Greetings!  Is it possible for you to upload several photos of your tree?  We need one close up and one or more that captures the whole tree.  Thanks!  Our next available expert will be right with you.

Hope this helps!! Thank you!!

It is not unusual for large, old willows to lose areas of bark.  The fungal growth in the crevice (picture 3) indicates there is a wood-rotting fungus at work in a portion of this tree.  It is impossible to tell the extend of the wood decay that has developed without some sort of core sampling by a professional arborist.  The risk of portions of this tree coming down in a storm or under a heavy snow load will become very significant as the decay progresses.  If the tree is in a location that would threaten buildings or people were it to fall, removal might be the best course of action.  You may wish to contact your homeowner's insurance representative for their opinion-- they might consider the tree a threat and NOT cover you for any damages that might occur if it falls.