Rail passengers have been warned to expect longer journey times when speed restrictions are brought in on some routes due to forecasts of “extreme rainfall”.
ScotRail said more than a month’s worth of rain is expected to fall in some areas of eastern Scotland between Thursday and 7am on Saturday.
The Met Office has issued a yellow weather warning of rain for eastern Scotland which is in force from 3pm on Thursday until 6pm on Friday.
An amber “heavy rain” weather alert is in force for Aberdeen, Aberdeenshire, Angus and Perth and Kinross from midnight on Thursday until 3pm on Friday, warning some fast-flowing or deep floodwater is likely, “causing danger to life”.
The yellow alert warns of rainfall building up across the high ground of eastern Scotland, with 50-70mm expected and up to 100mm possible across the hills of Angus and Aberdeenshire.
Forecasters said the area covered by the amber warning could see more than 100mm of rain, and even 150mm in parts of the Grampians and Cairngorms.
Network Rail Scotland said it will impose speed restrictions on some routes for safety reasons from Thursday afternoon “due to the extreme rainfall that’s been forecast”, and journey times on those services will take longer.
Parts of the Edinburgh to Aberdeen, Stirling to Dundee and Ladybank to Perth routes will be affected, as will part of the Highland Main Line and the East Coast Main Line between Edinburgh Waverley and Berwick.
ScotRail tweeted on Thursday morning: “Over a month’s worth of rain is expected to fall in many areas across Eastern Scotland between now and 0700 on Saturday.
“For your safety, speed restrictions will come into place later today – check your journey on our app before travelling over the next few days.
“The first route to be affected will be Edinburgh-Dunbar in both directions from 12:00 today.
“Trains will be limited to 40mph (down from 100mph) over a seven-mile section of track, adding around 10 mins to journeys.”
The Met Office yellow warning covers Central, Tayside and Fife, Grampian, Edinburgh, the Lothians and the Scottish Borders, as well as Northumberland in north east England.
Met Office spokesman Oli Claydon said: “We’ve got an area of low pressure that is quite slow moving, the same area of low pressure that brought quite a lot of rain to the south east of the UK today and is now moving up the east coast of the UK.
“Later on Friday that rainfall should start to ease as low pressure moves away.”
Average rainfall for November in Aberdeenshire is 113mm, while for Angus it is 122.8mm, meaning that if these areas do see 150mm of rain, as the amber warning says is possible, more than a month’s worth of rain will fall in the space of just a couple of days.
However Mr Claydon stressed the highest accumulations of rain are only expected across higher ground rather than across the whole of the areas covered by the amber warning.