A powder day is mostly a logistics problem: the snow falls overnight, the best of it is skied out by 11, and the difference between first chair and a lazy start is whether anything told you to set an alarm.
There’s no sensor at the top of most mountains reporting “powder.” What exists is weather models: Alpy uses Open-Meteo, which assimilates station and satellite data into hourly snowfall estimates for any coordinates — including your resort’s summit. Model snowfall is a forecast-grade number, not a snow stake measurement; resorts’ own morning reports (hand-measured, occasionally optimistic) and model estimates disagree routinely. Alpy shows the model number and names the source, so you know what kind of number you’re reading.
Most alert features mean an account and a push-notification server that knows your resorts. Alpy does it on the phone instead: iOS background refresh wakes the app a few times a day, it checks the forecast for the resorts you follow, and if fresh snow crosses the threshold you set — say 15 cm in 24 hours — you get a local notification. A repeat guard keeps one storm from pinging you every few hours.
The trade-off is honest: iOS decides when background refresh runs, so an alert can land at 06:40 instead of 06:00. The benefit is just as honest: nobody — including us — knows which resorts you follow, because there is no server to tell.
Powder alerts are free in Alpy, with the threshold under your control in Settings. More about the app.