How big winter storms bring snow, sleet and freezing rain

When big winter storms come, they can bring severe weather, from snow to sleet and freezing rain, or it can be extreme and dangerous cold.

Here are some weather conditions and how they vary from location to location.

How snow turns to ice or sleet on the ground

In order to stick, snow needs a constant stream of cold air from where it forms in the clouds all the way to the ground. If the temperature is below freezing the entire time, the snowflakes will never melt and therefore will not freeze.

“The further north you go, the deeper Arctic The larger the layer, the more likely it is to support the snow,” said and Research scientist Judah Cohen.

Further south, the atmosphere may have a layer of warm air sandwiched between colder layers. This is how sleet and freezing rain happen.

“Snowflakes form, fall, and then they encounter a warm layer, one above freezing, and they melt. But then there’s another layer near the surface that’s again below freezing, so they refreeze before they hit the ground,” Cohen said.

Sleet requires the bottom layer to be cold enough so that the raindrops refreeze when they hit the ground, forming elastic ice particles. If the lower cold layer is shallow, the rain will not have enough time to freeze in the air. Therefore, it falls to the ground in the form of raindrops, which freeze on contact.

Then there’s graupel, a rare mixture of snow and sleet. Not too fluffy, not too hard.

“The snow is trying to melt as it falls, but it hasn’t completely melted yet,” New Jersey state climatologist David Robinson said. Rutgers University. “It stops being a six-point crystal shape and starts looking more like a cotton ball. So it hasn’t reached the point where it’s completely melted and can then refreeze into sleet.”

There’s also hail, which Robinson said some people mistakenly use to describe sleet. But actual hail may not occur during winter storms. This usually happens in the summer because it requires warmer air closer to the surface. This creates updrafts that cause rainwater to rise, freeze, fall, and then rise again to form an ice layer similar to the layers of an onion.

Different precipitation amounts, different hazards

Snow Can be dangerous – enough to send a car sliding into a ditch and endanger lives in heavy snow conditions. But at least it can be farmed.

Ice in the sleet makes moving more difficult.

But the most damaging form of moisture is freezing rain, because it can turn roads into skating rinks and is heavy enough to knock out power lines, Cohen said.

Then comes the extreme cold.

when National Weather Service They will issue an alert if they deem the expected temperatures and wind chills to be low enough to be dangerous.

A cold weather warning means hazardous weather is possible. Extreme cold weather means life-threatening conditions are possible. An extreme cold warning means life-threatening weather is possible.

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