When will it snow? How many days ahead can the Met Office give an accurate forecast

The Met Office has suggested that swathes of the UK could be set for cold spells next week, while many areas have also been told to brace for possible frost.

But while the official long-range forecast warned of “wintry showers” – including snow – forecasting Britain's weather is rarely a straightforward affair.

Here, Yahoo News UK tries to make sense of things.

How accurately can the Met Office predict snow?

Forecasting snow for anyone, even the Met Office, can be very difficult – one degree warmer or colder can be the difference between a washout and a winter wonderland.

Location can also make a difference. The same type of weather front can lead to snow in some areas at higher elevations, but cause rain at lower elevations.

The Met Office says the UK's terrain makes it more difficult to accurately predict snow that far away, especially compared to other countries where snow can be reliably predicted “days or weeks in advance”. Part of this is down to the fact that the UK is surrounded by water.

Some media reports predicting snow weeks or months ahead will often be based on a single forecast model. However, official forecasters will compare several models before giving a judgment – and that will be combined with reference to the probability associated with a particular weather event.

“It only takes very small changes in temperature to determine if heavy snow is coming down or hitting the mountain tops,” Met Office spokesman Stephen Dixon said.

“What meteorologists look at is where the wind is coming from – is it coming from a cold area that would mean a chance of producing snow?

“When warm air meets cold air in the winter months – this combination can bring moisture, which can allow for snow. But it's usually a fine line between who can see snow and who can see rain over the next few days.”

Is it possible to predict the 'exact date' of ice?

There's a reason the Met Office presents its long-range forecasts for the UK as a whole – there's not much point in trying to be accurate.

Even short-term daily forecasts for the next five days can change in the short term due to small changes in air pressure, temperature or wind direction.

“Forecasts are very difficult to make in the UK, where we have a competitive air force,” Dixon said.

“Those happy headlines that don't capture the fact that predictions of uncertainty make you look forward. If you look a week or two ahead, the date for a certain set of criteria is not the way it works.

“Meteorologists will talk about the level of certainty they have about competing scenarios that may or may not occur.”

How should I prepare for the great British weather?

Maybe pack a big coat (just in case).

What about 'Arctic explosions', 'ice bombs' and 'Beasts of the East'?

The Met Office is getting shy about criticizing some of the “fun” weather headlines from other media.

In September, it went so far as to call one story that the UK was about to be “hit by rain” “rubbish”.

Although we are not against popular media labels, the psychic says that his priority is to accurately reflect the expected conditions.

So while 'Beast from the East' or 'Arctic blast' can logically refer to a particular weather event from a particular location, words like 'snow bomb' should be avoided (unless they have explosives).

Dixon says: “It's not for me to say how some of those articles are written, but what is important to us as an organization is that the language reflects the forecast.

“The 'Beast from the East' can refer to situations, but not to the current point of view. [it should be avoided] and that is true of other words.

“It's important that people understand the weather they're getting and we need to show the uncertainty they're getting – especially when we're predicting snow over long distances. It can be a challenge in communication.”

What is a long-range forecast and how reliable is it?

The Met Office's long-range forecast is divided into two parts, covering 10 consecutive days and 15 periods.

While a short five-day forecast can provide a breakdown by location and even indications of when families in a certain area should expect wind, rain, sunshine or snow, longer-range forecasts cannot provide the same level of detail.

Instead, they provide a general overview of the UK as a whole.

The forecaster made clear the reason for this on its website, pointing out that “small events right now over the Atlantic could have a big impact on our weather in the UK in a few days”.

“As we have cold air, it means there is a continued chance of more of these weather hazards and icy conditions,” Dixon said, reflecting on the current long-range forecast.

“But right now it's very difficult to put into any detail what that might look like next week.”