Skyrise-
The current forecast method for Snohomish (and other "S" river chum) is fry based. A regression is used based on the fry abundance on various Sound beaches. As such the driver for the forecast is not how many redds there may have been but rather how well the redds produced fish to those beaches.

The method essentially accounts for all freshwater variables but there of course remains the big mystery of how those fry will do in the big blue.

Curt