That’s according to Deborra, who has a good view of it from downtown. There was construction work south of the West Seattle exit, but it was supposed to be done by 3:30, so not entirely sure that’s it – just know that heading southbound on 99 will take you longer, if you’re leaving any time soon. 5:35 PM UPDATE: SDOT sends this advisory – it IS related to the road work:

SDOT is working to address traffic backups on southbound Highway 99 this afternoon.

A contractor making emergency repairs on East Marginal Way South (Highway 99) had his crews off the street before 3:30 p.m. as required by his city permit; however, two traffic lanes were left closed to allow pavement to cure, resulting in traffic backups through downtown Seattle.

One lane was opened at 5 p.m., and the third lane is to be opened before 6 p.m.