During winter, outbreaks of intensely cold air can emerge from polar regions, passing over the relatively warm adjacent oceans. As the lowest layers of the airstream are warmed by the sea, the atmosphere above it becomes ‘unstable’ (meaning warm air is liable to rise up through it). If the air is cold and unstable to a significant depth of the atmosphere, the air can rise vigorously, forming deep snow clouds. The removal of air from the lowest layers of the atmosphere promotes low pressure to form, in turn sucking more air inwards and upward through a tight ascending vortex of strong winds. Blizzard conditions can result, causing disruptive snowfall, especially to coastal areas exposed to the path of the Polar Low.