When NWSRFS, SEUS, and snow intersect

The National Weather Service River Forecast System (NWSRFS) is being implemented for river and water supply forecasting operations by the National Weather Service in the Pacific northwest. The initial process of calibration has been performed only by optimizing on the observed streamflow rather than on snow observations. The Snow Estimation and Updating System (SEUS) is a postprocessor which permits snow observations to be incorporated to update model states as the season progresses. The applicability of the NWSRFS suite of programs for water supply forecasting will be impacted by (1) reliability of data observations, (2) the cognitive value of the snow and soil moisture accounting conceptualizations, (3) the effect of daily operational changes ('modifications') made to the model to keep it tracking observed st;reamflow, and (4) the 'connectivity' between SEUS and the realism with which the snow simulation duplicates reality. An example of Dworshak Reservoir (Idaho) inflow forecasts suggests thetechnique is very promising despite difficulties.