National Weather Service River Forecast Center

I am excited about the possibilities and

Beginning June ,

This expansion of service hours af Stage III afords LMRFC the opportunity to routinely update hydrometeorological/river forecasts as needed and presents an easy transition to 24 hour duty when required. As is normally done during flood situations, additional forecasters will be scheduled during evenings and through the night when deemed necessary. Furthermore, extended duty hours significantly increases continuous forecasting service to our family of WFOs and to external agencies especially during potential/existing flooding situations.

Stage III has two separate processing modes, the hourly and the post analysis mode. The hourly mode generates a merged field of gridded precipitation estimates for radar and

Historically, the NWS has used labor intensive

We have increased the number of locations where we do hydrologic simulations. By simulating stages and flows at these new points, we can shorten the reach for our hydrologic routing, resulting in improved forecasts at downstream locations. We are now modeling flows and stage but not issuing forecasts for the following points: 1) Bogue Chitto at Bush, LA; 2) Wolf River at Landon, MS; 3) Amite River at Grangeville and Magnolia Bridge, LA; 4) South Fork Holston River at Damascus, VA; 5) Little River at Townsend and Maryville, TN; 6) Toccoa (GA)- Ocoee River (TN) System to Dam #3; 7) Tangipahoa River at

The LMRFC has been actively working to expand the number of forecast points through coordination with the appropriate Service Hydrologists. The Service Hydrologists are responsible for establishment of flood stages and development of E-19s for numerous locations. When these actions are complete, the NWS and the LMRFC will begin issuing forecasts at the following locations : 1) Mississippi River at Birdspoint, IL; 2) Mississippi River at Price Landing, MO; 3) Tuckaseege at Bryson City, NC; 3) Sunflower River at Anguilla, MS; 4) Tensas River at Newlight, Tendal, and Clayton, LA; 5) Boeuf River at Fort Necessity and Alto, LA; 6) Bayou Macon near Como, LA. Routine forecasts for these locations should start in 3-6 months.

We will continue to enhance our forecast package and expand forecast segments in our model. The LMRFC will evaluate requests for additional forecast points in our area. Each request will be considered on a case by case basis.

For the last 1 1/2 years, Quantitative Precipitation Forecasts (QPFs) have been provided to LMRFC by all of the Weather Forecast Offices (WFOs) to which we provide service. These QPFs are areal precipitation averages for drainage basins of 100 to 300 square miles. Since forecasters at WFOs are more familiar forecasting with point precipitation instead of mean areal precipitation (MAP) , the HAS unit at the LMRFC embarked on a MAP climatology project last year to help forecasters better understand the range of MAP values over a particular basin.

Using techniques available in the NWS River Forecast System (NWSRFS) , point precipitation is being collected, quality controlled, and processed over a period of 39 years, 1955 to 1993. For this climatological period, MAP is being computed from the point precipitation values using the Theissen method. Over the next year, MAP statistics and graphics will be generated for all of the basins in the

Mean Areal Precipitation statistics can be very useful to forecasters who issue 6 hour QPFs on a daily basis. Using the climatology as a guideline, forecasters will be able to see the probability of exceeding a particular MAP value and the return period of a specific MAP value for a basin. This climatology will allow forecasters to see how their QPF compares with previous events.

An example of a table generated for MAP Climatology is shown on the right. A complete overview of the LMRFC Climatology project, including MAP Climatology findings for two basins, can be seen in the LMRFC MAP Climatology Technical Attachment published in the Southern Region Topics dated October 15, 1997 or visit our web site link, Technical Attachments.