Winter storms can vary in size and strength. It can include heavy snowstorms, blizzards, snow squalls, freezing rain, and blowing and drifting snow conditions. Winter storms can also bring extreme cold temperatures.
Preparation and good decision making are critical to staying safe when winter weather strikes.
On average, northeast and north-central Wisconsin experiences 3 to 5 winter storms a season and a significant ice storm once every 4 or 5 years.
The average date of the first snowstorm in Wisconsin is November 10.
TERMS USED DURING WINTER STORMS
HAZARDOUS WEATHER OUTLOOK
Includes any potential weather hazard out to seven days. It is used for planning purposes.
WINTER STORM WATCH
Issued when there is a potential for a winter storm to affect the region during the next one to three days. It does not always mean the area will experience a winter storm, there is still some uncertainty of the exact path or timing of the event.
– Use this time to ensure you have supplies at home
WINTER WEATHER ADVISORY
These are issued for winter weather events that are more of an inconvenience than a life-threatening situation if caution is exercised. These are often issued when three to five inches of snow, blowing and drifting snow, freezing rain, or a combination of these elements are expected.
WINTER STORM WARNING
Issued when dangerous winter weather is expected, occurring, or imminent. The weather can become life-threatening. Criteria includes six inches of snow or more in 12 hours, eight inches in 24 hours, or lower amounts if accompanied by strong winds or a combination of dangerous winter elements. Avoid unnecessary travel.
This is the most dangerous winter event. Blizzard warnings are issued when snow or blowing snow lowers visibility to 0.25 miles or less, wind gusts hit 35mph or higher, and the storm lasts for three hours or more. Travel is dangerous and should be avoided if possible.
ICE STORM WARNING
Issued when freezing rain will cause widespread glazing. A coating of ice is expected to reach 0.25 inches thick or more on objects and make travel nearly impossible. For lesser amounts of ice, a freezing rain advisory would be used, but even a thin glaze of ice makes travel difficult. Tree branches and power lines can easily snap under the weight of the ice.
SNOW SQUALL WARNING
Issued when brief snow showers reduce visibility to 0.25 miles or less with gusty winds and blowing snow. Cold road temperatures could result in flash freezes and very dangerous travel conditions. Usually reserved for high-impact times.
When snowflakes only partially melt when they fall through a shallow layer of warm air. These slushy drops refreeze as they fall and eventually reach the ground as frozen rain drops that bounce on impact.
When snowflakes melt completely as they pass through a warm layer of air. As it falls through another layer of freezing air, it doesn’t have enough time to refreeze before reaching the ground, but because they are “supercooled” they instantly refreeze upon contact with anything below freezing temperatures. A significant accumulation of freezing rain for several hours or more is called an ice storm.