The contrast between this extremely cold air mass and much milder air further south is going to “supercharge” the jet stream. The winds in the core of the jet are forecast to exceed 260mph (418km/h) above the Atlantic.
This huge injection of energy high up in the atmosphere will cause an area of low pressure to deepen rapidly as it heads towards the UK and it is this that brings the threat of gales and disruption on Friday and Saturday.
At this range, several days in advance, there is some uncertainty about exactly how strong the winds will be and exactly where the strongest gusts will occur. At the moment the north-west of the UK looks most at risk – hence the Met Office yellow warning that covers this area.
Outbreaks of rain are also expected and while it will turn milder for some – especially in the south – it will remain cold enough for snow to fall over hills in Scotland, northern England and Northern Ireland.
