The National Weather Service updated its prediction this past weekend for when Suicide Basin will become full.
According to the NWS, it will fill by Aug. 8. The previous prediction for when the basin would be full was Aug. 14.
The prediction was updated on July 12.
Over the past two years, the filling of the basin has coincided with the basin releasing its water in devastating glacial outburst flooding.
Aaron Jacobs is the senior service hydrologist with the Juneau National Weather Service office. He said that during the past two major flood events, the flooding started four to six days after the basin had filled.
The USGS monitors the water depth of Suicide Basin with webcams and a laser. The depth of Mendenhall Lake is also monitored. According to the University of Alaska Southeast’s glacial flood dashboard, when the basin starts to drain, the water level in the lake can rise quickly.
Jacobs said the peak of flooding normally happens 48 hours after they detect a rise in water levels.
The basin does not need to fill completely for a glacial outburst flood to occur, he said. According the NWS Suicide Basin monitoring page, Mendenhall Lake would peak at over 14 feet if the the entire basin drained right now.
The peak in 2024 was 16 feet.
Jacob said the change in the prediction for when the basin will fill was based on heavy rain last week, which increased the rate at which the basin was filling. He said the rate has gone down, but it might increase in the coming weeks because of warmer weather.
As the rate charges, the prediction of when the basin will be full can change, he said.
He said they will keep the NWS monitoring page updated weekly and with any new relevant information. More information can be found on the monitoring page at https://www.weather.gov/ajk/suicideBasin.
The University of Alaska Southeast also maintains a website with information and updates about glacial outburst flooding at https://www.juneauflood.com.
Editor’s note: This story has been corrected to reflect that the flood dashboard (juneauflood.com) is maintained by researchers at the University of Alaska Southeast and not by the City and Borough of Juneau.
