The Met Office has extended its weather warnings for the week ahead amid an icy blast that has brought disruption and several inches of snow to parts of the UK.
The Met Office said temperatures — which are around 5°C-6°C lower than usual for this time of year — plummeted well below freezing overnight on Monday (January 15), the Met Office. The forecaster has issued yellow warnings for snow and ice covering much of the country, which is in the grip of a cold blast of Arctic air.
Meanwhile, the RAC said it expected today (Tuesday, January 16) to be its busiest day of the winter so far for vehicle breakdowns.
So when weather experts talk of snow showers or flurries, what do they mean? We break down all the terminology.
How does snow form?
The Met Office defines snow as "solid precipitation which occurs in a variety of minute ice crystals at temperatures well below 0°C but as larger snowflakes at temperatures near 0°C."
Snow forms when temperatures are low and there is moisture in the atmosphere in the form of tiny ice crystals.
Precipitation falls as snow when the air temperature is below 2°C. It is a myth that it needs to be below zero to snow. In fact, in this country, the heaviest snowfalls tend to occur when the air temperature is between zero and 2°C.
Snow forms through a process called crystallisation within clouds. Here's a basic overview of how snow forms:
Condensation: It starts with water vapour in the air. When the air becomes saturated with moisture, usually in colder temperatures, the water vapour begins to condense into tiny water droplets around particles like dust or ice nuclei.
Crystallisation: As these water droplets continue to freeze and combine, they form ice crystals. The process of water vapor directly turning into ice is known as deposition. This process can happen at temperatures below freezing, even if the air is not completely saturated with moisture.
Snowflake formation: The ice crystals continue to grow as more water vapour freezes onto their surfaces. The specific shape of a snowflake depends on various factors, including temperature and humidity, as the crystals navigate different regions of the cloud with varying conditions.
Aggregation: As the snow crystals fall through the cloud, they may encounter other ice crystals. They can stick together, a process known as aggregation, forming larger snowflakes.
Fall to the ground: When the snowflakes become heavy enough, they fall to the ground under the influence of gravity. The snowflakes can take various forms, ranging from simple hexagonal plates to more intricate and well-known snowflake shapes.
The conditions in the atmosphere, such as temperature, humidity, and the presence of ice nuclei, play crucial roles in determining the characteristics of the snowflakes and the overall snowfall. The entire process is influenced by the complex interactions between meteorological factors within clouds.
What is a snow flurry?
A snow flurry refers to a brief and light burst of snowfall characterised by the presence of numerous small snowflakes falling from the sky.
Flurries are typically short-lived and may not accumulate much on the ground. They are often associated with light, intermittent snow showers and can be part of various weather conditions, such as cold fronts or low-pressure systems.
Snow flurries are common in colder regions during the winter months and contribute to the overall winter weather experience.
What is a snow shower?
A snow shower is a weather phenomenon characterized by a sudden and relatively brief period of snowfall. It is more intense than a snow flurry and can last for a longer duration. During a snow shower, moderate to heavy snowfall occurs, often reducing visibility and leading to the accumulation of snow on the ground.
Snow showers are typically associated with specific weather conditions, such as passing cold fronts, low-pressure systems, or atmospheric instability. They can occur in various climates, but they are more common in colder regions during the winter months.
The intensity of snow showers can vary, and they may come and go rather quickly. Unlike continuous and steady snowfall that might last for an extended period, snow showers are characterized by their more dynamic and changeable nature.
After a snow shower, the weather may clear up, or it may be followed by additional showers or flurries.
Is snow white?
The answer to this is a surprising no, While snowflakes appear to the human eye as a white colour, they are actually totally clear.
The Met Office explains: "The ice though is not transparent like a sheet of glass is but rather is translucent, meaning light only passes through indirectly.
"The many sides of the ice crystals cause diffuse reflection of the whole light spectrum which results in snowflakes appearing to be white in colour."
However, it's worth noting that snow can sometimes take on a bluish or greyish tint. This can occur due to factors such as the angle of the sunlight, impurities in the snow, or atmospheric conditions. In general, though, snow is commonly associated with a brilliant white appearance.
