It remains impossible to accurately predict where and when flooding will occur because it is not possible to accurately forecast the weather more than a few days ahead. The amount of rain and variations in temperature over just a few days, for example, can strongly influence the timing and extent of runoff. A combination of weather conditions, including heavy snow and unexpected warm rain, contributed to the historic floods of 1964 and 1996.
The Corps uses both short-term (10-day) and long-term (3-month) runoff forecasts to help determine the amount of space needed in its flood storage reservoirs to reduce flood risks. Year-round, the Corps uses the short-term forecast, produced by the National Weather Service Northwest River Forecast Center, to make the timeliest decisions possible.
The National Weather Service Northwest River Forecast Center is responsible for issuing official flood warnings and forecasts. The public is encouraged to visit their website for information about rising river levels. The Corps uses information on this site to help estimate river flows. Check out: http://www.nwrfc.noaa.gov/.