Guide contents
How scores work
Freeze–thaw, crust and slush
How Snowpace decides whether melting and refreezing has left crust, or slush.
When snow melts and then refreezes, it turns to crust. When it melts and stays warm, it turns to slush. The freeze–thaw factor looks at the day and the two days before it.
What counts as a melt
A brief rise just above freezing melts little or nothing: on a calm, clear day the snow surface stays colder than the air. It takes real warmth, held for a few hours, to wet the surface. A frost after that turns it to crust.
What Why? shows
| What happened | In Why? | What to expect |
|---|---|---|
| A melt, then a frost | "Crust from a thaw" when it's holding the day back, otherwise "light crust" | Crust while it's cold, softening as it warms. The bigger the melt, the more it costs. |
| A melt, and no frost | "Slush" | Slush. |
| Little or no melt | "no crust" | No crust. |
| No snow on the ground | Nothing: the snowpack is bare | Nothing to freeze or thaw. |
Crust and slush come with the lowest and highest temperature over the three days, such as "−4°C to 6°C".
What it doesn't know
- The order. A frost before the melt counts the same as one after it.
- The sun. On a sunny slope the surface can melt, and crust, while the air stays below freezing.
- Grooming, which breaks crust up overnight.
For classic and skate, the Surface row follows melt and refreeze hour by hour, assuming normal grooming. Once it has been checked against real days, it's planned to replace this factor for them.
This guide describes Snowpace 1.0.0.