The Hjaltland will sail from Lerwick three hours early tomorrow (Thursday) night due to the weather.
NorthLink said the ferry will now depart for Aberdeen at 4pm.
There is also a “high possibility” the Hrossey will not call into Lerwick on Friday morning.
She is due to leave Aberdeen at 5pm on Thursday, sailing for Kirkwall and then on to Lerwick.
But NorthLink said the Lerwick call was under review due to the forecast.
Friday’s sailings are also set to be reviewed tomorrow.