From a paper on if God Changes His Mind:

CONCLUSION
Does God change His mind? It all depends. If He has decreed a certain course of action or outcome, then He will not retract a statement or relent from a declared course of action. Verses stat-ing or illustrating this truth must not be overextended, however. Statements about God not changing His mind serve to mark specific declarations as decrees. They should not be used as proof texts of God’s immutability, nor should they be applied generally to every divine forward-looking statement. If God has not decreed a course of action, then He may very well retract an announcement of blessing or judgment. In these cases the human response to His announcement determines what He will do. Passages declaring that God typically changes His mind as an expression of His love and mercy demonstrate that statements describing God as relenting should not be dismissed as anthropomorphic. At the same time such passages should not be overextended. God can and often does decree a course of action.26