Winter in Norway is cold, bright, and windy. I grew up with it, and I still pack the same way every time the temperature drops. You do not need a huge suitcase. You need layers that work, boots you trust, and a few small things you will actually use.
Pack the suitcase before you zip it
Lay it all out first. I pack thick knit sweaters, warm trousers, a spare base layer, a beanie, and gloves. Wool still works when it gets damp, which it will. A packing cube stops the bulky pieces from taking over the bag. Bring a power bank. You will want your phone at a viewpoint, and the cold drains a battery faster than you expect.
A warm jacket and a real scarf
A long insulated jacket is the piece I wear every single day. Wind along the coast goes straight through a thin coat. Choose a hooded jacket long enough to cover your hips, not a short fashion jacket. A thick knit scarf is not only for the photo. It closes the gap at your neck when you stand still. I wear it loose in town and pulled up when the wind picks up.
Boots with grip
Pretty shoes will not get you across a snowy street in Bergen, or an icy path above a fjord. I want a deep sole, room for thick socks, and a lining that stays warm below zero. Wear the boots before you fly. New boots and a full day of walking is a miserable combination.
The small things
Cold air dries your lips and hands within an hour. Lip balm stays in my jacket pocket, not at the bottom of the suitcase. Hand cream, a spare pair of gloves, and sunglasses belong in the same pocket. Winter sun on snow is bright, even when the air feels freezing.
What it looks like once you are there
Jacket, scarf, beanie, and boots. That is the outfit on a snowy quay in Bergen, with the wooden houses of Bryggen behind you. You can walk, stop for coffee, and still feel warm. Pack for the weather you will stand in, not the weather in the airport.