There are now 55 uncontained bushfires across the state, with extreme fire danger forecast for the Southern Slopes.
Another nine blazes - including the massive Dunns Road and Border fires - were at watch-and-act level on Friday evening, with most in the state's scorched southeast.
The blaze jumped Jingellic Road at Lankeys Creek and is moving to Mundaroo, Tumbarumba and Mannus.
"Hopefully, we will not see more thunderstorms and more dry thunderstorms and lightning strikes causing new fires", NSW Rural Fire Service Commissioner Shane Fitzsimmons told the media on Saturday.
The Erskine Creek fire was burning out of control to the south of Wentworth Falls and a forecast southerly change was predicted to hit between midnight and 2:00am (local time).
The southwesterly wind change brought gusts of up to 90km/h across the Riverina, with the Bureau of Meteorology warning the change will be "particularly gusty" and "very significant" across the state.
It will blow up the coast throughout the evening and was expected to reach Morouya about 11pm and Sydney by 2am on Saturday.
A firefighter in his 20s has been hospitalised and is in a stable condition after he suffered burns to his face in the Snowy Valley region when fierce winds pushed the fires in different directions.
At Thredbo, snowmaking machines have been running non-stop for days to wet village grounds to combat any potential spot fires from the Pilot Lookout fire south of the ski resort.
Elsewhere, a "mega-blaze" formed around 9:00pm as severe weather conditions fanned fires in the Snowy Mountains area.
NSW Premier Gladys Berejiklian said the extent of the damage wouldn't be known until later this morning.
"In essence, we know it's going to be a long and hard night", Ms Berejiklian said.
The RFS added there were 147 bush and grass fires burning across NSW - 65 uncontained - as of 6am AEDT today.
Communities on the Victoria-NSW border were also warned they may be unable to contact triple zero due to telecoms outages.
Conditions have eased across most fire grounds, with only 1 fire at watch and act warning in place.
Australian Defence Force national coordinator Major General Jake Ellwood on Friday said just under 2000 reservists are on duty to provide support during the bushfires.
"It would appear that we have got at least a week, it will probably be the best seven days we have had without a rise of very unsafe fire ratings", said the NSW fire chief.