LONDON - Britain's national weather service has upgraded a weather warning for Scotland to its highest level for snow and ice, warning of heavy snow in central Scotland for later in the day on Wednesday and continuing into Thursday.

The extreme weather in Britain has caused hundreds of schools to shut, flight cancellations, train delays and disruption on the roads across the country.

The Met Office announced in its latest warning that heavy snowfall and blizzards due to strong easterly winds will become more widespread across Central Tayside and Fife, southwest Scotland, Lothian Borders and Strathclyde later on Wednesday afternoon, through the evening and overnight into Thursday.

"Roads will become blocked by deep snow, with many stranded vehicles and passengers. Long delays and cancellations on bus, rail, and air travel are expected. Some communities could become cut off for several days. Long interruptions to power supplies and other services," it said.

Amber warnings are also in place elsewhere in Scotland, northern and eastern England, and the East Midlands.

BBC reported that airports including London City, Glasgow and Newcastle have suspended flights as they work to clear snow from their runways. More than 100 flights at Heathrow airport have been canceled.

National Rail also warned that services could face major disruption as a number of train companies have issued warnings of service changes, or disruptions to journeys.

Hundreds of schools and universities were closed and there was significant disruption on the road and rail network as a result of heavy snow. Police are urging people not to travel in the red and amber weather warning areas, which together cover much of the country.

Highways England, which has received numerous reports of stranded lorries, is calling on drivers to reduce their speed and pack a snow kit of blankets, food, water, and a shovel.

Scotland's Transport Minister Humza Yousaf said it was a "difficult day" and that there there had been a "number of issues" with HGVs and cars on the road, particularly on higher ground. "For many, the situation will progressively get worse as the day goes on. "

Stein Connelly, Traffic Scotland's operations manager, has urged Scots to leave work early to avoid the worst of the snow this afternoon and this evening.