What causes ice instead of snow? When it is cold outside, do you ever wake up to a sheet of ice instead of fluffy snow?
Really, what causes ice freezing rain instead of snow?
Well, it is all about the temperature profile, and maybe a few other factors at play.
We will examine how temperature and atmospheric conditions play a significant role in determining what you will see outside your window on a frigid winter’s day.
Freezing rain or sleet forms instead of snow due to temperature and atmospheric conditions.
What Causes Ice Instead of Snow?
A dangerous winter weather occurrence known as an ice storm happens when freezing rain creates a thin coating of ice over exposed surfaces.
These ice storms are different from snowstorms because, instead of snow, liquid precipitation freezes when it hits cold surfaces.
It is important to learn about different factors contributing to the formation of such storms.
Some of those factors include:
- Temperature profiles
- Precipitation formation
- Atmospheric conditions
- … and more!
Let’s talk more about these to get a better idea of what leads to the formation of ice instead of snow.
The atmospheric temperature profile strongly influences what kind of precipitation actually falls to the earth.
Snow is the most common kind of precipitation when air temperatures are below freezing along the whole atmospheric column, from the cloud tops to the ground.
Freezing rain and sleet are types of precipitation that can fall when the temperature difference between the cloud base and the ground is greater than zero.
Fact: The ice storm usually lasts a few hours but can extend to several days, and its after-effects can be even more long-lasting and damaging.
An ice storm’s temperature profile has a distinctive shape.
There is a shallow layer of cold air (below freezing) near the ground, and a warmer layer of air (above freezing) in the atmosphere above it.
As snowflakes forming in the colder upper atmosphere reach the warmer lower atmosphere, they melt and eventually fall to the ground as rain.
While the rain continues to fall, some of the drops will reach the subfreezing temperature zone close to the ground.
However, the raindrops do not have enough time or distance to form into ice pellets before reaching the surface; therefore, they cannot be mistaken for sleet.
They continue to exist as supercooled liquid droplets, though.
These supercooled droplets rapidly freeze and produce shiny ice when they come into contact with exposed surfaces like trees, electricity wires, roadways, and cars.
What Causes an Ice Storm Instead of Snow?
There are a number of potential causes for the unusual temperature profile needed for an ice storm to form.
Some of the most important ones are listed here:
Changes in Temperature
As mentioned already, the temperature profile of the atmosphere has a role to play here.
The requisite temperature profile for an ice storm can be put in motion by the advection of both warm and cold air masses.
As a low-pressure system moves in from the south, it can pull warm air north ahead of it while forcing cold air southward.
Freezing rain can form when these air masses collide, providing the right temperature structure.
While warm air aloft can form when surface cold air is overcome, cold air trapped near the ground keeps temperatures below freezing.
The terrain has a role in how long it takes for an ice storm to develop.
Ice storms are more common in valleys and other low-lying places because cold air is thicker and prefers to settle there.
The temperature profile necessary for an ice storm can be fostered by the movement of warm air over a cold, shallow layer.
Similarly, elevated areas, such as mountains, can also operate as a barrier, retaining cold air on their windward side and fostering ice storm conditions.
There may be a correlation between the weather just before an ice storm and the severity of the storm itself.
The likelihood of ice formation from freezing rain increases when surfaces have been preconditioned to be at or below freezing by prolonged periods of cold.
If the weather is mild before an ice storm, less ice may form on the ground and other surfaces since they will be above freezing.
Large-scale weather patterns can generate atmospheric conditions favorable to the development of ice storms.
For instance, a robust high-pressure system located to the north or northeast of a low-pressure system can direct frigid air toward the warm sector of the low-pressure system.
This frigid air can become entrapped beneath the milder air associated with the low-pressure system, thereby establishing the required temperature profile for freezing rain.
Fact: Ice storms can lead to ice jams caused by the large chunks of ice breaking and jamming natural obstructions, and often leading to severe flooding.
Location and orientation of frontal boundaries can play an important role in forming ice storms.
Stationary fronts, where chilly and warm air converges but do not advance substantially, can be conducive to freezing precipitation.
Warm air is compelled to rise above the colder air at the surface, producing the requisite temperature structure for an ice storm.
In addition, the sluggish movement of these frontal boundaries can result in extended periods of freezing rain, thereby increasing the likelihood of significant ice accumulation.
The atmosphere’s stability can affect the chances of ice storm formation.
A stable atmosphere in which the temperature increases with height in the balmy layer can promote the thawing of snowflakes and the formation of freezing rain.
In contrast, an unstable atmosphere with temperature inversions can disrupt the required temperature profile for an ice storm and reduce the likelihood of freezing rain.
The physical processes that occur within clouds might influence the possibility of an ice storm developing.
The presence of supercooled liquid water droplets in clouds can hasten snowflake melting, increasing the risk of freezing rain.
The size distribution of snowflakes and liquid droplets in the cloud can also affect melting efficiency and the possibility of freezing rain.
Ice storm formation can be affected by the time of day and the season.
Surfaces are more likely to be at or below freezing during the winter months, when daylight is scarce and solar radiation is feeble.
This raises the likelihood of ice formation during freezing rain episodes.
During the warmer months, surfaces are less likely to be cold enough for freezing rain to produce ice, lowering the likelihood of ice storms.
Furthermore, when temperatures are normally the coldest, ice storms that occur overnight might have a greater impact than those that occur during the day.
Are There Any Warning Signs of Ice Storms?
Ice storms are meteorological occurrences that can inflict considerable infrastructure damage as well as hazardous circumstances for transportation and human safety.
Early detection of ice storm warning indicators can assist individuals in preparing for and protecting themselves, their family, and their property.
Here are some possible ice storm warning signs:
Meteorologists regularly study atmospheric conditions to forecast the risk of ice storms.
They issue ice storm warnings, watches, or advisories based on numerous weather models and data.
Pay close attention to local and national weather forecasts to keep updated about potential ice storm hazards.
Fact: The production of ice on trees, power lines, and other high surfaces can be an early warning sign of an ice storm.
Ice storms occur when the air temperature is at or below the freezing point (32°F or 0°C).
Watch temperature variations, especially throughout the winter months, to detect potential ice storm threats.
Rain or Drizzle
The presence of rain or drizzle with surface temperatures below freezing may signal the start of an ice storm.
As raindrops fall through a chilly layer of air near the ground, they can freeze on impact with surfaces, resulting in freezing rain.
Frost on surfaces such as vehicles, trees, or sidewalks can be an early warning sign of an impending ice storm.
When frost begins to build, it is critical to be wary of slippery conditions and prepare for the likelihood of an ice storm.
Fact: Check barometric pressure fluctuations and be on the lookout for unexpected decreases, which could indicate the onset of an ice storm.
What causes ice instead of snow?
When certain temperature profiles and atmospheric variables come into play, ice instead of snow is formed.
There are a number of variables, including terrain, weather patterns, and the development of precipitation affecting the likelihood that you will come across ice or snow.
Knowing these things and keeping up with weather forecasts is crucial for preparing for ice storms, which can cause damage to buildings and threaten lives.