The National Weather Service has issued an extreme avalanche warning for the Cascades because of a warming trend New Year's Day.

The National Weather Service has issued an extreme avalanche warning for the Cascades because of a warming trend New Year’s Day.

Road closures are likely on the mountain passes as crews clear avalanches, said Mark Moore, director of the Northwest Avalanche Center in Seattle.

“We’ve had a fragile snow pack since mid-December,” he said. “It will become extreme with the rise in the freezing level, rain and strong winds.”

The National Weather Service is tracking two possible storm fronts: a northerly track that will bring strong winds to the Seattle area, and a southerly one — the most likely track — that will bring high winds to southwest Washington and Oregon.

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“There’s a lot of uncertainty,” said Ted Buehner, with the Weather Service, adding that the latest storm will bring heavy snow in the mountains and a threat of flooding in local rivers.

In the mountains, 1 to 2 feet of snow could fall by Thursday night, and 8 more inches on Friday.

Seattle should receive some rain, likely less than an inch, Buehner said.

He noted that if the storm takes a northerly track, winds locally would be up to 60 miles per hour.

Meanwhile, city crews were out cleaning storm drains and sweeping sand from streets this week in anticipation of new storms.

Seattle has more than 70,000 storm drains and “they should all be in pretty good shape,” said Andy Ryan, a spokesman for Seattle Public Utilities.

Last week, when the Weather Service warned of potential urban flooding, the utility dispatched crews to clear debris from drains, culverts and other drainage infrastructure, Ryan said. But those problems never materialized because snow melted gradually and the area didn’t get as much rain as initially forecast.

“We had all these people out ready for a party, and nobody came,” Ryan said.

The city has cleaned up about 2 percent of the 9,000 tons of sand it dropped on Seattle streets to help with snow and ice, giving priority to areas prone to flooding.

Six sweepers have been sweeping up sand and dumping it into trucks, which take the material to a landfill in Renton for cleaning and drying for use in later road projects, according to Seattle Department of Transportation spokeswoman Marybeth Turner.

The cleanup is occurring at night, largely because there is less traffic and fewer parked cars, and because day-shift crews and equipment are being used to fill potholes, she said.

While utility workers aren’t yet overly concerned about flooding later in the week, Ryan said, the city is taking just-in-case precautions. Sixteen trucks — which Ryan described as “giant wet vacs on wheels” — have been dispatched, half to the north and half to the south of the Ship Canal.

The city also is distributing sandbags at three locations for crews and residents to use as needed. They are at:

• The north side of Meadowbrook Pond on 36th Avenue Northeast, south of Northeast 110th Street.

• Northeast 95th Street and Sandpoint Way Northeast.

• Seventh Avenue South, just north of South Cloverdale Street next to Cesar Chavez Park in South Park.

Seattle residents who have drainage or flooding problems should call the utility’s 24-hour Emergency Response Center at 206-386-1800.

Sara Jean Green: 206-515-5654 or sgreen@seattletimes.com

Seattle Times staff reporter Susan Kelleher contributed to this report.