The model

The Rapid Refresh Forecast System (RRFS) is NOAA's new convection-allowing model, built on the Unified Forecast System's FV3 core and the successor to the HRRR. It runs a single 3 km grid across North America and starts a new run every hour. Every hour's run goes 18 hours with 15-minute output; every third hour's run publishes the full hourly files to 18 hours; and the 00, 06, 12 and 18 UTC runs go out to 84 hours. It becomes NOAA's operational model on 6 October 2026 at 12Z.

The ensemble

At 00, 06, 12 and 18 UTC the RRFS also runs as an ensemble, each member started from slightly different conditions to show what the forecast is sure of and what it is not. NOAA publishes five of those perturbed members, m001–m005, to 60 hours. Together with the deterministic run (the ensemble's control) that makes six members, and adding the previous run's six, aligned by valid time, makes the twelve-member time-lagged set this site shows by default. NCEP's own ensemble products (REFS) blend fourteen members; those probabilities come to this site next.

How Forecast Fresh works

A dedicated server in the same data centre as this site watches NOAA's public RRFS bucket every five minutes. For each member and hour it reads the file's index and fetches only the 38 records it needs (about 33 MB of a 48 MB file, in a dozen byte-range requests), decodes them, turns the winds from the model's grid to true north and south, and files 35 variables at the model's native 3 km resolution. A whole run, all six members and 61 hours, takes about a minute and a half.

Everything is stored twice. The spatial copy keeps each member-hour as a whole map, for maps and area statistics. The time-series copy is the same numbers transposed, so that every member's forecast for one spot sits together on disk: a pinpoint reads three small blocks per variable instead of 366 maps, and answers in well under a quarter of a second. The time-series copy is built in 21-hour blocks as soon as all six members have them, so the first day of plumes appears long before the run finishes. The newest eight runs (two days) stay on fast disk; the verification subset goes to a long-term archive.

Values on the pinpoint page are the model's own at the 3 km grid cell containing your point: no smoothing, no bias correction, no blending with other models. Forecast Fresh is here to show RRFS as it is. Corrected and blended forecasts will be labelled as such when they arrive.

What is next

The Maps are live: the grads3 native kernel from the RRFS Creator Toolkit draws 94 products for the lower 48, Alaska and North America every hour of each 00/06/12/18Z run, and a dozen regions every three hours. Next: ensemble maps from the members already in the store (any member, any threshold, on demand); a storm tracker that follows rotating storms through every member's 15-minute updraft helicity; verification of every run and member against surface observations, URMA and MRMS, feeding Forecast Scores; and, once the archive is deep enough, a bias-corrected RRFS and a blend with the rest of the fleet. Alaska, Hawaii and Puerto Rico follow the lower 48.

Credits

Model data: NOAA/NCEP, through the NOAA Open Data Dissemination program (noaa-rrfs-ops-pds). Place names: Forecast Points' gazetteer. Forecast Fresh is part of the Forecast Network with Forecast Eagle (national model maps, including RRFS and REFS), Forecast Points (point forecasts from NDFD, NBM and more) and weather.city.