Heavy precipitation and fluctuating temperatures is likely to turn a lot of Juneau’s snow to ice overnight, leading to hazardous conditions for drivers and homeowners, according to the National Weather Service.

The Juneau area received reports of 4-6 inches of snow overnight, said NWS Meteorologist Edward Liske, but Tuesday morning temperatures at Juneau International Airport were above freezing meaning that snow was starting to melt and gain water weight.

“That’s a heavier snow load on your roof,” Liske said in a phone interview. “That snow on your roof is absorbing all the water that’s coming down from the sky.”

By mid-day precipitation changed to rain in parts of Juneau, but Liske said temperatures likely wouldn’t get warm enough to fully melt the snow. Temperatures were expected to drop overnight, which could turn much of that wet snow into ice, Liske said. According to Liske, some parts of the Mendenhall Valley have accumulated up to 20 inches of snow depth on the ground, and many homes have several inches of snow accumulation.

More snow is expected Wednesday, Liske said, but temperatures look to be rising later in the week with more rain mixing with the snow by Friday.

“The coldest temperature I see is not until Sunday night,” Liske said, which would be in the low 20s,” not enough, he said, to create safe conditions for walking on iced-over bodies of water like lakes.

The Alaska Department of Transportation and Public Facilities is responsible for snow removal on several of Juneau’s major thoroughfares such as Egan Drive while the City and Borough of Juneau has its own schedule for city streets. A map showing the city’s priority streets for snow plowing is available from Juneau’s Public Works and Engineering Department.

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Refreezing overnight could create black ice on the roads, Liske said, and snow on roads has been compacted into ice already.

Juneau Police Department has already responded to reports of crashes and disabled vehicles.

Since Sunday, police received four reports of vehicle crashes or vehicles “in the ditch,” said Erann Kalwara, public safety manager for JPD, in an email. Additionally, JPD received two reports of disabled vehicles, but Kalwara said it is unknown if the disabled vehicles were related to the weather.

“It is helpful when folks let us know their intentions with their vehicles and provide a good call back number,” Kalwara said. “If a vehicle is left on or near the roadway, officers evaluate the position of the vehicle and time of day to help determine if an immediate impound is necessary. It is much more convenient and cost effective for vehicle owners and operators to arrange a tow truck privately.

“If they are blocking traffic, please call JPD. If they want a case number, the incident may be reported on line.”

The Juneau Docks and Harbors department asked boat owners to check on their vessels and remove any excess snow if necessary. Heavy snow on boats and cause them to sink, which causes a number of issues for the harbor, according to harbormaster Matt Creswell.

There were several days of light, fluffy snow, Creswell said, but when it starts to rain that snow becomes, “basically a big sponge” before potentially turning into a block of ice.

“If you have a vessel in the harbor please come down and check on it,” Creswell said. “It’s very expensive once a boat sinks.”

Creswell said harbor staff have been working to remove snow from parking lots, ramps and other public portions of the harbor, but is still suggesting people wear some kind of ice cleat when walking on docks. As conditions become increasingly icy and slippery, Creswell suggested personal flotation devices as well.

“December is not a time you want to go in the water in Juneau,” Creswell said.

• Contact reporter Peter Segall at psegall@juneauempire.com. Follow him on Twitter at @SegallJnuEmpire.