Freezing rain can make big problems with very small amounts of precipitation. A little glaze of ice is all it takes to turn a familiar route into a slide, bring down branches, and leave homes without heat as the cold air moves in.
The bigger winter storms will feature a combination of snow, sleet, and rain, but the most hazardous part of the mix will be the one that appears to be the least threatening. The forecast associated with this type of storm will feature a lot of snow in the colder areas, along with a band of freezing rain developing where the warmer air is riding above a shallow layer of cold near the surface. This is a very narrow area of transition and may include areas that rarely get ice.
The science of the danger is simple but often underestimated. Snow occurs when the atmosphere remains below 32°F from cloud to ground, allowing snow crystals to remain solid. Sleet and freezing rain begin in a similar way: a snowflake melts into a raindrop as it passes through a warm layer high above. The key is what follows. If the cold layer below is thick enough, the drop will re-freeze in the air and fall as sleet. If the cold layer is shallow near the ground, the drop will become supercooled and freeze instantly on contact, forming a clear layer that can spread across pavement, stairs, cars, power lines, and tree limbs; freezing rain forms an icy glaze that is often invisible.
This invisibility is why bridges and overpasses are often the first trouble spots. It’s because the road surface is cooler than the ground, and the first slippery spots will often show up in places where a motorist least expects them: on ramps, in the shade, and on slight rises where water film re-freezes quickly. Many motorists have reported the loss of traction as being instantaneous because there is no “slushy” stage, as there is with snow.
Ice also puts a strain on the infrastructure that snow often does not. The added weight of the freezing rain builds gradually, and outages can snowball across a neighborhood. It can take longer to repair power outages if lines can’t be reached safely. A half-inch of ice, for example, can mean an additional 500 pounds of weight on power lines, which is why a forecast that is measured in fractions of an inch can still be important.
Preparedness is most effective when it addresses two problems simultaneously: travel becoming unsafe and heat becoming unreliable. Households can prepare by stocking non-perishable food and water for three days, additional blankets and warm clothing, medications, flashlights, and batteries. A weather radio may be useful when cellular service is not available. Some emergency planners also distinguish between supplies for a small “grab and go” bag and a home kit for a longer period of time; the American Red Cross recommends building emergency kits with essentials that can address both problems.
Travel choices offer the greatest safety value. Avoiding the road during freezing rain can lower the risk of accidents and preserve the road for emergency and utility vehicles. In cases where travel is unavoidable, a car survival kit can be useful when delays become hours: water, a blanket, a shovel, a scraper, a flashlight, jumper cables, and simple traction devices. Extreme care is required when temperatures are below freezing and rain is falling.
In the house, winterization measures include fire and carbon monoxide safety, as well as protecting pipes from damage. Working batteries in smoke and carbon monoxide alarms are a must, and heating the house using approved appliances instead of ovens and stoves is important. In extreme cold, drip protection on faucets can keep water flowing, and it is best to disconnect and protect outdoor hoses and spigots to prevent freezing.
Freezing rain is “just rain” until it hits the ground. Once it makes contact, the most important part of the storm forecast isn’t how white the yard is, but how long the glaze remains in place.
