The Big Nehalem is being managed as a wild stream and hasn't seen hatchery plants since the early 90's.
The wild fish return later in the season.
I would look at the North Fork Nehalem this time of the season, but it will be low and clear with the current weather.
ODFW Visitor's Guide - Nehalem Hatchery
The hatchery manager usually updates the fishing report daily during the winter season. The number is at the bottom of the page.
There is access at the hatchery and across the river on the Longview Fiber property, if the gate is open to fisherman. Read the signs for any closures, better yet ask at the hatchery.