Residents in the Blue Mountains have been isolated after heavy snow blanketed the region.

Authorities have warned commuters that roads have now been closed and there is no access to Sydney.

More than 5CM of snow has hit suburbs including Blackheath, Katoomba and Mount Victoria as locals woke to frosty -8C conditions.

Those who have attempted the 62KM drive into Sydney have been met by a number of traffic incidents that need up closing  Great Western Highway at Katoomba and Mount Victoria. In one of those incidents, a B-Double truck jack-knifed on an icy road.