CA-4: McClintock +928

Charlie Brown (Dem) 159,703
Tom McClintock (Rep) 160,631

Is Nevada County (which was the most recent report and where Charlie Brown did quite well) going to be enough for Brown to win?

That was about 1/5 of their outstanding ballots that just came in (I assume some ballots weren't counted and some didn't have a vote for Congress), and Brown only won those 54.2%-45.8%.

The other two counties in the district where Brown currently leads (Plumas and Sierra) had fully completed processing their ballots.

On the other hand, most of the other counties in the district (except for Modoc and Lassen, which McClintock won handily and which have finished processing) also have outstanding ballots and Brown is losing in them (although not by that large of a margin)

I tend to doubt it, but it's not impossible.