Then Turn Right at the Taxidermy Shop on the Corner

Well this is a new one for  me.

Good to know, given how close we live to Mount St. Helens. 

Problem is, in an effort to be fully prepared should she blow, I tried to follow the Eatonville volcano evacuation route for a little ways, but after this particular sign...nothing.  No  more signs.   There's a big arrow on this sign pointing in the direction I'm supposed to go, but after that, what?  Which street, twist, turn or general fork in the road past this sign is the right way to flee the steaming ash plumes and molten lava? 

I need a more detailed map!