Go early. Go late. Go some other time.

That’s the word from state transportation officials bracing for major delays — particularly while a wildfire has closed a stretch of Highway 2 west of Leavenworth, blocking cross-state traffic through the Stevens Pass corridor.

“It’s going to be a mess this weekend,” said Meagan Lott, a spokeswoman for the Washington State Department of Transportation (WSDOT).

Even before the Highway 2 closure, WSDOT warned travelers of backups that could be 10 miles long on westbound Interstate 90 as traffic is cut to a single lane for a six-day repair job starting Friday evening on the bridge between Bellevue and Mercer Island.

The closure of Highway 2, Lott said, could cause a 20 percent boost in traffic on Interstate 90 over Snoqualmie Pass, meaning squeezing more cars, trucks, RVs and boat trailers into lanes that often seem maxed out on a summer weekend.

“More delays and more backups,” Lott said.

So check your route before you go out. As of Thursday evening, traffic was not permitted through Tumwater Canyon, the stretch of Highway 2 just west of Leavenworth. Traffic from the west side of the state could access Coles Corner and Lake Wenatchee, west of the closure.

On I-90, two projects near the Snoqualmie Pass summit could add to slow traffic Friday evening.

On the west side of the summit, workers will be installing solar-powered LED lights in a test to mark barriers and lines between the lanes. East of the summit, crews will be working on a project to add lanes and bridges and stabilize the slope above them. Work may proceed through the night on one or both of those jobs, but workers are expected to be clear by 9 a.m. Saturday, Lott said.

WSDOT has acknowledged that its summertime jobs impact traffic, but officials say highway crews have a large number of projects that need to be done in dry weather.

On an average day year-round, 27,000 vehicles a day cross Snoqualmie Pass. On a busy summer weekend day, that rises to 40,000 or more.

Although congestion is certain on Friday as people head out of the Seattle area, some cross-state travelers say the return will be even worse, as drivers begin to clog the westbound lanes on the pass heading home as early as noon on Sunday.

Lott said that depending on their destination, travelers may want to consider far-flung detours such as the North Cascades Highway or White Pass. Those options add miles but could reduce stress, she said. Even on those routes, however, drivers this weekend are not likely to find vast stretches of open pavement.

Jack Broom: jbroom@seattletimes.com or 206-464-2222