Originally Posted by Z.Taylor
Ive done everything on Colorado, but the grand. Ive only done Grey deso on the green.
A swift water Westwater (maybe like the terrible teens) is likely the best comparison from your stated experience. In all honesty the biggest challenges on the Middle Fork are continuous in nature which doesn't really compare to the pool drop whitewater we share in Utah.
I am sure folks with direct experience can help you more than I as I have only done it medium to low water. Even at those levels it does not compare much to other rivers I have done. At higher water you will be running some of the bigger rapids from boat scouting only as there really only are micro-eddies along the shore.
I have run many of the classic multi-day whitewater in the West but personally have stayed away from high water in Idaho for several reasons:
1) Limited experience practicing continuous class IV. Not many day runs in my neck of the woods. I have run the Grand and low water Cataract and Westwaters but they really aren't the same (pool drop vs. continuous).
2) Limited swift water rescue experience. None of my friends have any training and mine is limited to training for other certifications. I know my riggings for rescues but have not practiced the technical rope work in years.
3) Fellow boatmen without much interest in those types of objective hazard: swift, cold water in continuous Class IV terrain with potential for spring debris.
4) Many of my fellow boatmen with needed skills are in the category with concerns for cold water shock (i.e. cardiac arrest from immersion). One has actually been told by his doctor never to do that type of rafting again.
5) Most of my crew lacks dry suits and/or a desire to deal with that type of cold water in lambently cold temps (snowing and/or freezing rain is common that time of year). Getting a group with the right equipment and mentality for these conditions is paramount.
I have no desire to scare someone away from an experience they are fully capable of but you will need to inventory your personal skills and goals diligently alongside those of your boating crew. Only you will know if it fits the situation properly and if you can mitigate the risks.
Best of luck and hope you get some helpful information from this forum.