NOUS41 KWBC 261245

PNSWSH



Public Information Statement 25-41

National Weather Service Headquarters Silver Spring, MD

845 AM EDT Thu Jun 26 2025



To:	 Subscribers:

	 ­NOAA Weather Wire Service

	 ­Emergency Managers Weather Information Network

	 ­NOAAPORT

	 Other NWS Partners, Users and Employees



From:	 Richard Bandy

	 Acting Director

	 NCEP/Environmental Modeling Center



Subject:  Soliciting Comments on Proposed Discontinuation of the

North American Mesoscale (NAM) model and other Regional Modeling

Systems to be Replaced by the Rapid Refresh Forecast System

(RRFS) through July 26, 2025.



The Environmental Modeling Center (EMC) at the National Centers

for Environmental Prediction (NCEP) is working towards replacing

the North American Mesoscale (NAM) model, the High Resolution

Window (HiresW) aside from the Guam domain, the High Resolution

Ensemble Forecast (HREF) and the North American Rapid Refresh

Ensemble (NARRE) systems with the implementation of the Rapid

Refresh Forecast System (RRFS) in early 2026.  The NWS is

seeking comments on this proposed change through July 26, 2025.



This transition to RRFS would provide an hourly updating

modeling system over a North America region at 3 km horizontal

grid spacing, which, combined with the model retirements, would

greatly unify and simplify the “convective scale” (approximately

3 km grid spacing) regional models within the NWS operational

modeling suite.



As a deterministic system running to 84 h, the RRFS would fully

retire the NAM, and nearly fully retire the HiresW (aside from

the Guam domain).  As an ensemble forecast system, the RRFS

Ensemble Forecast System (REFS) would fully retire the HREF and

NARRE systems.



The deterministic RRFS generates full domain output at 3 km grid

spacing, and subset grid output over the contiguous United

States (CONUS) and Alaska (AK) (at 3 km grid spacing), and

Hawaii (HI) and Puerto Rico (PR) (at 2.5 km grid spacing).  The

RRFS will also provide output from a separate 1.5 km RRFS fire

weather run, with output provided over a 5 x 5 degree rotated

latitude longitude region.  Details of the RRFS output grids are

available in

https://www.emc.ncep.noaa.gov/mmb/mpyle/rrfs_info/rrfs_grids.txt



Relative differences between RRFS output products and the

proposed-to-be-retired system products will be discussed

individually by the modeling system proposed for retirement.



FOR THE PROPOSED RETIREMENT OF THE NAM:



Both the 12 km parent domain and the 3 km nested domains (CONUS,

AK, HI, PR) would be terminated. The NAM fire weather nest would

also cease to run.



List of NAM output grids being retired (not being utilized by

the RRFS):

https://www.emc.ncep.noaa.gov/mmb/mpyle/rrfs_info/nam_retiredgri

ds.txt



List of NAM nest output grids that will not be retired (being

utilized by RRFS):

https://www.emc.ncep.noaa.gov/mmb/mpyle/rrfs_info/namnest_grids.

txt



LIST OF NAM PRODUCTS NOT GENERATED BY THE RRFS AND DISCONTINUED:



https://www.emc.ncep.noaa.gov/mmb/mpyle/rrfs_info/nam_retirement

s.txt



FOR THE PROPOSED RETIREMENT OF THE HIRESW:



The Guam domain of HiresW will continue to run as in current

operations.



HiresW domains encompassed by the RRFS domain (CONUS, AK, HI,

PR) will be discontinued.



List of HiresW output grids being retired (not being produced by

the RRFS):

https://www.emc.ncep.noaa.gov/mmb/mpyle/rrfs_info/hiresw_grids.t

xt



LIST OF HIRESW PRODUCTS NOT GENERATED WITHIN RRFS AND

DISCONTINUED:

https://www.emc.ncep.noaa.gov/mmb/mpyle/rrfs_info/hiresw_retirem

ents.txt





Products produced by the HiresW, but which will be generated by

the Smartinit system processing RRFS output rather than directly

generated by the RRFS:

https://www.emc.ncep.noaa.gov/mmb/mpyle/rrfs_info/smartinit_prod

ucts.txt



NEW PRODUCTS IN DETERMINISTIC RRFS NOT GENERATED BY NAM OR

HIRESW, AND NOT DESCRIBED IN PRODUCT RETIREMENT/CHANGES TO

EITHER SYSTEM EARLIER:

https://www.emc.ncep.noaa.gov/mmb/mpyle/rrfs_info/rrfs_newitems.

txt



PRODUCTS IN THE RRFS “SUBH” OUTPUT FILE AT 15 MINUTE INTERVALS

FROM 15 MINUTES INTO THE FORECAST TO 18 HOURS INTO THE FORECAST:

https://www.emc.ncep.noaa.gov/mmb/mpyle/rrfs_info/rrfs_15min.txt



FOR THE PROPOSED RETIREMENT OF THE HREF:



The entire HREF system would be replaced by RRFS Ensemble

Forecast System (REFS) products covering CONUS, AK, HI, and PR.



List of HREF output grids being retired due to change in grid

spacing and geographic coverage:

https://www.emc.ncep.noaa.gov/mmb/mpyle/rrfs_info/href_grids.txt



Changes in timing:

- The REFS generates products to 60 h, while HREF only makes

forecasts to 48 h

- While HREF generates products twice daily for non-CONUS

domains (AK & PR at 06Z/18Z, and HI at 00Z/12Z), REFS products

will be generated at 00Z/06Z/12Z/18Z for all regions



HREF TO REFS PRODUCT CHANGES BY OUTPUT FILE TYPE:

https://www.emc.ncep.noaa.gov/mmb/mpyle/rrfs_info/href_product_c

hanges.txt





FOR THE PROPOSED RETIREMENT OF THE NORTH AMERICAN RAPID REFRESH

ENSEMBLE (NARRE):



The entire system would be terminated and replaced by REFS

products covering CONUS, AK, HI, and PR.  The output from the

REFS system will be on the same subset grids produced by the

RRFS (CONUS 3 km, AK 3 km, HI 2.5 km, PR 2.5 km).



NARRE output generated on grid 130 (CONUS 13 km) and grid 242

(AK 11.25 km) will be retired.



Changes in timing:

While NARRE generates hourly updated ensemble products extending

to 12 h, the REFS generates products to 60 h, but only updates

every 6 h.



NARRE PRODUCTS DEFINED DIFFERENTLY WITHIN REFS OR RETIRED DUE TO

NOT BEING GENERATED BY REFS:

https://www.emc.ncep.noaa.gov/mmb/mpyle/rrfs_info/narre_replacem

ent.txt





In addition, all legacy system verification graphics will be

removed from the following website:

https://emc.ncep.noaa.gov/users/verification/regional/



A new RRFS verification website will be created and available

when the RRFS is officially implemented into operations.



Please submit comments regarding the proposal to discontinue

these products to:



Email: rrfs.feedback@noaa.gov

Google Form: Soliciting Comments on the Rapid Refresh Forecast

System Replacing Legacy Systems



National Public Information Statements are online at:

https://www.weather.gov/notification/

