LIGHT SNOW IN VERY COLD AIR
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METEOROLOGIST JEFF HABY
As air gets colder, in order to stay saturated there will be less moisture in the air. It only takes a small amount of moisture to
saturate very frigid air, such as arctic air with temperatures of -10 F or colder. Because of this, one phenomenon that can be seen
is an almost constant very light snow in arctic air when the air is saturated. This can occur regardless of if there are significant
clouds present or not. The skies can be partly cloudy yet a light snow will continue to fall for many hours. Part of the reason for
this is that very light snow can take a long time to fall from the cloud it originated from to the ground. The low mass and low
density snowflake can stay drifting in the air aloft even at very light wind speeds. Once precipitation ends at cloud level, this
very light snow can continue to fall toward the ground for hours. Another reason is that there could be mixing of warmer air aloft
with the arctic air near the surface. The warmer air with its higher moisture content than the arctic air will quickly saturate
the arctic air. This can condense out then form small flakes of snow that slowly make their way to the ground. The snow may be
so light that very little accumulates on the ground. It may not even be reported in the current conditions since the snow is
so light. It is though not uncommon to see these light snow events with clearing skies when arctic air is present.
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