Flood updates Wednesday: Peak of 16.1-16.6 feet at about 7 a.m. Thursday still forecast

‘As we move through the day, the pace of information will increase,’ NWS Juneau meteorologist says; major flood stage may arrive by late Wednesday night

Sandbags and other flood protection are stacked along a home on View Drive on the evening of Tuesday, Aug. 11, 2026. (Jasz Garrett / Juneau Independent)

By Mark Sabbatini

Juneau Independent

This story will be updated throughout the day, with the most recent information at the top.

6:30 a.m. Wednesday

The Mendenhall River is rising at the rate forecast when the glacial lake outburst flood from Suicide Basin started Tuesday afternoon, with the river expected to crest between 16.1 and 16.6 feet at about 7 a.m. Thursday, said Andrew Park, a National Weather Service Juneau meteorologist, during a livestreamed update at 5:40 a.m. Wednesday.

"But there is a window of about 5 a.m. to 9 a.m., somewhere in there," he said.

The Mendenhall River was at 5.3 feet and rising about 0.1 feet per hour as 6 a.m., according to Suicide Basin’s monitoring website. But Park said the rate of rise is expected to increase after the river reaches minor flood stage at about 3 p.m. Wednesday.

"Then the river starts really increasing, picking up pace, going into moderate flood stage (of) 10 feet around five in the afternoon," he said. "And then late tonight (or) early Thursday morning, that's when we are going to forecast that major flood stage of 14 feet, and that's when the river really becomes a scary place and a really dangerous situation."

A graph shows the predicted level of the Mendenhall River as of about 6:30 a.m. Wednesday, Aug. 12, 2026. (National Weather Service Juneau)

The river should drop quickly after cresting, dropping below the "action" stage of eight feet by about 3 p.m. Thursday, Park said.

An evacuation advisory by the City and Borough of Juneau is in effect for flood zone areas and a Weather Service flood warning is in effect until 4:30 a.m. Friday. An emergency evacuation shelter is open at the Floyd Dryden campus at 3800 Mendenhall Loop Road.

City facilities, parks and trails along the Mendenhall River are closed Wednesday and Thursday.

An updated safety briefing by city, weather service and other officials is scheduled at 11 a.m. It will be livesteamed by KTOO. Updated information is also available at CBJ’s flood preparedness website and the Suicide Basin monitoring website.

"As we move through the day, the pace of information will increase, and as we go into tonight especially expect hourly updates as we watch this river and make sure we're not missing anything," Park said.

• Contact Mark Sabbatini at editor@juneauindependent.com or (907) 957-2306.