That's a bummer. And this won't sound good for my chances, but I've never been on Mt Si. It's too crowded, and it's too close; all the hiking I've done along the I-90 corridor has been further out, on trails surrounded by mountains, instead of at the very edge of the range. So it'll be good to start going now, and learn the trail. But I don't have crampons (yet).
I did the Denny Creek Trail on Sunday, up to Keekwulee Falls. It was a six mile round trip hike, because the road is closed a mile from the trailhead. Mostly I was able to walk on top of the snow other people have already beaten down ( "Cascade Concrete" ) but every now and then I'd break through. That's only ~3,200 feet.