The 26-year-old will sign a short term deal with Town as cover with Tony Crane out for the season and Rob Jones facing a lengthy spell on the sidelines too.
Slade is well aware of Downey's capabilities following their time together at the McAlpine and Slade is hoping the Geordie can make his mark on Town's team.
Slade said: "I have had Glen before and he did well for me. He will bring some cover when we need it and I'm hopeful for his future here."