Reading this post actually made me finally sign up for Mountain Buzz so i can contribute and not just read anymore. That being said, feel free to ignore this rookie and the book I'm about to write. I'm actually launching on the 9th I've actually been doing a fair amount of research on what the flow for the MFS will be. When I first picked that permit up, the snow pack for that region was hovering right around 90% so I figured we'd have prime water (~5.0 feet), but since then the winter has never stopped. Now with the snow pack pushing 135%+, I'm getting a little anxious our trip may be a no go.
I'm not sure if you have a cut off water level (we do), but if you do here are the things I think you should look for and why i think you should still be optimistic:
First, though the snow pack for the Salmon is pretty big, it is actually on the lower end of what we are seeing in many parts throughout the Western US (see map link below). If those numbers were 195% like they are here in the Wasatch I'd already be canceling my permit. I'm looking for these numbers to begin coming down dramatically after May 1st (I'll be comparing the 1st with the 15th)
See map at: Basin Snow Water Content Map (numeric) (SNOTEL)
Second, May is key. During the seventies and early eighties it appears the Middle Fork quite commonly peaked in later May or early June (see link below). However, during the last 10+ years the Middle Fork has peaked in the month of May every year, with the exception of last year (a case for global warming who knows). So though things haven't started to melt yet, things are going to be entirely different just a couple of weeks I'm sure. I'm personally hoping the river is nearing or over 7' on May 20th (a good sign it will be peaking sooner than later).
see peak flows at: USGS Surface Water for Idaho: Peak Streamflow
Speaking of last year, I think you have to consider that a rare (once every three or four decades) event. It simply rained and rained everyday. I wasn't sure if I lived in Salt Lake or Seattle. The Payette even went to an all-time high for example, but it wasn't banner snow year by any means. If what happened last year took place this year, with all the snow we have in place, I would think the MFS would be running near 12' in early June. Lightning never strikes the same place twice right
So, to finally answer your question, if I had to guess I would bet the river pushes very close to the 9' mark around the last two days of May or the first two days of June. After that I would expect the river to fall off pretty quickly towards the 6' level (in a week or so). So, on June 10th I think the river will be between 5.8-6.8 feet, with 6.3 being the most likely level. Thanks for reading! And i personally hope May marks the end of my winter (although the 700+ inches have been fun) and the start my spring boating season!