Which ones ya looking for?
Unfortunately, the National Weather Service doesn't do forecasting for all gages and only the Colorado Basin River Forecast Center presents their data in such a way that I can poach and produce these detailed graphs.
Personally, my favorite and I think the easiest way to access the most commonly queried forecast hydrographs is via the following hyperlink:
I suggest clicking on both the Flow Report and Flow Report Summary.
In column 34 for most rows is the symbol "3" which will link you directly to the forecast hydrograph for that river.