Current practices and future challenges in communicating hydrologic forecast uncertainty at the Colorado Basin River Forecast Center

Like most River Forecast Centers in the National Weather Service (NWS), the Colorado Basin River Forecast Center (RFC) operationally releases streamflow and hydrologic forecasts for a range of lead times. At monthly to seasonal lead times, these forecasts are probabilistic, created in part using model-based ensemble hydrologic prediction techniques. Information products derived from these forecasts communicate a range of uncertainty reflecting the skill of the forecasts. In contrast, shorter lead (e.g., hours to days) forecasts that provide a basis for flood warning and spring snowmelt peaks are deterministic. Information products derived from the deterministic forecasts, which include flood watches and warnings released to the public, currently do not contain quantitative estimates of uncertainty. Recent research and development efforts at CBRFC and elsewhere in the NWS are exploring ensemble-based, probabilistic forecasts for the short, traditionally deterministic lead times. This presentation discusses both the current contrasts in communicating uncertainty between the different kinds of RFC forecasts, and the challenges involved in migrating toward probabilistic forecasting across all time scales.