I have done this 30-40 times. Up canyon winds blow in the afternoon(adiabatic) due to heating of the surrounding mesas heating before the canyon bottom. Storms are a different horse.My first flip was @ surprise.Due to wind. WE had layed over @ Spanish for 3 days hiking and waiting for the wind to subside. It didn't.I could not make my line @ the pourover and kept getting blown back into the pool.50 mph, 50 degrees air and water.The hole was surging due to the hydraulics and the wind pushing up a haystack, then subsiding as the flow over powered the wind up to 12'. As we finally entered the wave subsided as we crested and the wind caught the boat(14.5' 2500lbs) and flipped it sideways in the air.No hydraulics involved.
I've run Cat from 120,000 '83 to 5000 in the fall.With a motor @ high lake level and 120' low. Your run will likely be in the 30-50,000 range which will get your attention in the Big Drops and hopefully before.
A motor is noisy, heavy,(gas and iron) and is only usefull for egress if the lake is high, which it won't be...likely 3650 or so.Current will run into narrow canyon.You'll have all that weight in the Big Drops for little gain.This is a wilderness serious whitewater trip.
Not an amusement park ride. The confluence is always difficult due to the mixing of currents.The wind does not always blow there, anymore than the Riparian has fish in his bathtub... The flatwater in stillwater/lab can be just as difficult if up canyon winds hit.
Buck up and be a man. Mile long, Ben Hur, Little Niagra and Satans Gut should be your focus cus it will be rippin'.
And try to be green instead of a puss.
And cold spray??? Gee, maybe a low water trip on the San Juan won't get your thong chilled.