The Mendenhall River at flood levels seen after the glacial outburst flooding event on Aug 13, 2025 (Photo by Corinne Smith/Alaska Beacon)
A second glacial outburst flood is bearing down on Alaska’s capital city, barely a month after record-deep floodwater came close to overrunning temporary flood barriers.
On Monday, the National Weather Service issued a flood warning for Juneau’s Mendenhall Valley after river and lake measurements showed signs of another major release of water from Suicide Basin, an ice-locked lake typically contained by the Mendenhall Glacier.
As of Monday afternoon, the flood was expected to crest between 2 a.m. and 6 a.m. Tuesday morning, just below 12 feet.
If that holds true, it would be less severe than the record inundation that took place in August or the destructive floods that soaked hundreds of homes last year.
Nicole Ferrin, warning coordination meteorologist with the National Weather Service in Juneau said on Monday afternoon, “As of right now, we’re looking at a crest sometime Tuesday morning, between 11 and 12 feet.”
That would be enough to put water into some low-lying homes near the Mendenhall River, but most other nearby homes are protected by temporary flood barriers erected last winter.
The flood in August topped out at a record-breaking 16.65 feet, below the top of the flood barriers.
“In an abundance of caution, we are recommending that folks in the View Drive area evacuate their homes this evening or just spend the night somewhere else again,” said Ryan O’Shaughnessy, the emergency programs manager for the City and Borough of Juneau, referring to the lowest-lying homes near the river.
“These floods are dynamic. They take a lot of material and change the shape of the river and lake at each event, and our No. 1 priority is always going to be the protection of life and public safety. We really encourage people to not take any chances and folks in that area, please consider spending the night somewhere else,” he said.
The city does not plan to set up an emergency shelter, and it did not send widespread text alerts to all cellphones in the area, as it did in August.
“We do not believe that there is the same risk to life and safety,” O’Shaughnessy said.
This latest flood continues a pattern that has taken place since 2011: A large summer flood is followed by one or more smaller fall floods.
Last year, after the summer flood inundated parts of the Mendenhall Valley, a flood in October crested just below 11 feet.
This month’s flood is “pretty similar” to what happened last year, but recent heavy rain is expected to contribute to higher water.
Forecasters will update their flood predictions late Monday, Ferrin said. A website hosted by the National Weather Service has the latest information.
