The National Weather Service has issued the warning for Mendenhall Lake and the Mendenhall River until at least Thursday night.
Meteorologist Tim Steffen said water levels on both bodies were among their highest, with both more than a foot above flood stage as of late Thursday morning. He said it wasn't immediately clear how long the flooding would last because it wasn't clear how much water had been released.
The weather service said the Mendenhall Campground, along with the spur road to the popular West Glacier trail head, had been closed. Steffen said he expects a nearby spur road to be impassable by later in the day.
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