Blog: California’s missing forecast flows in spring 2021 – challenges for seasonal flow forecasting
California’s 2021 water outlook became grimmer this spring as the state did not get fabulous February or miracle March precipitation. Unsurprisingly, spring streamflow forecasts from snowfed basins in the Sierra were far below average. For example, early April forecasts from California DWR called for April-July runoff to be between 59-70% of normal. Bad, but not terrible. Then came April, bringing little additional precipitation. To compound matters, April brought very warm temperatures for much of the state that led to rapid ablation (evaporation) of the Sierra snowpack.