Sailings tonight and tomorrow could be disrupted by a 'rapid deterioration' in the weather.
The Steam Packet Company says the Douglas to Heysham crossing at 7.45pm could be off.
A final decision will be taken by the master at 6.30pm.
The return journey, at 2.15am tomorrow morning, is also at risk.
Weather warning for snow tonight
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Gales put two ferry sailings at risk tonight
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Warning issued over icy roads
High ground could see 4 inches of snow on Saturday night
Mountain Road unlikely to open before Monday
Yellow warning for freezing temperatures tonight