How does Almanac forecast river conditions?

How does Almanac forecast river conditions?

Almanac forecasts conditions by composing existing weather and hydro inputs — NWS 7-day forecasts, AHPS flow predictions where available, storm-pulse signatures, current lifecycle state, pressure, and SPC context — into per-river projected ratings that roll up to a 7-day Alley Index forecast with confidence and driver phrases. River-condition forecasting on Almanac is a compositional projection of fishability, not a single black-box model that invents cubic feet per second from scratch. The Index Forecast composer synthesizes signals Almanac already collects. NWS forecasts supply precipitation, air temperature, and weather context per river. AHPS hydro forecasts supply a predicted flow trajectory at supported gauges. Storm pulse history supplies peak flow, hours-to-peak, and return-timing signatures. Storm lifecycle state says whether a river is still active or recovering, or is stable. The recommendation scorer maps projected flow, temperature, and clarity into ratings, using a simplified scorer when live history is missing. Pressure and SPC context modify the read for pattern severity. Historical Index baselines supply context for what is normal on that date. For each forecast day, Almanac builds a projected river condition (flow, temperature, and clarity estimates). The projection scorer assigns a rating and score with a breakdown and a target species mode. River scores aggregate into a predicted Alley Index from 0 to 100 for that day, plus confidence and drivers such as flow dropping, precip expected, or clarity clearing. Snapshots are stored so /index/forecast can show a 7-day view. Personal forecast views filter to a user's radius. Sub-daily storm pulse projection handles the "fish before 3 p.m." question. The Index Forecast handles the "which day next week" question.