New Enhancements to the West Gulf River Forecast Center Maps/Front Page


About this Tool

The National Weather Service (NWS) produces a variety of data sets in support of its Hydrologic Services mission. This Google Map-based tool contains many of the data sets necessary to make water resources, flood, and emergency management decisions. The primary goal of this tool is to bring together a variety of spatial data products on the same background map for analysis and decision making. This gives stakeholders the flexibility to create customized maps and the ability to scale maps beyond a single RFC boundary.


Advantages of this tool include:

  • Consolidation of RFC spatial data products into one easy accessible tool available from a web interface
  • Provision of a collaboration and decision making tool for stakeholders
  • Ability to navigate and view products easily across RFC boundaries


To access the National Weather Service - Service Description Document about this tool, please click here.


Using this Tool

To display the legend for any given data overlay, click the legend icon to the right of the specific layer title. Once displayed, legends can be moved anywhere on the display. Each data overlay has a slider bar that controls transparency. Once an overlay is displayed, use the slider bar below the specific layer title to adjust the transparency. This tool is designed to work with all internet browsers. If using Internet Explorer, IE8.0 or later is recommended.


How to Access Flow Information from the Hydrology Decision Support Tool

River Information Tab:
In the River Information Tab, you can access flow information by selecting the Hydrograph (Stage and Flow) Mouse Hover Options.  This will display a hydrograph that displays stage (on the left axis) and flow (on the right access) for the point that you are hovering over.  


Forecast Color Coding and Flow Data Disclaimer

Color Coding of River Forecast Information:

In this experimental product, the color coding of river forecasts is based upon the peak categorical stage that will occur during the forecast duration. There are 5 categories used: no flooding (green), near flood stage (yellow), minor flooding (orange), moderate flooding (red), and major flooding (purple). The forecast duration can vary from location to location and is based on the decision requirements of the local communities impacted at the forecast location as well as the operational capabilities of the NWS.

For locations where forecasts are issued by the Arkansas-Red Basin River Forecast Center (ABRFC), the Lower Mississippi River Forecast Center (LMRFC), the Southeast River Forecast Center (SERFC), and the West Gulf River Forecast Center (WGRFC), the forecast duration varies from 5 to 10 days. At these locations the color coding of the river forecast information will be based on the peak categorical stage that will occur during the forecast duration.

For forecast locations elsewhere in the United States, the color coding is based on the peak categorical stage that will occur in the next two days, regardless of the actual duration of the forecast. At these locations, customers are advised that the full forecast may indicate a higher category of flooding than is coded on the map.

More detailed forecast information is available by using the mouse-over feature displaying the forecast hydrograph or by clicking on a forecast point, which will open the AHPS forecast page for that specific location.

Availability and Use of Stream Flow Information:

Stream flow (or discharge) information is an estimated parameter that is obtained by referencing the rating curve for a forecast location. Rating curves are relationships developed over time between stage height and stream flow, and they are maintained through the acquisition and analysis of manual observations of both stage height and stream flow (or discharge). Rating curves are developed and maintained by the owner of the stream gaging equipment at the forecast location. The NWS does not own stream gaging equipment, and therefore does not develop or maintain rating curves. The NWS has rigorous procedures in place to ensure that the latest rating curve information from the owner of the stream gage is incorporated into the calculation of stream flow information being displayed on the Hydro Decision Support Tool.

Stream flow information is available as an additional parameter at many forecast locations by referencing the right-side scale of the graph. At some locations, the latest stream flow information is also available in the header of the mouse-over pop-up window. In either situation, there may be discrepancies between the stream flow information displayed on the Hydro Decision Support Tool and the stream flow information available from the stream gage owner. Customers are advised that the NWS defers to the stream gage owner to provide the most accurate stream flow information if a discrepancy exists.

Stream flow information may not be available at every location. Some reasons for the lack of stream flow information may be: the inability to obtain manual observations necessary to maintain a rating curve, the complexity of river geomorphology and channel characteristics at a specific location, and the impacts of tides on river stages.

If you would like more detailed information, you can also click on the point and go directly to the Advanced Hydrologic Prediction Service (AHPS) webpage for that site.  The AHPS webpage for that location will display in a separate tab within your web browser.  The AHPS page will have an option under the hydrograph called Tabular Data.  By clicking on this Tabular Data link,  another tab will open which will show the most current stage and flow readings available for the location.

The Hydrology Decision Support Development Team is working towards a solution to incorporate the legacy method of displaying stage and flow information within the mouse hover option.  In the meantime, hopefully the above methods are adequate to access flow information.  If these methods are not desirable, you can still access the legacy map which includes the capability of displaying stage and flow from the mouse-over display. The legacy map can be found at



Downloading the Data Overlays

Each of the overlays that are displayable in this tool is also available for download. NWS products displayed are available for download at:


More Information About the Data Overlays

Current River Status and Forecast:

Observed Precipitation:

National Quantitative Precipitation Forecast (QPF):

National Drought Monitor:

National Flood Outlook Potential:

Storm Prediction Center Convective Outlooks:

National Hurricane Center Tropical Cyclone Information:

FEMA Regions:

FEMA Hurricane Evacuation Routes:

USGS Percent Impervious Areas:

USACE District Information:


Providing Feedback on this Tool

If you would like to participate in a survey on this prototype, please click here.

Alternatively, you can provide feedback on this tool by sending email to: is the U.S. government's official web portal to all federal, state and local government web resources and services.