Pick a resort and you get three ensemble forecasts for it, two weeks ahead — the American model (GFS, 31 runs), the European one (ECMWF, 51 runs) and ECMWF's AI-based model (AIFS, 51 runs), each run many times from slightly different starting data. Where the runs agree, the forecast is trustworthy. Where they spread apart, it isn't. The shaded band on each chart is that spread, so you can read the confidence directly instead of squinting at overlapping lines.
Below the charts are live webcams. If it's dark at the resort — which it usually is for Japan when you're looking from the UK — the cams fall back to the last frame captured in daylight, and the timelapse button plays the day through. There's a summer side too, with 8 places where the questions are heat, rain, storms and wind instead.
A model doesn't update continuously: it runs a few times a day — 00z, 06z, 12z, 18z — from a fresh snapshot of the atmosphere, and takes several hours to arrive after that. Between runs nothing here changes; when a new one lands the charts can shift. Each forecast says which run it is drawn from and when the next is due. Forecast data from Open-Meteo (GEFS 0.5°, ECMWF IFS ensemble 0.25° and ECMWF AIFS ensemble 0.25°).
Total forecast snowfall, added up over the coming week for every resort here, from each of the three ensembles used on a resort's own page — the American model (GFS, 31 runs), the European one (ECMWF, 51 runs) and ECMWF's AI-based model (AIFS, 51 runs). Ranked on GFS; a rough guide for “where's it actually dumping” — open a resort's own page for the day-by-day breakdown and how sure each model is.
Updated Thu 15 Oct, 06:40 UTC