Check out those freeway signs as you head south throughout the Bay Area and you may very well see a warning about I-405 in Los Angeles.
Why should you care?
Caltrans is well aware that on weekends many of us make visits to or take visitors from the Southland. This applies to drivers, as well as those flying into and out of LAX as well.
"The 405", an integral, major freeway for Los Angeles, will be closed starting as early as 7pm on Friday, thru 6am Monday, to continue work on a new HOV lane (among other things). I've got a link to the full project details below but here are some bullet points...
Going to Magic Mountain?: You're fine.
Going to Disneyland?: You will probably take I-5 all the way there. Your route will be open, but you'll see more traffic due to the reroutes.
Going to Universal Studios, UCLA, Santa Monica or Long Beach (for example)?: You need to really focus on the reroute. Your plans will definitely be affected, probably in a painful way.
Not worried 'cuz you're flying to LAX?: Um, worry. This will affect your routes into and out of that area as well in a most major way. The 405 is pretty much the road in and out of LAX. Or it was, at least.
Disclaimer: I specifically shouted out UCLA because I am an alum. I lived in SoCal for a decade and much of that time was spent, stopped, in traffic, on the 405.