Have fun!! It will be incredible. Did both those on a trip quite a few years ago now(jeez). Went white water rafting and did the scenic float and plenty of hiking. All great fun. The Grand Prismatic is insane. Took high res shots of that and Yellowstone Falls. Both are framed and hanging on the walls along with shots from Canaan etc.
"Super" is hyperbolic. Just like monstrous, Ludicrous, or 'Godzilla' Nino. Social media silliness.
Official categories for strength of Nina/Nino events are- weak, moderate, strong , and very strong.
Looks the like ocean/bay breeze boundary is losing its oomph. Those storms will probably weaken and dissipate as they did over here. Need another trigger.
Interpret it literally- there is an 80% chance you will get some rain- and a 20% chance you won't. Should you get some rain, amounts between a quarter and a half inch are possible.
Flood Watch. Over here just to my SW there is a Flash Flood Warning, but no flood watch is in effect. See the difference?
Anyway, see how things evolve this evening. It will not be widespread- almost never is in these setups- but decent chance places within the watch area will need a flash flood warning.