It will depend on the initial momentum of the train (speed and/or weight) and what type of snow. Powder, like skiers love, will basically blow away. The opposite type is a hardpacked drift in a shallow cutting. The latter has been known to to derail a train, which then stops really quickly.

Yes, deep snow can and does derail trains, though the physics behind it is more complex than simple "blocking." While light, powdery snow is usually swept aside by the train's pilot (the "cowcatcher"), hard-packed or "iced" snow can act as a solid wedge. If a train hits a significant drift at high speed, the snow can become compressed beneath the wheels, effectively lifting the "flanges" (the inner rim of the wheels that keeps the train on the track) above the railhead. Once the flange loses contact with the rail, the train is easily guided off the tracks by the pressure of the snow. In 2026, rail companies in cold climates use massive "Rotary Snow Plows" or "Wedge Plows" pushed by multiple locomotives to clear these dangerous drifts. Additionally, snow can jam "switch points," preventing them from locking correctly; if a train passes over a partially open switch, a "split-point" derailment occurs, which is a major operational hazard in winter.