An emergency warning for a 400-hectare bushfire in Victoria's Grampians National Park has been downgraded.

Victoria's Country Fire Authority (CFA) scaled back the warning for the Jensens Road area of Mirranatwa to a watch-and-act alert on Sunday night.

It says the fire is about 30 kilometres north of the Dunkeld area and is moving slowly in a southly direction.

The CFA says residents in Mirranatwa and Dunkeld should stay aware of the fire's movements through local radio, saying the emergency alert could be issued again throughout the night.

Earlier in the day difficult weather conditions hampered firefighters' efforts to contain the blaze.

Residents are advised to check their bushfire survival plans, prepare and remain alert. Those without a plan should still leave the area if the path is clear.