How far ahead can snow be forecast in the UK?
One easy forecast to make is that of some excitable weather headlines about snow. But what’s the reality for forecasting snow in the UK, and do the media headlines get it right?
While snow is obviously more common through the winter months, there are several factors that need be in place for snow to fall in the UK.
Expert meteorologists look at three main indicators when forecasting snow:
Where the air has come from: If air has come from a warmer area, or has spent a long time over mild water, then it would be harder to generate snow. If it’s coming from a cold region, often the north, then there’s a chance of snow being a possibility.
Very heavy precipitation: Most precipitation in the clouds starts off as snow or supercooled raindrops. This often melts before it comes to ground. However, in winter, intense precipitation can keep temperatures lower closer to the ground, increasing the chance of heavy rainfall turning into snow.
When warm air meets cold air: Presenters often talk about weather fronts between warm and cold air. In the winter, these fronts can introduce the moisture and conditions for snow to fall. There’s often a fine line between who sees snow and who sees rain, which is one of the reasons forecasting snow can be difficult.
With a range of factors to consider, forecasting snow accurately in the UK can be one of the trickier forecasts to do accurately.
Forecasting snow in the UK isn’t like some other places along the UK's latitude, where snow can be quite reliably forecast days or weeks in advance.
Because of the UK’s location, where the air comes from is incredibly important when it comes to determining if snow is possible. Being surrounded by water also adds another factor into predicting snow chances in the UK, it may not feel like it if you dip your toe in, but the water in the seas around the UK is well above freezing and that affects the temperature of the air close to the surface which can determine how much snow is in the forecast.
If there is significant snow in the forecast with a good degree of certainty, then Met Office National Severe Weather Warnings will help signal that there could be some impacts.
Snow in the media
Some online headlines make claims of snow often weeks or months ahead of any event, often based on very little meteorological knowledge. But where are they getting the information from?
Forecast models from a range of organisations are available in the public domain for free and sometimes a single model run, often for weather weeks away, gets used by some online outlets to suggest when snow will occur. However, one-off, individual weather charts for weeks away cannot represent a definitive forecast with anywhere near the certainty that some media outlets apply to them.
It’s the job of meteorological experts to capture the nuance between what different charts and models are suggesting, and then to create a forecast that demonstrates the most likely outcome as well as any uncertainties and intricacies.
Working out the details
With so many excitable online media headlines about snow, it can be hard to know what to believe about the forecast. However, when it comes to snow, the headlines often don’t always capture the nuance or uncertainty behind the forecast.
In Met Office forecasts, we try and explain the levels of uncertainty and the reasons for this in our long-form, more in-depth forecasts. These can be particularly useful for those who want to look at likely conditions at a slightly longer range than normal.
For those that want to go in-depth into the weather forecast and the drivers of UK weather, the Met Office’s YouTube series Deep Dive and 10 Day Trend provides insight and explanation on the weather patterns of the UK.