The Taku River is expected to reach flood stage early today, according to the National Weather Service.
Weather service forecasters issued a flood warning Tuesday for the river south of Juneau, saying it would reach flood stage at about 1 a.m. today.
The river is expected to crest late this morning and remain at a high flow until Thursday.
Water temperatures in the upper 30s indicate that a glacial dam released at No Lake, just across the border in British Columbia. Lake observations show that No Lake is at its fullest level in 20 years, forecaster Aaron Jacobs said.
The river, at 42.3 feet, was nearing flood stage at 4 p.m. Tuesday.
Flood stage is 43 feet. Water will flow into yards and houses along the banks at that stage, Jacobs said.
Many of the cabins along the banks are built on stilts, Jacobs said, and owners are aware of flooding that happens nearly every year on the river.
"At 44 feet, we can see flow start damaging docks, and with debris coming down big trees or ice bergs can get some water into the homes," he said.
Last year the river reached 44.28 feet, but Jacobs said that because No Lake is so full, the river could reach a record stage of 45 feet this year.
The average date for the Taku River flood is Aug. 13, according to weather service records. Over the past four years, it flooded twice in August and once each in June and July.
Cold water with high levels and strong flow created hazardous conditions on the river Tuesday.
"Expect debris in the form of ice chunks and logs to also be a hazard," the weather service said.
A flood warning means that flooding is imminent or has been reported.
Flash flooding is not expected on the Taku River. Instead, the river will rise slowly, the weather service said.