The five-star Armstead, who is Scout.com's No. 1-rated offensive tackle in the 2012 class will announce his decision Sunday at 3 p.m. (PST) at The House of Christian Church in Sacramento.
The Irish were nearly out of the running last week but rallied and are now back in the fold and have a legitimate shot in the sweepstakes.
There are a few added twists is the situation, beginning with Armstead's desire to also play basketball, which schools are willing to accommodate.
Also, his brother, Armond Armstead, is at USC but planned to leave and enroll in January with Arik. However, when a decision couldn't be made, Armond decided to stay with at USC for the springand will transfer in the summer.
Whether the Irish are still heavily involved with Armond is not known.