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Sommet

Version 0.9 · 12 Nov 2026

SnowSure’s own forecast engine, built for the mountain, height by height.

Up to nine weather models, rebuilt at three heights on every mountain, and graded every night against snow that was measured.

See your mountainSee the grades
Freezing lineSummit2,085 mMid-mountain1,548 mVillage1,010 m
Limone Piemonte, our home mountain. Rain in the village, snow on top, often on the same day.
ski resorts
500+
weather models
9
weather stations read every day
2,400
stations held out for grading
439

How it works

One mountain, three heights

  1. 01

    The world’s weather models as ingredients

    Up to nine weather models per resort, global and regional.

    Live
  2. 02

    Three heights on every mountain

    Base, mid-mountain and summit, each forecast on its own.

    Live
  3. 03

    Snow made from water, height by height

    Wet snow near freezing, deep powder in the cold, set at each height.

    Live
  4. 04

    The chance of a big day

    The chance of 10, 15 or 25 cm, from 51 ensemble runs.

    Days 1–7 free; days 8–14 with Pro or on My Mountains.

    Live · Pro
  5. 05

    Graded every night, in public

    Scored every night against snow measured at the same height.

    Live

Built on Sommet

Where you see it

Live

Storm Watch

Storms 3–14 days out, the resorts in their path, and how we did.

Live

Local Snow

A daily forecast discussion for your mountain.

Live

Surely, the snow concierge

Ask anything about snow, resorts and trips.

Five questions a day free; unlimited with Pro.

Live

Snow Quality

Light, average or heavy: how wet each day’s new snow is.

Live

Stations

More than 1,100 public stations measuring snow depth.

Live

The public forecast scorecard

Our published forecasts, graded nightly by region. Misses too.

Maps

Maps built for the mountains

From the whole range down to a single slope.

  • Interactive snowfall mapsLive · ProForecast snow across 30 ski regions, day by day.
  • Every resort on the map, five waysLiveEvery resort coloured by forecast, score or recent snow.
  • Live precipitation radarLiveA live two-hour loop, rain and snow in their own colours.
  • SnowSure HD radarLive · ProOur own 250 m radar, a new frame every five minutes.
  • Freezing level, summit wind and temperatureLive · ProFreezing level, summit wind and temperature, day by day.
  • Mountain View in 3DLive · ProYour resort in 3D: runs, lifts, stations and webcams.
  • Slope angle, avalanche terrain and aspectLive · ProSteepness, 30°+ avalanche terrain and which way slopes face.
  • Snow stations on the mapLiveMeasured snow depth at public stations, on the map.
  • Storm mapsLiveWhere the snow line sits as a storm crosses the range.
  • Snow-level mapIn testingWhere rain turns to snow, every three hours for seven days.
Open the maps →
SnowSure snowfall forecast map for the Rockies, 72 hours
Mountain View in 3D terrain, and the snowfall forecast maps for a resort

In testing

Learning from the stations

Each of these runs every day beside today’s forecast and is graded every night at stations it has never seen. None changes what you see until it beats today’s forecast across a whole region.

Overnight low, 1–3 days out: how much closer than the raw modelsNightly grade, 11 Nov 2026, at stations never used for training
  • Alps · 61+34%
  • Cascades · 32+12%
  • All regions · 329+10%
  • Rockies · 154+9%
  • Eastern US & Canada · 57−46%

Right of the line is closer to what stations measured than the raw models; left is further. A region goes live only when it passes, so none has yet.

  • Temperature correctionsHow each model runs warm or cold at each kind of mountain.
  • Precipitation correctionsHow much water really falls, learned from gauges and pillows.
  • Rain or snow, and how deepRain, mix or snow, and how deep, learned from snow boards.
  • Rain or snow by the wet-bulb temperatureRain or snow called hour by hour on the wet-bulb temperature.
  • Snowpack simulationA snowpack model at three heights and nine slope directions.
  • The mountain factorThe extra snow a mountain wrings out of a storm.

What’s next

Sommet 1.0

Sommet 1.0 is the day the first correction learned from stations beats today’s forecast across a whole region, on stations it has never seen, and goes live there. It ships on a grade, not on a date.

Sommet 0.9Sommet 1.0

It ships on a grade, not on a date.

See the grades on Forecast Trust →
A resort in the SnowSure iPhone app: its forecast record, and each weather model's 14-day snowfall beside SnowSure's
SnowSure on Apple Watch: the day’s call for a resort, with its summit temperature

The story

How Sommet got here

From one mountain’s snow reports to an engine that grades itself every night.

2024

  1. A week in Niseko

    Checking the forecast apps every day of a ski week, and finding them generic. The idea starts there.

2025

  1. Snowdata is founded

    Built for our home mountain, Limone Piemonte: rain in the village, snow on top, and lifts that close in the wind.

  2. 27 Nov 2025

    The first records

    Limone’s snow reports logged several times a day, to compare what was forecast with what fell.

  3. Dec 2025

    The resort database

    Resorts entered one by one, each with its base and summit height.

2026

  1. 8 Jan 2026

    Every model, every height

    Each weather model’s forecast stored at base and summit, so each could be scored against what fell.

  2. 15 Jan 2026

    snowsure.ai

    The first version of the website.

  3. 21 Mar 2026

    Graded every morning

    Every forecast scored against measured snow, every day since.

  4. 24 May 2026

    The measured-snow record

    Snowfall measured at weather stations, archived as the yardstick every forecast is held to.

  5. 1 Sep 2026

    Every station, every hour

    Readings from every station we follow, kept hour by hour.

  6. 22 Sep 2026

    Like with like

    A forecast is graded only against a station near its own height, never one in the valley below.

  7. 9 Oct 2026

    Graded as published

    The forecast scored exactly as readers saw it, not as it was rebuilt later.

  8. 29 Oct 2026

    Sommet

    The engine gets its name, and starts learning from the stations: every model captured at 1,700+ stations each morning, in testing.

  9. 12 Nov 2026

    Sommet 0.9

    This page, and its public record at /api/v1/sommet.

Counted on 12 Nov 2026. Sommet’s status is also published as JSON at /api/v1/sommet.