1. Load a wind log
The dump output from a SlopeShift logger (CSV: time,dir,deg,mph).
Lake and sea breezes turn later in the day than slope winds, so the analyzer looks for the switch later: the onshore turn up to 16:00 and the offshore turn up to midnight. Flat schoolyards near water often get a breeze but only weak slope winds.
How it works
Each morning the analyzer takes the steady pre-dawn wind (03:00–06:00) as a baseline, slides a 20-minute average forward, and calls the first lasting change of more than 90° the switch. Directions are averaged as arrows, so north-west and north-east average to north. Evenings work the same way from a 13:00–16:00 baseline. Days without a steady baseline, or with no lasting change, are skipped rather than guessed. These are usually days when the weather overrode the slope winds.
To forecast, it compares each day's switch with the minute direct sun first reached the slope (or last left it in the evening), using the sun's position for your location, the slope and any ridges. The typical lag and its spread become your site's model, and the forecast applies it to the sun's path on any date. Read the science in the SlopeShift article.
Times use your browser's time-zone database. Alberta, for example, stays on UTC−6 year-round from 2026; make sure your device is up to date.