Lengthy SoCal hike, mid March. Any recommendations?

5 hours is a good radius. You could make it up to Sequoia/Kings Canyon, and there are infinite possibilities up there. Somebody recently published a “Big SEKI Loop” I think… search around, I’m sure you’ll find it.

You could always pick out a section of the PCT closer to home. But if you’re going for a few days, it’s worth the drive to get to the Sierras.

Cullen –

Our back yard is the SF Bay Area, and we don’t have any experience in the LA area.  Here are a few thoughts that might be helpful, and hopefully you’ll here from some Southern California locals.

Sierras in March is a fantastic destination for a backcountry ski trip, and there are some classic backcountry ski trips in SEKI.

The Diablo Loop in the SF Bay Area is longer than your 50-80 mile target, but you could do just a subset of it if you only have a few days.  March to May are the best months, so it fits into your timeframe.  It’s a long way from S California, too far if you just have a few days.

Take a look at the Southern California route described in this thread.

I’m not familiar with the southern district of Los Padres National Forest, but there is great hiking in the northern district, and that might be within your 5-hour drive limit.  March is a usually a great month there although there is still potential for stormy weather.  There are many options, here are two as examples:

https://backpackinglight.com/forums/topic/70783/

https://backpackinglight.com/forums/topic/39869/

quite a few snow free miles on the SoCal section of the PCT.

water may be an issue on some of it though.