Potten End Newsletter Article 7

This article originally appeared in the Potten End Newsletter, December 2012.

Potten End Weather

“A snowball in the face is surely the perfect beginning to a lasting friendship.”
― Markus Zusak, The Book Thief

We’re finally in to the winter season with this issue of the Newsletter, and there can be no more obvious subject than snow.

Snow is formed when moist air in the atmosphere is at a temperature of 2°C or less. The moisture in the air then freezes to form tiny ice crystals. These ice crystals collide, join together and form snowflakes. If enough of them join together, they become heavy enough to fall to the ground.

Surprisingly, the heaviest snow falls in the UK tend to occur when the temperature is between zero and 2°C. Above that temperature, the snowflakes melt and fall as sleet or rain.

Snowflakes that fall through dry, cool air will be small and powdery and they won’t stick together. This is the kind of snow that skiers prefer.

At slightly higher temperatures, snowflakes will melt around the edge and join together to form larger wetter flakes. This is the kind of snow that is perfect for making snowmen and snowballs because it sticks together easily.

In Potten End we get snow on average between 10 and 20 days each year, though much of this snow does not settle. Snow does settle and remain on the ground for around 5-10 days each year on average (statistics based on Met Office data from 1971 to 2000).

Fresh-fallen snow settles at a depth of roughly 12 to 1 of equivalent rain. This means, for example, that 30cm (or 1 foot) of snow depth is approximately equal to 2.5cm (or 1 inch) of rain.

Forecasts

It is very difficult to accurately forecast snow for the UK because the UK is positioned between the Atlantic Ocean and mainland Europe and because of the volatile weather patterns we experience.
This means it’s a very fine line between forecasting rain or snow.

White Christmas?

Most people think of a White Christmas as a beautiful white covering of snow falling on Christmas day. The official definition is significantly less romantic in that it involves the observation of a single flake of snow falling at a particular location at any time on 25th December. It’s even less romantic to think that that single flake of Christmas snow may be a part of a thoroughly unpleasant mixed shower of rain and snow. Pity the poor Met Office employee who has to stand outside in the freezing snow watching and waiting for that snowflake! To be honest, we’re pretty sure it doesn’t happen exactly like that!

The chances of this Christmas being White are currently being estimated at around 20% for the country south of Yorkshire/Lancashire. But there is a huge amount of uncertainty around this figure.

Whatever the weather, I wish you all a happy and peaceful Christmas!