RRFS proposed to replace NAM, HiresW, HREF, and NARRE in early 2026

On June 26, 2025, NOAA/NWS published a proposal to retire several legacy regional modeling systems: NAM, HiresW (except Guam), HREF, and NARRE. The proposal replaces them with the Rapid Refresh Forecast System (RRFS) and RRFS Ensemble Forecast System (REFS) in early 2026. Public comments were requested through July 26, 2025.

What is changing

Deterministic guidance

• RRFS becomes the main 3 km convective-scale model across North America.
• Hourly updates, 84-hour forecast length.
• Full-domain 3 km output plus subsets for CONUS/Alaska (3 km) and Hawaii/Puerto Rico (2.5 km).
• A 1.5 km fire-weather RRFS run is planned for a focused domain.

Ensemble guidance

• REFS replaces HREF and NARRE.
• REFS runs to 60 hours (longer than HREF's 48 hours) with 00/06/12/18Z cycles.

Why it matters

This is a major consolidation of NOAA's regional guidance. If you depend on NAM or HiresW, the switch to RRFS means different physics, resolution, and variable availability. For ensemble workflows, REFS becomes the new baseline for probabilistic convective guidance.

What this means for GribStream users

GribStream already supports RRFS and REFS (experimental), including hourly cycles and convection-allowing resolution. As NOAA finalizes the transition and new feeds become available through the AWS Open Data program, we will expand coverage and provide migration guidance for legacy workflows.

Sources

• NWS Public Information Statement 25-41 (Jun 26, 2025): https://www.weather.gov/media/notification/pdf_2025/pns25-41_RRFS_legacy_model_cessation.pdf