Why forecasting snow in the UK is a big challenge
There is often a fine line on whether precipitation reaching the ground will be rain or snow, but for now, it may be worth taking forecasts of snow with a pinch of salt.
Thursday 11 January 2024 15:17, UK
There's lots of chatter in the media and online about significant snow which could hit parts of the country from the middle of next week, but in reality, forecasting snow more than two or three days ahead is a big challenge in the UK.
Why is it so difficult?
There is often a fine line on whether the precipitation reaching the ground will be rain or snow, with air temperature being the main factor.
Temperatures of 2C or below can bring snow, with a change of just a fraction of a degree meaning that rain can be seen instead.
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What else has an impact?
Some other things that forecasters look at when determining whether snow will be seen are; location and altitude, including distance from the coast, and precipitation intensity.
Temperatures in cities will typically be higher than in rural areas due to urban heat.
There is also a drop in temperature with height, so areas of high ground are often more likely to see snow than low levels.
In winter, the warmer waters surrounding the UK often keep temperatures a little higher at the coast than would be seen further inland.
Finally, prolonged rain can also turn to snow, with evaporative cooling helping to lower the air temperature around it.
The heavier the rain, the more evaporative cooling that takes place and potentially the greater chance of snow.
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When does the UK usually get significant snow?
The UK's most significant snow events happen when warm, moist air moves in and meets cold air.
But getting the detail exactly right can be frustratingly difficult.
Will there be significant snow next week?
For now, it may be worth taking forecasts of snow for the middle of next week with a pinch of salt.
We do know that a northerly wind will develop on Sunday, allowing cold Arctic air to move southwards.
That will bring snow showers to exposed areas early next week, but after that things become a little tricky.
Low pressure could track across the south introducing milder, wetter weather, which may bring significant snow to parts of England and Wales as it meets the cold air.
That said, knowing the complexities of forecasting snow in the UK, along with computer models showing huge variation, confidence is currently low.