NBM v5.0 proposed for April 2026: major QPF, snow, and AI-input changes

NOAA/NWS announced a proposed National Blend of Models (NBM) v5.0 upgrade targeted for April 2026. The notice solicited public comments through November 21, 2025, and outlined a wide set of product and input changes.

Why it matters

NBM blends guidance from many models into a single calibrated dataset used widely across the U.S. A major version update can introduce step changes in time series, percentiles, and thresholds, which matters for backtests, verification, and operational alerts.

Key changes to expect

Precipitation and probabilities

• Quantile-mapped (QM) QPF and PoP with higher weighting for higher-resolution inputs plus WPC MMEBC (CONUS).
• New 24-hour PMM QPF using only high-resolution models (CONUS and Alaska).

Snow and winter weather

• Calibrated snow exceedance probabilities for 24/48/72-hour totals (CONUS and Alaska).
• Deterministic PMM snow/ice accumulation products (CONUS and Alaska).
• Snow depth and snow-depth exceedance guidance (CONUS and Alaska).

Fire weather and derived fields

• Joint fire-weather probabilities for wind/RH thresholds (multiple domains).
• Probabilistic apparent temperature (CONUS/Alaska/Hawaii/Puerto Rico/Guam) and deterministic apparent temperature (Oceanic domain).
• CAPE percentiles (10th/50th/90th) over CONUS.

Temperature, humidity, and wind

• QM replaces decaying-average methods for instantaneous temperature, dew point, RH, and 12-hour max/min RH, enabling percentiles/exceedances.
• QM 10-meter wind speed and gust guidance added for Alaska, Hawaii, Puerto Rico, and Guam.
• New percentile-picking approach for deterministic wind speed and gusts in several domains.

Input models and resolution

• Higher-resolution ECMWF and Canadian inputs (ECMWF deterministic/ensemble and GDPS/REPS upgrades).
• ECMWF AI/IFS (ECAIFS) added as an input for temperature, dew point, wind speed/gust, and QPF (all domains except Guam QPF).

Timing and access

• Hourly guidance extended from 36 to 48 hours (excluding ceiling, visibility, and thunderstorm coverage).
• NBM GRIB2 data will be available on NOMADS ~30 days before implementation, with an updated SCN issued at least 30 days prior to go-live.

What this means for GribStream users

GribStream already supports NBM. We plan to incorporate NBM v5.0 as soon as the updated feeds are available via the AWS Open Data program. We also support AIFS, which is now a documented input to NBM v5.0, so you can compare AI-driven guidance alongside the blended product.

If you rely on long backtests or threshold-based alerts, plan to:

• Split evaluation windows before/after April 2026.
• Re-tune thresholds for QPF, snow, or wind once v5.0 is live.
• Annotate model-version changes in downstream analytics.

Sources

• NWS Public Information Statement 25-45 (Jul 15, 2025): https://www.weather.gov/media/notification/pdf_2025/pns25-45_soliciting_comments_NBM_v5.0.pdf