Winter Storms/Extreme Cold – Types and Classifications

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A winter storm is an event in which varieties of precipitation are formed that only occur at low temperatures, such as snow or sleet, or a rainstorm where ground temperatures are low enough to allow ice to form (i.e. freezing rain).  A winter storm can be life-threatening.

Types of Winter Weather Events

The following are the types of winter weather events that can occur:[1]

Blizzards

Blizzards are dangerous winter storms that are a combination of blowing snow and wind resulting in very low visibilities. While heavy snowfalls and severe cold often accompany blizzards, they are not required. Sometimes strong winds pick up snow that has already fallen, creating a ground blizzard.

Ice Storm

An ice storm is a storm which results in the accumulation of at least .25” of ice on exposed surfaces. They create hazardous driving and walking conditions. Tree branches and powerlines can easily snap under the weight of the ice.

Lake effect storms

Lake effect storms are not low pressure system storms. As a cold, dry air mass moves over the Great Lakes regions, the air picks up lots of moisture from the Great Lakes. This air, now full of water, dumps the water as snow in areas generally to the south and east of the lakes.

Snow squalls

Snow squalls are brief, intense snow showers accompanied by strong, gusty winds. Accumulation may be significant. Snow squalls are best known in the Great Lakes region.

Types of Winter Precipitation

Several kinds of precipitation can occur during winter. They are snow, sleet, and freezing rain:

Snow

Precipitation begins as snow and if it doesn’t encounter any layers of air that are above freezing before reaching the ground, it will fall to the surface in the form of snow.

Sleet

If the snowflakes encounter a shallow layer of warm, above freezing air with below freezing air through the rest of the column, then it will partially melt and refreeze into a sleet pellet before reaching the ground.

Freezing Rain

If the snow falls into a deep layer of above freezing air with only a shallow layer of below freezing air located at the surface, (which is often the case with cold air damming,) then the liquid droplets will freeze on contact with any objects (such as trees, power lines, and roads) at the surface that are below freezing.

Cold Rain

If precipitation falls through a large depth of the atmosphere frozen but encounters a relatively deep layer of above freezing air at the surface, then the frozen precipitation may completely melt and have no opportunity to refreeze. Thus, what traveled almost the entire trip to the ground as snow may end up falling as a cold rain instead of anything frozen or freezing

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