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NWRFC General Information

Northwest River Forecast Center - is one of 13 National Weather Service hydrologic centers in the United States. This office specializes in flood and water resource forecasting, river modeling, and hydrologic system development. It works with water management agencies to provide the best possible operations of the Columbia reservoir systems. The center is very active in recreational and navigational hydrological forecasting.

Mission: - To save lives and decrease property damage by the issuance of flood warnings and river stage forecasts. Provide basic hydrologic forecast information for the Nation's economic and environmental well being. Provide extended forecast information for water resources management.

Service Area: - The area of responsibility encompasses over 285,786 square miles and includes parts of 7 states and parts of western Canada. It is the second most hydrologic active River Forecast Center in the United States.

Flood Forecasting: - Floods are a natural and inevitable occurrence along the rivers of our country. In the northwest, winter flooding is dominated by heavy precipitation events, while spring flood events result from snowmelt, augmented by precipitation.

The Northwest River Forecast Center uses the National Weather Service Community Hydrologic Prediction System (CHPS) to simulate soil, snow, and stream channel and reservoir conditions. Daily forecasts are made using observations of temperature and precipitation. Forecast of meteorological parameters are included in the river forecast model.

Flood forecasts and warnings are disseminated to the public through Weather Forecast Offices. Forecast distribution is made using the NOAA Weather Radio, commercial radio, television, and local emergency agencies.

Flood Facts:
   --More people die in flood related events than from any other natural disasters.
   --Most flood related deaths occur in motor vehicles.

Water Resource Forecasting: - The demands for fresh water are increasing and more effective management of our limited water resource has become critical. Operations of reservoir systems are growing more complex, involving trade-offs between water supply, flood control, power generation, fisheries, recreation, and environmental concerns. Advanced hydrometeorologic and climatic forecasting techniques are available to reduce the risk as well as to increase the efficiency of water management decisions.

The NWRFC provides water managers water resource information throughout the year. Forecasts of seasonal water supply are prepared monthly from January through June. These forecasts are a useful indicator of either potential flood or drought conditions. They are used by water managers for complex water management decisions.

Water supply forecasts are made available to the public in the publication "Water Supply Outlook for the Western United States." They are also available in local publications produced by the NWRFC and other western RFCs.

Ensemble Streamflow Prediction: - The Ensemble Streamflow Prediction system enables a hydrologist to make extended probabilistic forecasts of streamflow and other hydrologic variables.

ESP uses historical meteorological data to represent possible future conditions. A separate streamflow time series is simulated for each year of historical data using the current simulated conditions as the starting point for each streamflow forecast. The streamflow times series can be analyzed for peak flows, minimum flows, flow volumes, etc., for any period in the future. A statistical analysis is performed using the values obtained from each year's simulation to produce an uncertainty forecast for the streamflow variable.

Meteorological and climatological forecast are included to further condition the statistical distribution.

Hydrometeorological Analysis and Support (HAS): - The HAS functions are designed to capitalize on high resolution data sources and computational power provided by new technologies of the modernized Weather Service. It will bring cohesiveness to the total hydrologic cycle and bridge the gap which has existed between hydrology and meteorology. A staff of three hydrometeorologists at each River Forecast follows:

   --Assimilation of gridded hydrometeorological data sets for the RFC area of responsibility.
   --Assimilation of quantitative precipitation forecasts (QPFs), temperature forecasts, precipitation and temperature outlooks, and forecasts of other hydrometeorological variables for the RFC area of responsibility.
   --Produce daily flood potential discussions and daily hydrometeorological situation discussions.
   --Perform hydrometeorological forecast verifications.
   --Provide for improved communication of hydrometeorological information and support between River Forecast Centers and Weather Forecast Offices.
   --Develop and enhance hydrometeorological techniques.

River Forecast Centers: - The National Weather Service has 13 regional River Forecast Centers (RFC). Each center is within at least one major river system. These centers prepare river and flood forecasts, warnings, and water resource information. Forecast information is distributed to the public through the Service Hydrology Program of the Weather Forecast Offices.

During periods of flooding, the RFCs issue forecasts for the height of the flood crest, the time a river is expected to overflow its banks (flood stage), and the time when the river is expected to recede to within its banks. The RFCs coordinate directly with water management agencies to optimize reservoir flood control space during major flood events.

During non-flood periods, the RFCs make daily streamflow forecasts for water management and prepare seasonal water supply forecasts. The centers provide guidance for a national flash flood program and assist cities in developing local flash flood warning systems. Navigational and recreational forecasts are also produced by some centers.


Acre-foot - The amount of water required covering one acre to a depth of one foot. An acre-foot equals 326,851 gallons, or 43,560 cubic feet.

CFS - In hydrologic terms, Cubic Feet per Second - the flow rate or discharge equal to one cubic foot (of water, usually) per second. This rate is equivalent to approximately 7.48 gallons per second. This is also referred to as a second-foot.

CFS-Day - In hydrologic terms, the volume of water discharged in twenty four hours, with a flow of one cubic foot per second is widely used; 1 cfs-day is 24 x 60 x 60 = 86,000 cubic feet, 1.983471 acre-feet, or 646,317 gallons. The average flow in cubic feet per second for any time period is the volume of flow in cfs-days.

Discharge - In hydrologic terms, the rate at which water passes a given point. Discharge is expressed in a volume per time with units of L3/T. Discharge is often used interchangeably with streamflow.

Flash Flood - A rapid and extreme flow of high water into a normally dry area, or a rapid water level rise in a stream or creek above a predetermined flood level, beginning within six hours of the causative event (e.g., intense rainfall, dam failure, ice jam). However, the actual time threshold may vary in different parts of the country. Ongoing flooding can intensify to flash flooding in cases where intense rainfall results in a rapid surge of rising flood waters.

Flood - Any high flow, overflow, or inundation by water which causes or threatens damage.

Flood Stage - An established gage height for a given location above which a rise in water surface level begins to create a hazard to lives, property, or commerce. The issuance of flood (or in some cases flash flood) warnings is linked to flood stage. Not necessarily the same as bankfull stage.

Flood Warning - In hydrologic terms, a release by the NWS to inform the public of flooding along larger streams in which there is a serious threat to life or property. A flood warning will usually contain river stage (level) forecasts.

Flood Watch - Issued to inform the public and cooperating agencies that current and developing hydrometeorological conditions are such that there is a threat of flooding, but the occurrence is neither certain nor imminent.

Rating Table - This table shows the relation between the gage height and the discharge of a stream or conduit at a given gauging station.

Stage - The level of the water surface of a river or stream above an established datum at a given location.