenhall River.