The 6ft 7in American is the first stage of a recruiting drive by the coach, Vince Macauley-Razaq, who is also signing the former Worthing Bears' American Cleave Lewis.
Macauley-Razaq took over four weeks into the season after sacking Dana Beszczynski, but says Lewis's arrival means he will now stay on, with Lewis also assisting as a coach.
Lewis' debut is delayed by red tape, however. He has had to reapply for a work permit despite first playing in England 12 years ago and signing for Guildford this season.
Derby offer the Royals the rare chance of a win, as the arrival of Powe coincides with the Storm losing American DeRon Rutledge to an ankle injury. Derby have won only two games.
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