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Breaking down how four types of precipitation fell across B.C.’s south coast

Frozen Christmas lights after an ice storm through the Fraser Valley. Janet Bryan / Mission

The forecast has kept some British Columbians on their toes with the weather varying from city to city in the Metro Vancouver region.

For us weather geeks (you know who you are), the conditions have been very interesting over the last couple of days.

We’ve seen everything from rain, to freezing rain, to sleet, to snow across the Lower Mainland and Fraser Valley.

As the system tracked across the region, it shifted from rain to snow. Global News

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But how can one area see so many types of precipitation?

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It happens when a warm, rainy air mass advances over cold air. Warm air is lighter, so it rides up and over the colder, denser air.

The result  — four different kinds of precipitation:

A vertical slice through the atmosphere from Metro Vancouver to Hope showing warm air to the west and cold air to the east. Global News

1) Rain: The entire vertical column is warm. This occurred across much of Metro Vancouver.

2) Freezing rain: The majority of the vertical column is warm but the rain falls through a small portion of very cold air just before hitting the ground so it freezes on impact. This occurred mainly in Abbotsford, Mission and west Chilliwack.

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3) Sleet: Only a small portion of the vertical column is warm. The majority of it is cold. The rain starts off as droplets but freezes on its way down and turns into sleet or ice pellets. Sleet can be loud like hail as it hits windshields and windows. This occurred through much of Chilliwack with strong outflow winds.

4) Snow: The entire vertical column is cold and the precipitation falls only as snow. This occurred in Hope where more than 30 centimetres fell.

Environment Canada issued freezing rain and snowfall warnings for Metro Vancouver on Friday. It also declared a winter storm warning for the Fraser Valley.

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