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 23/08/2026 · as of: 25/08/2026, 04:35
13 hourly pairs · 3 in melt regime · 0 forecasts resolved · 30 open · 5 stations
By mode and lead time
| n | Bias °C | MAE °C | RMSE °C | |
|---|---|---|---|---|
| Forecast, current hour | 9 | -0.78 | 1.86 | 2.54 |
| Forecast +24 h | 0 | — | — | — |
| Forecast +48 h | 0 | — | — | — |
| Analysis back-hours | 4* | -5.55 | 5.55 | 5.71 |
| Melt regime (excluded) | 3* | 2.19 | 2.52 | 4.09 |
By time of day
| n | Bias °C | MAE °C | RMSE °C | |
|---|---|---|---|---|
| 00–06 | 8 | -2.75 | 3.00 | 3.96 |
| 06–12 | 4* | -0.87 | 2.82 | 3.50 |
| 12–18 | 0 | — | — | — |
| 18–24 | 1* | -3.69 | 3.69 | 3.69 |
By weather situation
| n | Bias °C | MAE °C | RMSE °C | |
|---|---|---|---|---|
| clear | 10 | -3.09 | 3.57 | 4.29 |
| variable | 2* | 0.56 | 1.35 | 1.46 |
| overcast | 1* | 0.60 | 0.60 | 0.60 |
By measuring network
| n | Bias °C | MAE °C | RMSE °C | |
|---|---|---|---|---|
| LWD Tyrol (Austria) | 9 | -0.78 | 1.86 | 2.54 |
| SLF IMIS (Switzerland) | 4* | -5.55 | 5.55 | 5.71 |
By measuring station
| n | Bias °C | MAE °C | RMSE °C | |
|---|---|---|---|---|
| RosskarLWD-SFES2 · LWD Tyrol (Austria) | 5 | -1.23 | 2.79 | 3.34 |
| Ils PlaunsPUZ2 · SLF IMIS (Switzerland) | 4* | -5.55 | 5.55 | 5.71 |
| Mosesgipfel SchneestationLWD-IMOS2 · LWD Tyrol (Austria) | 3* | -0.02 | 0.67 | 0.72 |
| SchöckbichlLWD-NSCH1 · LWD Tyrol (Austria) | 1* | -0.79 | 0.79 | 0.79 |
* 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.