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Weather updates from site founder Brian Gaze that keep you in the know.

Snow fields to snowdrops in hours

The Chiltern landscape transformed from lush green to a snowy blanket of 6cm, only to return to green again, all within about 12 hours. Snowfields turned to snowdrops in the blink of an eye, showcasing the capricious nature of the British winter. But what caused this dramatic shift?

Cold air covers the UK

Saturday 4th January started with all of the UK under a cold air mass but it was mostly dry. However, weather fronts associated with an area of low pressure were starting to push up from the southwest. Much milder air followed them, but close to the boundary the outbreaks of rain quickly turned to snow. Through Saturday evening and into early Sunday morning about 6cm of snow blanketed parts of the Chilterns. Temperatures hovered around 0°C, creating a brief winter wonderland. 

However, as the weather fronts pushed northwards the much milder air arrived in southern Britain and temperatures started to rise. A thaw of lying snow set in and through Sunday morning it became a very rapid one as temperatures soared to around 12°C!

The contrast in air masses is illustrated in the chart above which shows the situation at 15:00 on Sunday 5th January. The blues over the north of England, Scotland and Northern Ireland highlight the cold air, while the lighter greens indicate the very mild air.

The temperature contrast at the ground level was equally marked as can be seen on the chart below.

In the north temperatures were close to 0°C but in the south they were near to 13°C. The temperature gradient is very steep, with values varying by around 10C over a 50 miles. 

Snowdrops replace the snow

By mid afternoon temperatures were around 12°C in the Chilterns, but in northern England they were still hovering around freezing point. Consequently, the snow melted rapidly and the landscape transformed from snowfields back to snowdrops in a matter of hours. 

The rise in temperatures was dramatic, as shown in the table below. At 9 am it was close to 1°C, but by 2 pm it had climbed to over 11°C, peaking later in the afternoon. Equally dramatic was the rise in dew point. Early in the day it was -1°C, but by the evening it had risen to 11°C, indicating that the air had become much damper.  

Mid-winter to spring all in one day?

The high afternoon temperatures made it feel almost spring-like after the very cold night and early morning. It was a striking example of how quickly the weather can change in the UK. However, a key footnote is that the mild conditions would only last a few hours before cold air returned southwards.

Had the low pressure system and its associated weather fronts followed a slightly different track, temperatures in southern Britain might have stayed close to freezing. Snow could have continued to fall and accumulate, and northern England which became the "sweet spot" for snow, might have remained dry and cold. This highlights why forecasting snow in the UK is so challenging, even at short ranges. The snow area is often very narrow, and minor adjustments to its trajectory can have significant local impacts.