Welp, here's my update: I crawled under the dash Saturday afternoon when it was warm (close to 40F) and started playing around with the rubber steering shaft boot on the firewall, squishing it around and just manipulating it to try and redistribute any lube that was in there. The steering wheel wasn't making the sound at that time, presumably because it was much warmer than it's been.
Since that time, the weather has been down in the teens and single digits again, and so far, NO NOISE. I'm probably jinxing myself with this post, but so far, so good. Fingers crossed it stays this way.
Thanks to Ultramaroon for the suggestion. I would've bet money against the boot being the issue, but I guess that's why I'm not a betting man.
