The Met Office has upgraded a snow and ice weather warning from yellow to amber.
This means the chances of disruption arising from snowfall and ice are now much more likely.
The update was issued shortly after 11:00am on Tuesday.
"Snow showers will be heavy and frequent through the rest of Tuesday, gradually easing off during the early hours of Wednesday, with a further slow improvement expected through Wednesday daytime, as showers become less heavy and less frequent," reads the amber weather warning on the Met Office website.
"Some high ground is likely to see 15-25 cm building up, especially above 200-300 metres. At low levels throughout the warning area, 5-10 cm will be more typical. Showers will be accompanied by hail and lightning at times, while strong winds bring the potential for temporary blizzard conditions and drifting of lying snow, mainly over high ground."
The warning is valid between 3:00pm on Tuesday and 8:00am on Wednesday.