The Long Range River Flood Outlook (LRO) began as an effort aimed at strengthening the Spring Flood Outlook from the national and regional perspectives. In recent years, NWS leadership and national level stakeholders, such as FEMA and the USACE, have expressed a strong desire for a nationally consistent map displaying long range flood risk at river forecast locations. The requirement was to develop an objective assessment of long range flood risk based on probabilistic river forecasts.

As of May 2018, all 13 NWS River Forecast Centers are routinely generating, consistently issuing, and disseminating LRO information onto the Advanced Hydrologic Prediction Service (AHPS) webpages.

This interactive web page shows the long-range(3-month) risk of minor, moderate and major river flooding at locations where probabilistic forecasts are produced. This risk information is currently based on NWS Ensemble Streamflow Prediction (ESP) probabilistic forecasts which address long-range meteorological uncertainty via climatologically-based ensemble forcing. Over time, this risk information is expected to transition to updated probabilistic forecasts produced by the Hydrologic Ensemble Forecast Service (HEFS), which incorporates weather and climate forecasts and explicitly accounts for the uncertainty inherent in the meteorological predictions. HEFS also accounts for the uncertainty associated with the hydrologic models.

Link to graphical web page: https://water.noaa.gov/

Link to data download (shape file): https://water.noaa.gov/resources/downloads/shapefiles/

Link to metadata

Questions/Concerns about the service, please contact the DISS GIS team.

Time Information: This service is not time enabled.