Can it really be too cold to snow?
PUBLISHED: 17:36 28 January 2019
Archant © 2018
Despite the UK being well known around the globe for its predictably cold weather, forecasting snow is still a big challenge.
Snow could begin to fall in Norfolk overnight on Tuesday and into Wednesday this week as a yellow severe weather warning predicts around 5cm of snow.
In preparation for the possibility of early wintery showers this evening, gritters have been on the road in all areas of the county since 3pm and will remain on standby to grit again at 3am.
But how accurate are these forecasts and what is the ideal weather for it to snow? Can it ever be too cold to snow?
“That is not true, as such,” said forecaster Fred Best, of Weatherquest.
“That phrase comes from ‘colder air hold less moisture’ but it can snow in very cold temperatures,” he added.
What about the old adage of snow not being able to settle on wet ground?
“If it snows very heavily that can still settle,” Mr Best said. “On wetter ground it is harder to settle but with the cold air it can freeze.”
On the accuracy of snowy forecasts, Mr Best said it depended on the temperature on the surface as well as in the atmosphere.
“If the temperature near the ground is colder the precipitation stays as snow,” he said.
“Quite often we use a number of different weather models to predict what could happen and look at what is happening elsewhere.”
According to the Met Office, the cold weather needed for snowfall would require north-easterly winds from the Arctic and Russia to sweep across the UK.
This, coupled with rainfall, could lead to snow but if the rain-bearing weather had time to warm up before reaching the UK it could only take “a fraction of a degree” to make the difference between rain and snow.
Mr Best said Norfolk will see a band of rain pushing in from the west on Tuesday night as the temperature is predicted to drop around -3C in some areas.