65 Ice Storms-Mid

Ice Storms FOCUS Question How do ice storms form?

Nature's Icing In some parts of the world, winter weather can create a frozen wonderland of snow and ice. Ponds freeze into solid sheets that support huts for ice fishing. Snow on hills is perfect for sledding. Snow and ice can be fun But they can also be dangerous. Snowy roads can make driving unsafe. Heavy ice can weigh down and snap tree branches and power lines. Many types of winter storms can cover the ground with white snow. An ice storm quickly coats an area in ice. Let's explore how ice storms are different from other winter storms.

How Winter Storms Form Winter storms form when cold and warm air masses bump into each other. In North America, cold dry air from Canada swoops south. Warm, moist air from Mexico moves north. Depending on how they meet, they create a cold or warm front. A cold front forms when cold air pushes into warm air. The warm, moist air rises higher into the sky. Water vapor in the warm air cools and turns into liquid water. Then clouds form Rain falls and thunderstorms may begin.

Warm fronts are more likely to cause big winter storms. That may sound strange, but it's true. During a warm front, warm air moves into an area of cold air. The warm air rises up and flows over the top of the cold air mass. As the warm air rises, it gets colder. The water vapor turns into liquid water or ice. Now clouds form above the cold air. Precipitation, such as rain or snow, falls through the cold air mass instead of in front of it. The type of precipitation that falls depends on the temperature of the air it falls through.

Types of Precipitation Rain often begins as snow falling from clouds above a warm air mass. The snow melts as it passes through warm air. Rain hits the ground. Freezing rain falls when raindrops pass through very cold air. The raindrops become supercooled. They are below the freezing point of 0°C (32°F), but they remain liquid. The drops instantly freeze when they hit ice-cold surfaces. Sleet forms when rain passes through a large area of cold air. The raindrops freeze before landing on the ground as solid bits of ice. Snow falls when snowflakes stay frozen in cold air all the way to the ground.

Frozen Can you guess which type of precipitation falls during an ice storm? Freezing rain falls during an ice. storm and covers every outdoor surface with ice The supercooled raindrops turn to ice as soon as they hit anything below freezing. One drop lands on a tree branch. Ping! It's ice! Another hits a mailbox. Ping More ice forms. A winter storm becomes an ice storm once surfaces are coated with at least 6.6 millimeters (0.25 in.) of ice. Wowser! Ice is heavy Just 12.7 millimeters (0.5 in.) of ice on a power line adds 227 kilograms (500 lb.) of extra weight.