Freezing fog warnings for Norfolk
PUBLISHED: 08:37 18 December 2017 | UPDATED: 11:51 18 December 2017
Archant © 2017
Freezing fog conditions have been forecast for large parts of Norfolk tonight.
Norwich-based forecaster Weatherquest said temperatures could drop to below freezing from as early as 7pm thanks to clear skies across the county.
Forecaster Adam Dury said: “The air will be quite moist which could form mist and fog patches and we expect temperatures to drop below freezing which will lead to freezing fog conditions.”
The Met office also issued a “yellow” warning of fog for the East of England including Norfolk and Suffolk which is valid from 8pm tonight until 12pm tomorrow.
The met office said freezing fog formed in the same way as normal fog when the land cooled overnight under clear skies.
If there are clear skies, the heat radiates back into space leading to cooling at the earth’s surface.
This results in a reduction of the air’s ability to hold moisture which allows water vapour to condense into tiny water droplets eventually leading to the formation of fog.
When fog forms in temperatures that are below freezing, the tiny water droplets in the air remain as liquid.
They become supercooled water droplets remaining liquid even though they are below freezing temperature.
This occurs because liquid needs a surface to freeze upon.
When droplets from freezing fog freeze onto surfaces, a white deposit of feathery ice crystals is formed.
Mr Dury said the ice and fog would remain well in to Tuesday morning.
“Temperatures will only get up to 2 or 3 degrees Celsius in the afternoon but they will continue to rise through the night.
“Milder conditions are forecast for Wednesday and Thursday when the highs reach around 10 or 11 degrees.”