Traffic is likely to be a nightmare this weekend, with construction closures on Aurora Avenue North, Mercer Street and South Spokane Street.

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Just when it’s safe to drive a convertible in Seattle, work crews will exploit the pleasant summer weather to make progress on not one, but three big projects.

The most unusual closure will be at Aurora Avenue North and North 85th Street, causing detours that start up to two miles away. Other closures, of a more familiar type, are scheduled at Mercer Street in the South Lake Union area, and westbound South Spokane Street from the I-5 offramps to Highway 99.

On average, 140,000 vehicles per weekend pass these spots. Sunny skies tend to attract extra crosstown drivers, but they’ll need time and a solid plan if they hope to meet the Seafair Pirates at Alki Beach on Saturday.

Usually the city manages to avoid simultaneous, big closures the same weekend. Not this time.

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They’re needed to keep the city’s paving contractors from falling behind schedule in Seattle’s limited dry season, says Lorelei Williams, capital project manager for the Seattle Department of Transportation.

And certain weekends are off-limits because of major events such as the Bite of Seattle July 20-22, Hempfest Aug. 17-19 or Bumbershoot Sept. 1-3. But there will be a Sounders FC game on Saturday attracting 34,000 fans, a Storm basketball game Sunday attracting 5,000 fans, and smaller events in several neighborhoods. The city urges people to walk, bike or ride transit, including the West Seattle Water Taxi.

The three sites are:

Aurora Avenue North: New road deck and stormwater pipes are being installed. Southbound lanes will be closed at North 105th Street in all lanes — a full mile before the job site. The official detours are to Northwest Holman Road through Ballard, or to enter Interstate 5 at Northgate.

Northbound lanes will be blocked even farther out — two miles away, at the exit to Green Lake Way North. Detour routes include North 50th Street to I-5.

Crossing traffic will be narrowed to one westbound lane on 85th through the intersection.

Road closures are from 10 p.m. Friday to 6 a.m. Monday.

A city website says wet weather delayed work that was planned for late June, but Williams said there might have been a shutdown this weekend regardless. Three more weekend closures are expected, said Williams.

The $16.5 million project, to resurface crumbling blacktop on 85th from Crown Hill to I-5, is funded mainly by property taxes through the 2006 Bridging the Gap levy.

Mercer Street: The future eastbound lanes are almost done, so crews are ready to pour concrete this weekend at the entrances to I-5 ramps, and perform electrical and signal work. The ramps will close, as well as the nearby onramp from University Street to northbound I-5. During past Mercer closures, nearby Denny Way has degenerated into stop-and-go traffic.

Road closures are from 11 p.m. Friday to 5 a.m. Monday.

The $164 million Mercer East project for two-way traffic is to begin in September, followed by work on Fairview this fall and a rebuild of Valley Street next year.

Spokane Street widening: Workers will pour concrete to unite the new westbound deck with the old deck carrying eastbound cars, and install the last stretch of median barrier. The I-5 exits to the West Seattle Bridge via Spokane will close from 10 p.m. Friday to 5 a.m. Monday.

The important point is to use Highway 99 to reach the West Seattle Bridge from the city center, if possible. The usual detours through Sodo to the low bridge, or via Highway 599 to West Marginal Way Southwest, are available. The $168 million project is to be finished in September, two months late.

In hindsight, this might have been a good weekend to declare a car-free “Summer Streets” day at Alki.

Williams says it will still be possible to cross the city, because the three jobsites are spread apart. She suggests that travelers check the SDOT website at

Mike Lindblom: 206-515-5631 or On Twitter @mikelindblom.

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