Warnings tab¶
The Warnings tab gives a danger level from 1 to 5 for each area and each day, plus the elevation diagnostics that explain it: snow line, zero-degree level, and snow and temperature by elevation.
Provisional
Unless the board says otherwise, the thresholds are provisional. They have not been agreed with a national warning authority. A banner says so. Read a level as "how unusual is this forecast, here, for this time of year", not as an official warning of impacts. Always follow your national meteorological and hydrological service.
The scale¶
Levels follow the European danger-scale colours (MeteoSwiss, EAWS, Meteoalarm):
| Level | Meaning |
|---|---|
| 🟩 1 | No or low danger |
| 🟨 2 | Moderate danger |
| 🟧 3 | Considerable danger |
| 🟥 4 | High danger |
| 🟫 5 | Very high danger |
An area's level for a day is the worst of its hazards. Press the i button next to the heading for the same explanation on the board.
Solid and hatched¶
Each hazard is graded twice: on the deterministic forecast, and on the ensemble's adverse tail (P90 for "too much", P10 for "dropping"). A level only the tail reaches is drawn hatched: same severity, less likely. Where there is no ensemble (and always for wind), levels are solid. That means no information on confidence, not high confidence.
Hazards¶
| Hazard | Graded on | Levels 2 / 3 / 4 / 5 |
|---|---|---|
| Heavy snowfall | new snow in 24 h, above 2000 m | 5 / 15 / 30 / 50 cm |
| Heavy snowfall (3 day) | new snow in 72 h, above 2000 m | 15 / 40 / 70 / 100 cm |
| Heavy rainfall | how unusual for the place and season, with a 10 mm/24 h floor | 0.75 / 1.25 / 1.75 / 2.5 × usual range |
| Dropping temperature | 24 h fall of the daily mean | −2.5 / −4 / −5.5 / −7 K |
| Rising temperature | 24 h rise of the daily mean | 2.5 / 3.5 / 4.5 / 6 K |
| Strong wind | how unusual for the place and season, with a 4 m/s floor | 0.75 / 1.25 / 1.75 / 2.5 × usual range |
Numbers above are the default set. A region may use its own. The i pop-up on the board always shows the set in use.
The value for an area is the area-weighted 90th percentile of its terrain units (10th for dropping temperature): "a good part of the area", not its single worst corner.
Controls¶
- Area level toggle, e.g. provinces or basins.
- Hazard:
Worst hazard, or one hazard at a time. - Basemap (
Topographic,Satellite,OpenStreetMap), Relief, Warning opacity. - ▶ and the day slider, as on the Map tab.
The detail panel¶
Click an area for:
- its level and a Hazards table (amount and level per hazard; "no terrain above 2000 m" where a snowfall hazard cannot apply);
- Snow line & zero-degree level: the elevation where modelled snow cover starts and where the
air is at 0 °C. If the profile does not cross, it says
below the terrainorabove the terrainrather than inventing a line; - By elevation: snow depth and temperature in 250 m bands;
- Next 3 days.
What a level does not tell you¶
- Wind is not gust strength. The model gives an hourly mean over a terrain unit, which runs 20–30 % below station wind. A wind level means "unusually windy for here", not a wind force.
- Temperature changes are smoothed over a whole area and day, much smaller than a station would record.
- No avalanche danger. Snowfall levels are one ingredient. Avalanche danger also depends on snowpack structure, wind loading and terrain. Use your avalanche service's bulletin.
- Snow below 2000 m is not graded by the snowfall hazards.