This story has been updated to include new information.
City and Borough of Juneau Docks and Harbors issued a warning for severe weather, asking boat owners to make sure their vessels are secure and prepared for heavy rainfall.
The warning comes as the National Weather Service issued a flood advisory for the Juneau area extending to Friday night, upgraded from a watch on Thursday afternoon.
“[We’re worried about] mainly heavy rains. Check your bilge pumps,” said Harbormaster Matt Creswell in a phone interview. “The bulk of it is tomorrow, I believe.”
Heavy rain was expected to begin Thursday evening and persist into Friday afternoon, said Caleb Cravens, a National Weather Service with the Juneau office.
“The heaviest rain for our area isn’t expected to arrive till late tonight, tomorrow [Friday] morning,” Cravens said in a phone interview on Thursday. “We’re monitoring right now the potential to upgrade to an advisory. The main concern here is going to be our rivers. The Montana, Jordan Creek, the Mendenhall.”
The heavy precipitation is being caused by the “atmospheric river” phenomenon, which is moving south from the northern panhandle due to pressure shifts, Cravens said.
“The forecast is on track to see a shift south in the atmospheric river to the central panhandle,” Cravens said. “Imagine it being like a water hose funnelling moisture into the central panhandle.”
The rain is predicted to taper off beginning Friday afternoon, Cravens said, though some precipitation will still be falling.
“We will start seeing a diminishing trend on Saturday. For the Juneau area, we’re looking at heaviest precip starting tonight lasting through tomorrow afternoon. By tomorrow afternoon we’ll see a noticeable decrease in precip. It’ll become what we call showers, and decrease further,” Cravens said. “We do have another round of rain on Saturday, but it won’t be nearly as heavy or organized.”
• Contact reporter Michael S. Lockett at 757-621-1197 or mlockett@juneauempire.com.