Transport for NSW is reporting trees down on the Bells Line of Road following storm activity at Mount Tomah on Tuesday afternoon.
Traffic is affected in both directions near Skyline Road.
Parts of Sydney are reported to have been hard hit by sudden thunderstorms, with train lines on the western line blocked by fallen trees.
The Bureau of Meteorology issued a warning on Tuesday morning that gusty thunderstorms would be coming through along with a cold front.
The severe thunderstorms were likely to produce damaging winds across a wide area, including Lithgow, Mudgee, Bathurst, Orange, Oberon and Dubbo.
Wind gusts of up to 72km/h have already been recorded in Lithgow, while Orange has been at 69km/h, Bathurst at 67km/h, Mudgee at 59km/h and Dubbo at 57km/h.