raceday.ski continuously compares the calculated snow temperature with real measurements — directly at the measuring stations: 132 IMIS stations of the WSL Institute for Snow and Avalanche Research SLF in the Swiss Alps plus 145 stations of the Tyrol Avalanche Warning Service. Every 2 hours an automatic run computes the model exactly at each station position (station altitude, the station's horizon profile) and pairs it with the measured value — automatically and without preselection. How the calculation works is explained on the methodology page.
Overall picture
Data window: 13/07/2026 to 06/10/2026 · as of: 08/10/2026, 16:01
115 hourly pairs · 17 in melt regime · 24 forecasts resolved · 180 open · 13 stations
By mode and lead time
| n | Bias °C | MAE °C | RMSE °C | |
|---|---|---|---|---|
| Forecast, current hour | 57 | -3.26 | 3.88 | 5.07 |
| Forecast +24 h | 7 | -2.67 | 2.92 | 3.87 |
| Forecast +48 h | 11 | -2.32 | 2.89 | 3.47 |
| Analysis back-hours | 58 | -3.32 | 3.77 | 4.59 |
| Melt regime (excluded) | 17 | 0.43 | 0.84 | 1.88 |
By time of day
| n | Bias °C | MAE °C | RMSE °C | |
|---|---|---|---|---|
| 00–06 | 59 | -3.58 | 3.86 | 4.83 |
| 06–12 | 35 | -3.58 | 4.61 | 5.62 |
| 12–18 | 0 | — | — | — |
| 18–24 | 21 | -2.02 | 2.39 | 3.14 |
By weather situation
| n | Bias °C | MAE °C | RMSE °C | |
|---|---|---|---|---|
| clear | 90 | -4.25 | 4.47 | 5.36 |
| variable | 11 | -0.88 | 2.15 | 2.78 |
| overcast | 14 | 0.93 | 0.96 | 1.10 |
By measuring network
| n | Bias °C | MAE °C | RMSE °C | |
|---|---|---|---|---|
| SLF IMIS (Switzerland) | 61 | -3.98 | 4.37 | 5.11 |
| LWD Tyrol (Austria) | 54 | -2.51 | 3.20 | 4.50 |
By measuring station
| n | Bias °C | MAE °C | RMSE °C | |
|---|---|---|---|---|
| TriftchummeZER2 · SLF IMIS (Switzerland) | 43 | -3.86 | 4.29 | 5.16 |
| RosskarLWD-SFES2 · LWD Tyrol (Austria) | 31 | -1.06 | 2.20 | 2.77 |
| EngstligenalpADE2 · SLF IMIS (Switzerland) | 9 | -5.33 | 5.33 | 5.48 |
| Ils PlaunsPUZ2 · SLF IMIS (Switzerland) | 7 | -2.89 | 3.59 | 4.37 |
| Kappl SinsenergampenLWD-KSIN2 · LWD Tyrol (Austria) | 7 | -2.43 | 2.43 | 2.56 |
| SchöckbichlLWD-NSCH1 · LWD Tyrol (Austria) | 6 | -6.72 | 6.72 | 7.52 |
| Mosesgipfel SchneestationLWD-IMOS2 · LWD Tyrol (Austria) | 4* | -0.25 | 0.74 | 0.78 |
| Tuxerjoch SchneestationLWD-TTUX2 · LWD Tyrol (Austria) | 3* | -11.94 | 11.94 | 11.94 |
| BärgtälliMLB2 · SLF IMIS (Switzerland) | 1* | -5.98 | 5.98 | 5.98 |
| VallasciaVAL2 · SLF IMIS (Switzerland) | 1* | -2.98 | 2.98 | 2.98 |
| Fiss Urgtal SchneestationLWD-FURG2 · LWD Tyrol (Austria) | 1* | -5.73 | 5.73 | 5.73 |
| Burgbach MaucheleLWD-SLBU2 · LWD Tyrol (Austria) | 1* | -2.05 | 2.05 | 2.05 |
| Hochgasser SchneestationLWD-MIOH2 · LWD Tyrol (Austria) | 1* | -0.90 | 0.90 | 0.90 |
* Groups with fewer than 5 pairs are statistically not very robust.
Metrics — how they are calculated
- Error = calculated − measured snow surface temperature (°C), compared at the exact station location (station altitude, flat field, the station's horizon profile — no spatial distance blur). The comparison uses the pure physics calculation of the 3-layer model — before residual correction and before the Kalman station adjustment. Deliberately so: the station correction that is additionally active in the product learns from the very same measurements; including it would flatter the accuracy.
- Bias = mean of the errors (systematic deviation; negative = the model runs too cold). MAE = mean absolute error. RMSE = root mean square error (penalises outliers more strongly).
- Forecast vs. analysis: The headline metric uses only pairs in forecast mode — weather inputs as a user receives them at calculation time. Hours already past are computed with the retrospective weather analysis and reported separately as "analysis back-hours". The skill for +24 h/+48 h comes from archived forecasts that are resolved once the measurement arrives.
- Melt regime: If measurement AND model sit at the melting point (≥ −0.5 °C), the pair carries no error information — it is counted, but excluded from all metrics and shown separately.
- Pairing: Every 2 hours an automatic run compares the model at each active measuring station (SLF IMIS Switzerland, LWD Tyrol Austria) for each full hour. Stations without snow (surface-temperature plausibility check, snow depth below 20 cm) or with anomalous sensor behaviour (automatic quarantine against the network median) are not included.
- Dimensions: time of day in four 6-h windows (local time, identical to the correction windows of the Kalman filter); weather situation from cloud cover (clear < 25 %, variable 25–75 %, overcast > 75 %). The diagnostic tables (time of day, weather, network, station) count all hourly pairs — forecast and analysis; the headline metric only forecast.
Measurement data: WSL Institute for Snow and Avalanche Research SLF (www.slf.ch), licence CC BY 4.0. In Austria, additionally surface-temperature measurements from the Tyrol Avalanche Warning Service — Datenquelle: Land Tirol - data.tirol.gv.at (CC BY 4.0). On Swiss and Austrian ski resort pages, raceday.ski shows the live comparison with the nearest station.
To the wax advisor — or to the methodology: how the 3-layer model calculates and where its limits are.