A circular polarizer can help in snow photography, but it’s not essential.

What it can do well:

• reduce some reflections from ice and shiny snow at certain angles
• cut atmospheric haze and make a clear sky look deeper blue

Possible downsides:

• the sky can become unnaturally dark depending on your angle to the sun and composition
• it costs light, which may not be ideal for fast action
• it can slow you down if you need to keep adjusting it on the slopes

In practice, it depends on the shot. If glare from snow or ice is distracting, try the polarizer. If the sky gets too dark or uneven, take it off. If there’s little sky in the frame, the darker sky may not matter. If the sun is behind you, glare may be less of an issue anyway.

So: useful sometimes, not a must-have. For winter sports, many photographers shoot perfectly well without one and prioritize speed and flexibility. If you want motion blur or wider apertures in bright snow, an ND filter may be more useful than a polarizer.