If you're in Eureka and heading inland, here's some fun options:
Run up to Orick and take Bald Hills road to Hwy 96.
Hwy 96 to the Salmon River.
SAlmon river road to Forks of the salmon, then take the south fork to Cecilville, and on out to Callahan. Or jump on the North Fork and take the shorter run to Sawyers Bar and Etna.
At Callahan you're on Hwy 3. Turn North to bail out to I-5 Via Etna, Fort Jones, and Yreka, or make a loop back to hwy 96 via the Scott River Road out of Fort Jones (narrow and twisty, limited sightlines).
Or, Turn right (South) (ish). You'll very shortly have two choices, HWY 3 south over Scott Mountain and then through Trinity Center into Weaverville, where you can pick up Hwy 299 in either direction, or you can stay on Gazelle-Callahan road into Gazelle, which will let you out near I-5 North of Weed.
Any of these options leave you with more great riding choices. Dirt options multiply these significantly. Hwy 3 south from Weaverville to hwy 36 (via a short jaunt on 299) is of course a great addition to a ride like this, and once you hit 36 you have more great options-back to the coast or back out to Red Bluff (too hot for me this time of year, but some like it).
If you've never been up the Salmon River, the south fork is spectacular but narrow and twisty. The North Fork is to my taste slightly less spectacular but still narrow and twisty. There's no center line and sight lines are limited. No guardrails either. Often you need to watch for vans racing to pick up their rafters downstream on this ride but this year there seem to be fewer of these as the flows are way down from the usual.
The riding up here is spectacular and varied, and can be hot this time of year. There's just too much to even begin to scratch the surface in a finve-minute post made while watching the clock at 5:00 on Friday....