As part of an ongoing research effort to investigate and develop streamflow forecasting techniques appropriate for large river basins in the Pacific Northwest, a straightforward method has been devised whereby the El Nino Southern Oscillation (ENSO) and Pacific Interdecadal Oscillation (PDO) climate signals can be incorporated into the well-known Extended Streamflow Prediction (ESP) forecasting approach. Forecasts of ENSO are currently available up to a year or more in advance, which facilitates forecasting of the streamflow response to this climate signal at interannual forecast lead times. Additionally, the bimodal phase of the PDO can be identified in real time using a combination of assumed persistence of the existing phase and the tracking of extreme events to identify transitions. The technique we have developed makes use of a gridded meteorological data set to drive the 2-layer Variable Infiltration Capacity macroscale hydrology model at 1-degree spatial resolution over the entire Columbia River Basin above The Dalles. A streamflow forecast ensemble is created by resampling from the historical meteorological data according to six pre-defined PDO/ENSO categories. Each ensemble of meteorological time series (Oct-Sept) for precipitation and temperature is associated with a particular PDO/ENSO category in the historic record. Given a forecast of the ENSO climate signal for the coming water year and the existing phase of the PDO, these meteorological ensembles are then used as forecasts to drive the hydrology model based on the initial soil and snow conditions as of the forecast date. To evaluate the technique, a retrospective forecast of the historic record was prepared (1989-1997) using Oct-Sept as the forecast period, as well as an ensemble forecast for the current water year that could have been delivered on June 1, 1997. Tradeoffs between skill and precision in ensemble forecasts, and the potential for use of this type of forecast for water resources management in the Columbia River Basin are evaluated using the retrospective and current year as examples