Disruptive snow likely on Friday
Cold weather has had a firm grip on the UK for the past week, with temperatures not getting far above freezing by day and many places having their first significant snowfall of the winter.
Temperatures last night dipped well below 0C for many areas, with the lowest temperature, according to the Met Office, recorded at Marham in Norfolk, at -13.4C. This is the lowest temperature of the winter and year so far.
In my blog on Monday, I said that the next potential for significant snow was at the end of this week as less cold air and rain tries to move in off the Atlantic, bumps into the colder air and turns to snow.
Earlier this week, there was a great deal of uncertainty about how far eastwards across the UK heavy snowfall would reach. But now, there are increasingly consistent signals from the weather computer models about the areas most at risk during Friday and Saturday.
Why has there been so much uncertainty?
At the moment, the UK is caught up in a battle ground between very cold air over mainland Europe to the east and less cold, moist air over the Atlantic to the west.
Each time that a set of weather fronts move in from the Atlantic, they bring rain that readily turns to snow as it hits the colder air.
The difficulty that weather computer models have is that they are often overly keen to bring in less cold air from the west too quickly.
Cold air is dense and not easy to move when it has been in place for quite some time, which often means that colder weather can persist for longer than the weather computer models may suggest.
What is likely to happen on Friday?
The latest available information suggests that a fairly active weather front will move in from the west during Friday into Saturday, bringing a spell of heavy snow to much of England, Wales and Scotland.
The main concern at the moment is that the weather front will become slow moving and perhaps even stall, which would mean that some places could see continuous snow, albeit of varying intensity, for 18-24 hours.
Another factor of the weather on Friday will be the strength of the south easterly wind, with sustained wind speeds of 15-25mph at low levels. Over the hills and mountains, this will increase to 25-35mph or more, giving blizzard conditions and drifting snow.
The brisk wind will also force air upwards into the atmosphere more readily over southern and eastern facing hills and mountains, which will increase the intensity of the snow markedly.
How much snow could there be?
However, away from western coastal counties, much of England, Wales and Scotland are at risk from significant snow on Friday. At this stage, Northern Ireland is more likely to have rain and sleet.
The latest Met Office warnings suggest 5-10cm of snow is possible anywhere in the areas mentioned above, with this increasing to 10-15cm over east Wales, the Midlands and north west England, where as much as 20-25cm (8-10 inches) could fall over the hills and mountains here.
As ever, there is still some uncertainty, so it is definitely worth keeping up to date with the forecast to get the latest information as it becomes available.
I’ll be posting further updates here on my blog and also on Twitter – @liamdutton
Graphic source: Met Office