11:21 PM: The State Patrol and other agencies are dealing with a deadly one-vehicle crash at the Cloverdale overpass where 509/99 meet – avoid the area. The crash brought down a big sign – see the WSP-tweeted photo above – and Trooper Rick Johnson says that’ll mean a long closure on the NB side. More as we get it.

11:39 PM: Thanks to the reader who texted this wider view:

A nearby resident says the driver hit the pole at high speed. [map]

12:49 AM: Still closed.

7:30 AM: As noted elsewhere, NB is still closed as crews deal with the sign. SB reopened overnight. Meantime, WSP’s media update says the driver was a 17-year-old Seattle resident.

UPDATE: The 99/509 crash scene has reopened as of 8:33 am.

2:26 PM: Seattle Public Schools has confirmed what was first reported in comments below – that the victim was a West Seattle High School student. Here’s the letter WSHS principal Brian Vance has just sent to families: