NOUS41 KWBC 221225



Service Change Notice 17-20

National Weather Service Headquarters Silver Spring MD

825 AM EST Wed Feb 22 2017


To:      Subscribers:

         -NOAA Weather Wire Service

         -Emergency Managers Weather Information Network


         Other NWS partners and NWS employees


From:    David Novak

         Director, Weather Prediction Center


Subject: Upgrade to WPC Probabilistic Quantitative Precipitation

         Forecasts over CONUS effective May 10, 2017


Effective Wednesday, May 10, 2017, beginning with the 1800

Coordinated Universal Time (UTC) issuance, the National Centers

for Environmental Prediction (NCEP) Weather Prediction Center

(WPC) will change the Probabilistic Quantitative Precipitation

Forecast (PQPF) products as follows:


- Upgrade all products from the 5-km resolution NDFD grid to a

2.5-km resolution grid which fully covers the Northwest River

Forecast Center basin

- Provide additional probabilistic grids describing the

distribution standard deviation and the 5th, 25th, 75th and 95th

percentile values of the cumulative distribution function

- Issue the 6-, 24- and 72-hour accumulation grids four times

per day


All products will be disseminated on the Satellite Broadcast

Network (SBN), NOAAPORT, and an ftp server in GRIB2 format.


Test grids for the 2.5-km products will be available in GRIB2

format with WMO headers on or about Wednesday, February 22,

2017, on the WPC ftp server:


Upon implementation on May 10, 2017, the 2.5-km grids will be

available via ftp at:



The new 2.5-km resolution data will replace the 5-km products

and reuse the existing 5-km WMO headers. Additional headers will

be allocated to accommodate the new probabilistic grids. A

listing of the WMO headers affected by this change notice is

provided at the URL below:


For questions regarding the implementation please contact:

 James A. Nelson

 WPC/College Park, Maryland



National Service Change Notices are online at: