The National Blend of Models (NBM)

At a glance

What NBM is

Every weather model has habits, and some of them are consistent. One runs a little warm, another a little wet, another too eager to deepen a storm. The NBM takes many sources, including NWS models and others, calibrates for them and then blends them. NOAA describes it as a calibrated blend of model output and post-processed guidance.

Version 5.0, implemented on May 5, 2026, adds new inputs, including the ECMWF machine-learning model and NOAA’s AI-GFS, and makes the National Digital Forecast Database elements fully probabilistic on every domain except the oceans. That means the NBM can say not only how much snow is most likely, but how likely a given amount is.

That is why the NBM is useful as a default answer when you want the most likely outcome and not one model’s opinion. It is also why it can look tamer than any single run. A blend averages away a sharp feature that only some inputs show.

Where it does well

• Calibration: biases in the inputs are corrected, so temperature, wind and precipitation are often closer to what is observed than a raw model.
• Probabilities: fields such as the chance of 1 inch or 6 inches of snow in 6 hours, or the chance of measurable precipitation, give you a sense of the odds.
• Fine grid and frequent updates: 2.5 km over the contiguous United States, updated hourly, out to 11 days.
• It is the closest model to a plain-language forecast: one calibrated answer, with odds attached.

Where it falls short

• A blend smooths. If one model shows an extreme storm and the others do not, the blend tones it down. It shows consensus and never a single storm scenario.
• High winds are hard to blend. NOAA changed how version 5.0 computes wind and gusts to address a low bias at higher speeds in the medium and extended ranges, so compare strong-wind forecasts with the raw models.
• It depends on its inputs. If the inputs miss a storm track, the blend will too.
• It cannot explain why. For the reasoning behind a number, open the models that feed it.

What it is typically used for

• Getting the most likely forecast for temperature, wind and precipitation days ahead.
• Checking the odds of a given snowfall amount in 6 hours.
• Seeing how a single dramatic model run compares with the consensus.
• Setting expectations for highs, lows and apparent temperature.

How to see NBM in 4070

The NBM is in Model Explorer under Global Models. It is part of 4070 Pro, which starts with a seven-day free trial.

• Precipitation fields include 6-hour and total precipitation, and the probability of precipitation over 6 and 12 hours, drawn by WDS.
• Winter fields include 6-hour and total snowfall, total ice accumulation, and the probability of at least 1 inch and at least 6 inches of snow in 6 hours.
• Surface fields include temperature and wind, dew point, relative humidity, apparent temperature, minimum and maximum temperature, wind gust and cloud cover.
• Regions include North America, the United States, Alaska, Hawaii and Puerto Rico.

Because probabilities and a blend can hide a sharp scenario, open the GFS, HRRR or the ensembles when you want to see what is behind the number.

How it fits with the other models

Use the NBM as the baseline: what the calibrated consensus says. Then use HRRR for timing in the next day, the GFS and ECMWF IFS for the pattern, and ensembles such as GEFS for the spread. When your own favorite model shows something wild, the NBM is the quickest way to see whether it has company. The guide on the most accurate weather model explains why blends do well.

Specifications change when agencies upgrade their models. The Sources below link to the producing agency. Official National Weather Service forecasts, watches and warnings remain the authority for what is expected where you live.