Here is some useful technical information on the South Fork from Bryce Oldenmeyer of the Henry’s Fork Foundation.
Flow update: In response to cooling temperatures and decreased inflow, discharge from Palisades Dam was decreased 2,400 cfs this (Friday, 6/21) afternoon. Current outflow from Palisades Dam is 11,400 cfs. Flows are expected to stay around this level for the next 7 to 10 days.
Snow and reservoir overview
Average temperatures the last seven days have melted most of the snow at sites above Palisades Reservoir. Out of the eighteen SNOTEL sites above Palisades Reservoir, Togwotee Pass (elevation 9580 ft) and Two Ocean Plateau (elevation 9240 ft) are the only SNOTEL sites with snow. Togwotee Pass has 8.1 inches SWE (92% of median for the date; 32% of peak) and Two Oceans Plateau has 7.8 inches of SWE (66% of median for the date; 26% of peak SWE). Cooler temperatures are forecast for the next 3-4 days and runoff is anticipated to slow over the weekend. Even after temperatures are expected to return to average next week, it is likely that runoff will continue to decline as the remaining snow proceeds to melt.
The Upper Snake River system is currently 96% of capacity and expected to fill by the end of the month. Palisades Reservoir is 95% full (1,139,623 ac-ft of 1,200,000 ac-ft) and Jackson Lake is 97% full (822,279 ac-ft of 847,000 ac-ft).
With respect to fly-fishing, giant stoneflies are beginning to emerge along the river below Lorenzo. With warming weather they will soon advance up the river and become numerous enough to interest resident trout.