Model accuracy · graded storm by storm
Which weather model got the snow right?
In the October 2026 Montana, Wyoming and Utah snowstorm (October 9-14, 2026), National Blend (NBM) had the smallest snowfall miss in Southwest Montana three days ahead, an average miss of 4.8 inches across 93 comparison locations, graded against national snowfall analysis. The top models were too close to call.
4070 compares available historical model snow estimates with observer reports and NOAA's gridded snowfall analysis, by region and mountain range, at lead-day brackets 1, 3 and 5. The analysis includes model guidance and is not a resort snow report. When the top models are too close to call, the page says so.
Graded storms
- October 9-14, 2026The October 2026 Montana, Wyoming and Utah snowstorm71 observer reports on the map · 10 models graded
- Southwest MontanaToo close to call, National Blend (NBM) closest
- Rocky Mountain Front & North-Central MontanaToo close to call, ECMWF (Euro) closest
- Northwest MontanaToo close to call, National Blend (NBM) closest
- Northwest WyomingToo close to call, National Blend (NBM) closest
- Northern UtahToo close to call, National Blend (NBM) closest
- Central & Southern UtahToo close to call, National Blend (NBM) closest
Each region's smallest average miss, three days ahead.
How the grading works
Day 1 uses the newest model initialization within the 24 hours before each measurement day starts. Day 3 uses the 48-72 hour bracket before that day, and Day 5 the 96-120 hour bracket. Daily estimates are added over the storm, so later days can use runs initialized after the storm began. These retrospective archive comparisons do not establish when a forecast was available to users.
Town and area estimates use published snow depth where available. Snow-water fields are converted at 10:1; GFS and GEFS estimate snow water from precipitation and a snow-category field. Models without a snow field use precipitation at 10:1. Resort and pass comparisons use height-adjusted historical estimates; ensemble estimates from averaged inputs can differ from Ski Forecast, which converts each member before averaging.
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See every lead day and every resort and town
Members open each graded storm in Model Scorecard: available lead days from 1 to 15, observed or estimated snow beside each model estimate, and the full leaderboard. Model Scorecard also ranks the models at your own saved places.
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Model accuracy questions
Which weather model is most accurate for snow?
It changes from storm to storm and with how far ahead the forecast was made. 4070 grades every storm separately, by region and mountain range, at one, three and five days ahead, and says when the result is too close to call rather than naming a winner it cannot support.
How are the weather models graded?
Historical model estimates are compared with observed or estimated snowfall at the same locations. Town-area rankings use snow observers: CoCoRaHS volunteers, National Weather Service cooperative observers and official weather stations. Mountain and regional rankings use NOAA's National Snowfall Analysis, a gridded estimate built from observations and model guidance. Mountain rankings are checked against NRCS SNOTEL snow-depth gain, which is affected by settling and is not a fresh-snow measurement. Resort snow reports are not used; agreement with the analysis is not independent resort validation.
What does Day 1 mean?
Day 1 uses the newest model initialization within the 24 hours before each measurement day starts. Day 3 uses the 48-72 hour bracket before that day, and Day 5 the 96-120 hour bracket. Daily estimates are added over the storm, so later days can use runs initialized after the storm began. These retrospective archive comparisons do not establish when a forecast was available to users.
Why does an area say "not a snow event"?
Where the reference totals average under an inch of snow, this snow-event ranking does not name a winner. This selection does not evaluate all dry days or all false alarms.