Wednesday's predicted snowfall of 6 to 14 inches in the Seattle area could be the heaviest in decades.

UPDATES: The forecast has changed since this story was published 9:17 p.m. Monday. We are blogging about today’s weather system in the Weather Beat blog. Go to this link for latest updates on the snow forecast, school closures, road conditions and all other things weather related.

ORIGINAL STORY: The Puget Sound area could be in for its heaviest snowfall in decades, as a daylong snowstorm Wednesday is forecast to drop 6 to 14 inches in the Seattle area, on top of several inches that fell over the weekend and into Tuesday.

“It will be snowing everywhere on Wednesday. Not showers, but heavy, widespread snowfall all day,” said Chris Burke of the National Weather Service.

If Wednesday’s snowfall hits at the high end of the forecast range, it would be the biggest single-day snowfall in Seattle since 14.9 inches fell on Jan. 27, 1969, Burke said. The area also had more than 14 inches of snow in November 1985, but it fell over two successive storms.

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A more immediate concern facing Puget Sound commuters was the cold and snow forecast early Tuesday, likely to create slick conditions on many roads and highways. Metro buses will be operating on snow routes Tuesday.

Public-school closures also are almost inevitable for the next couple of days. By 7 p.m. Monday, several districts, including Snohomish and Northshore, already had announced they would be closed Tuesday. Seattle Public Schools said it would operate on a two-hour delay.

On Monday, while snow fell on and off throughout the day, there was little accumulation and Seattle largely was spared.

Seattle Department of Transportation crews worked around the clock to remove ice from major roads. Many streets had been closed Sunday night, but most were open by early Monday.

Tuesday’s snow is expected to taper off by afternoon, with the major storm arriving after nightfall.

Wednesday’s heavy snow is expected to come to a messy, slushy conclusion. By late Wednesday or early Thursday, a warming trend is expected to change the snow to steady rain. High temperatures in the 40s are forecast.

Seattle Mayor Mike McGinn on Monday urged residents to be prepared and make sure they have the necessary supplies to deal with the severe weather. Officials recommended that people minimize travel, move their cars off the street, if possible, to help snowplows and check on neighbors, especially the vulnerable.

Even though the weekend snows were spotty, they still contributed to about 10 times the normal number of collisions on Washington’s highways, according to the State Patrol.

“The lesson is to slow down,” said Julie Startup, a spokeswoman for the Patrol. “The best way to reduce your chances of being in one of these collisions is to reduce your speed and increase that following distance so you have more time to react.”

Jack Broom: 206-464-2222