Thundersnow has been reported in areas such as Perth and Dundee (via Twitter) and for some it's the first time you've heard of it. It is very rare in Scotland, although the most likely area to experience it is across the Northern Isles.
In this case it has happened as the air, which is extremely cold, has come off the continent and travelled across the North Sea picking up moisture and with such a big temperature difference between the sea and air it has provided a lot of uplift and convection.
The air is very unstable as it is so cold, meaning the warmer moist air rising up from the sea can take the moisture a lot higher into the atmosphere and develop large clouds, in this case cumulonimbus clouds. We've seen cloud tops reach 20,000ft on Sunday, where the air is currently around -45C (-49F).
The cumulonimbus clouds can develop a charge difference between the top and the bottom if there is a strong updraft, which also helps to make the cloud larger. This charge difference then creates a bolt of lightning and the thunder is created from the air expanding quickly due to the extreme heat from the lightning bolt.
More thundersnow can be expected in the east of the country on Sunday night and into Monday with deep convection still being created over the North Sea and feeding onto the coast.
The worst of the snowfall during Sunday has been in central and eastern parts of the country with some areas now reporting around 10-15cms of lying snow. Some higher areas have in excess of 30cms.
The band of snow moved a little further north during Sunday afternoon giving areas such as Glasgow and Edinburgh a little rest from the relentless snowfall. At around 3pm the worst of the snow was positioned over Dundee, Angus, Perthshire and Stirling. The whole system will stall here for another few hours before moving back south again tonight bringing the snow back into the Central Belt during the evening.
During the early hours of Monday there will be more heavy falls of snow around Lanarkshire, Edinburgh, the Lothians, Fife, Dundee and Angus. Several more cms can be expected on top of what is already lying.
This overnight band of snow will be easing into England by the time most of us are heading, or at least trying, to get to work but another band of heavy snow will be pushing into Moray, Aberdeenshire and Fife. The snow will then move southwestwards and most central and eastern areas will have more snowfall during the afternoon and right through until at least Tuesday morning.
We already have copious amounts of snow lying in some areas and it is only going to get worse in the next 24 hours with more snow and blizzard-like conditions.
The snowfall on Sunday night and Monday will amount to another 15-20cms of snow in many areas with up to 40cms on higher ground. This added onto what is already lying in some parts of the country means we could well see some higher areas ending up with snow depths of around a metre by Tuesday morning. With strong winds at times deep drifts will also occur.
I would imagine that many villages in central and eastern areas will become snowbound and with snow of this magnitude power loss is also likely in parts of the country.
Temperatures will drop to around -10C (14F) in the towns and cities in the coming week with -20C (-4F) possible in Highland glens.
At the moment it does look as if a bit of thaw could set in later in the week and into next weekend with slight less cold weather arriving for a time. The main problem by next weekend will be ice.
