Some snow expected – even in southern UK
So far during February, the feel of the weather has probably been the most seasonable it has been all this winter.
The days have had a bit of a chill in the air, there have been frosty nights, as well as a little bit of snow in places – although mainly in the north and over the hills.
During the next two days, there is a chance of snow in some southern parts of the UK, as well as the north.
However, as is often the case here, there’s quite a bit of uncertainty about the detail, with a number of factors that will determine how much snow there’ll be and where.
Where will it snow and how much?
Between now and Thursday, a band of rain will very slowly drift south eastwards across the UK, with some snow mixed in over the hills during the daytime.
There will be two increased chances to see some snow – one for Scotland, Northern Ireland and northern England on Tuesday night, and another for the Midlands, central and eastern England on Wednesday night.
On Tuesday night, rain turning to snow could give 2-6cm over the hills and mountains of southern Scotland, Northern Ireland and northern England, with a slushy covering locally at sea-level.
On Wednesday night, the risk is across the Midlands, central and eastern England, where there could be 1-3cm over the hills and a slushy covering at sea-level.
For both areas, a Met Office yellow “be aware” warning has been issued for the risk of snowfall.
Now, it is worth emphasising that most places will probably see nothing lying on the ground, but there’s a decent chance of at least seeing snow falling – on its own or mixed with rain.
Why is the chance of snow so marginal?
The air through which this band of rain and hill snow is falling is still quite chilly. So as night falls and temperature start to drop, it will potentially become cold enough for rain to turn to snow.
In both cases, snow is most likely over the hills and mountains, as temperature generally decreases with height. So the higher you go, the colder it will be and the greater the chance rain will change over to snow.
Another factor that will be important is the intensity of the rain. When rain falls into chilly air, it can cool it further as the rain evaporates – causing the temperature to drop by a few degrees.
This process is called evaporative cooling and in a marginal situation of rain versus snow, it can be one of the most influential factors.
As a result, don’t be surprised to hear that your friend a few miles up the road had snow, when you just had plain old rain.
Even though any snow is unlikely to be significantly disruptive, large fluffy wet snow flakes could bring poor visibility and slippery surface first thing on Wednesday and Thursday morning in the affected areas.
I’ll be keeping a close eye on the any developments through the rest of today and posting updates on Twitter – @liamdutton