A Fernie snowfall warning is in effect, with 25 to 35 cm of new snow expected by Thursday morning, and around town that usually means one thing: the unofficial “20 cm rule” is about to come into effect.

For the uninitiated, the rule is simple. When the forecast says 20 centimetres or more, plans quietly change. Meetings get “moved.” Emails get delayed. And a noticeable number of people suddenly develop a strong interest in heading toward the mountains.

Environment Canada says a low-pressure system moving through the southern interior tonight will bring heavy snow, strong winds, and blowing snow to the Elk Valley. Snow will intensify this evening and continue overnight as a cold front moves through the region, with wind gusts reaching up to 70 km/h and periods of reduced visibility in blowing snow.

By Thursday morning the heaviest snowfall should ease, though gusty winds and scattered flurries are expected to continue through the day.

While storms like this make powder seekers smile, they can also make travel unpredictable. Highway 3 and surrounding valley roads could see reduced visibility and drifting snow, particularly overnight when the winds pick up.

Still, longtime Fernie residents know the routine. When a storm like this rolls in, the town settles in for a snowy night and waits to see what morning brings. Sometimes it’s a shovel. Sometimes it’s a snowblower. And sometimes it’s drop everything and head to the mountains.

If the forecast verifies, Thursday morning could be one of those mornings where Fernie wakes up looking like winter did exactly what it’s supposed to do.

And if that total creeps past 20 centimetres… well, the rule says you know what happens next.